Add UMA stats for audio/video containers.

media/base/container_names.cc

Index: media/base/container_names.cc
diff --git a/media/base/container_names.cc b/media/base/container_names.cc
new file mode 100644
index 0000000000000000000000000000000000000000..73279d6a8a7d521ab1cfa6c06a02a2e2e63dcd9c
--- /dev/null
+++ b/media/base/container_names.cc
@@ -0,0 +1,1993 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/base/container_names.h"
+
+#include <cstdio>
+
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+
+namespace media {
+
+// Template to extract array size.
+template <typename T, size_t N> inline size_t size(T(&)[N]) { return N; }

[Ilya Sherman, 2013/04/29 23:48:06]

Any reason not to use the shared arraysize macro defined in base/basictypes.h?

[jrummell, 2013/04/30 21:36:50]

Done.

+
+#define READ16(p) \
+    (((uint32_t)((const uint8_t*)(p))[0] <<  8) |    \
+                ((const uint8_t*)(p))[1])

[Ilya Sherman, 2013/04/29 23:48:06]

Please use C++-style casts, rather than C-style casts.  Also, it seems really
likely that this code already exists somewhere in base, perhaps under
base/strings/string_number_conversions.h.

[jrummell, 2013/04/30 21:36:50]

Unable to find a similar function in base. Converted them to inline functions
for better type checking.

+#define READ24(p) \
+    (((uint32_t)((const uint8_t*)(p))[0] << 16) |    \
+               (((const uint8_t*)(p))[1] <<  8) |    \
+                ((const uint8_t*)(p))[2])
+#define READ32(p) \
+    (((uint32_t)((const uint8_t*)(p))[0] << 24) |    \
+               (((const uint8_t*)(p))[1] << 16) |    \
+               (((const uint8_t*)(p))[2] <<  8) |    \
+                ((const uint8_t*)(p))[3])
+
+#define TAG(a, b, c, d) \
+    (((uint32_t)(a) << 24) | ((uint8_t)(b) << 16) | \
+      ((uint8_t)(c) << 8) | (uint8_t)(d))
+
+// The strings in the list below are the ones returned by FFmpeg.
+// This would be the string from AVInputFormat.name. The list is
+// sorted by string alphabetically, so that we can use a binary
+// search when looking for a container by name.
+const ContainerNameMapping ContainerNames::container_name_mapping[] = {

[Ilya Sherman, 2013/04/29 23:48:06]

Any reason not to tuck this into an anonymous namespace, rather than having it
be a static class member?

[jrummell, 2013/04/30 21:36:50]

This is used by the unittests to verify it is sorted properly.

[Ilya Sherman, 2013/05/02 06:34:09]

If you're only exposing it for testing, then I'd recommend moving it out of the
class into an "internal" namespace, with a comment indicating that it's exposed
just for testing.

[jrummell, 2013/05/02 21:53:09]

Moved to internal, test class is a friend.

+  { CONTAINER_4XM,          "4xm" },
+  { CONTAINER_AAC,          "aac" },
+  { CONTAINER_AC3,          "ac3" },
+  { CONTAINER_ACT,          "act" },
+  { CONTAINER_ADF,          "adf" },
+  { CONTAINER_ADX,          "adx" },
+  { CONTAINER_AEA,          "aea" },
+  { CONTAINER_AFC,          "afc" },
+  { CONTAINER_AIFF,         "aiff" },
+  { CONTAINER_ALAW,         "alaw" },
+  { CONTAINER_ALSA,         "alsa" },
+  { CONTAINER_AMR,          "amr" },
+  { CONTAINER_ANM,          "anm" },
+  { CONTAINER_APC,          "apc" },
+  { CONTAINER_APE,          "ape" },
+  { CONTAINER_AQTITLE,      "aqtitle" },
+  { CONTAINER_ASF,          "asf" },
+  { CONTAINER_ASS,          "ass" },
+  { CONTAINER_AST,          "ast" },
+  { CONTAINER_AU,           "au" },
+  { CONTAINER_AVI,          "avi" },
+  { CONTAINER_AVISYNTH,     "avisynth" },
+  { CONTAINER_AVR,          "avr" },
+  { CONTAINER_AVS,          "avs" },
+  { CONTAINER_BETHSOFTVID,  "bethsoftvid" },
+  { CONTAINER_BFI,          "bfi" },
+  { CONTAINER_BIN,          "bin" },
+  { CONTAINER_BINK,         "bink" },
+  { CONTAINER_BIT,          "bit" },
+  { CONTAINER_BKTR,         "bktr" },
+  { CONTAINER_BMV,          "bmv" },
+  { CONTAINER_BRSTM,        "brstm" },
+  { CONTAINER_C93,          "c93" },
+  { CONTAINER_CAF,          "caf" },
+  { CONTAINER_CAVSVIDEO,    "cavsvideo" },
+  { CONTAINER_CDG,          "cdg" },
+  { CONTAINER_CDXL,         "cdxl" },
+  { CONTAINER_CONCAT,       "concat" },
+  { CONTAINER_DAUD,         "daud" },
+  { CONTAINER_DFA,          "dfa" },
+  { CONTAINER_DIRAC,        "dirac" },
+  { CONTAINER_DNXHD,        "dnxhd" },
+  { CONTAINER_DSHOW,        "dshow" },
+  { CONTAINER_DSICIN,       "dsicin" },
+  { CONTAINER_DTS,          "dts" },
+  { CONTAINER_DTSHD,        "dtshd" },
+  { CONTAINER_DV,           "dv" },
+  { CONTAINER_DV1394,       "dv1394" },
+  { CONTAINER_DXA,          "dxa" },
+  { CONTAINER_EA,           "ea" },
+  { CONTAINER_EA_CDATA,     "ea_cdata" },
+  { CONTAINER_EAC3,         "eac3" },
+  { CONTAINER_EPAF,         "epaf" },
+  { CONTAINER_F32BE,        "f32be" },
+  { CONTAINER_F32LE,        "f32le" },
+  { CONTAINER_F64BE,        "f64be" },
+  { CONTAINER_F64LE,        "f64le" },
+  { CONTAINER_FBDEV,        "fbdev" },
+  { CONTAINER_FFM,          "ffm" },
+  { CONTAINER_FFMETADATA,   "ffmetadata" },
+  { CONTAINER_FILM_CPK,     "film_cpk" },
+  { CONTAINER_FILMSTRIP,    "filmstrip" },
+  { CONTAINER_FLAC,         "flac" },
+  { CONTAINER_FLIC,         "flic" },
+  { CONTAINER_FLV,          "flv" },
+  { CONTAINER_FRM,          "frm" },
+  { CONTAINER_G722,         "g722" },
+  { CONTAINER_G723_1,       "g723_1" },
+  { CONTAINER_G729,         "g729" },
+  { CONTAINER_GIF,          "gif" },
+  { CONTAINER_GSM,          "gsm" },
+  { CONTAINER_GXF,          "gxf" },
+  { CONTAINER_H261,         "h261" },
+  { CONTAINER_H263,         "h263" },
+  { CONTAINER_H264,         "h264" },
+  { CONTAINER_HLS,          "hls,applehttp" },
+  { CONTAINER_ICO,          "ico" },
+  { CONTAINER_IDCIN,        "idcin" },
+  { CONTAINER_IDF,          "idf" },
+  { CONTAINER_IEC61883,     "iec61883" },
+  { CONTAINER_IFF,          "iff" },
+  { CONTAINER_ILBC,         "ilbc" },
+  { CONTAINER_IMAGE2,       "image2" },
+  { CONTAINER_IMAGE2PIPE,   "image2pipe" },
+  { CONTAINER_INGENIENT,    "ingenient" },
+  { CONTAINER_IPMOVIE,      "ipmovie" },
+  { CONTAINER_IRCAM,        "ircam" },
+  { CONTAINER_ISS,          "iss" },
+  { CONTAINER_IV8,          "iv8" },
+  { CONTAINER_IVF,          "ivf" },
+  { CONTAINER_JACK,         "jack" },
+  { CONTAINER_JACOSUB,      "jacosub" },
+  { CONTAINER_JV,           "jv" },
+  { CONTAINER_LATM,         "latm" },
+  { CONTAINER_LAVFI,        "lavfi" },
+  { CONTAINER_LIBCDIO,      "libcdio" },
+  { CONTAINER_LIBDC1394,    "libdc1394" },
+  { CONTAINER_LIBMODPLUG,   "libmodplug" },
+  { CONTAINER_LIBNUT,       "libnut" },
+  { CONTAINER_LMLM4,        "lmlm4" },
+  { CONTAINER_LOAS,         "loas" },
+  { CONTAINER_LVF,          "lvf" },
+  { CONTAINER_LXF,          "lxf" },
+  { CONTAINER_M4V,          "m4v" },
+  { CONTAINER_WEBM,         "matroska,webm" },
+  { CONTAINER_MGSTS,        "mgsts" },
+  { CONTAINER_MICRODVD,     "microdvd" },
+  { CONTAINER_MJPEG,        "mjpeg" },
+  { CONTAINER_MLP,          "mlp" },
+  { CONTAINER_MM,           "mm" },
+  { CONTAINER_MMF,          "mmf" },
+  { CONTAINER_MOV,          "mov,mp4,m4a,3gp,3g2,mj2" },
+  { CONTAINER_MP3,          "mp3" },
+  { CONTAINER_MPC,          "mpc" },
+  { CONTAINER_MPC8,         "mpc8" },
+  { CONTAINER_MPEG,         "mpeg" },
+  { CONTAINER_MPEGTS,       "mpegts" },
+  { CONTAINER_MPEGTSRAW,    "mpegtsraw" },
+  { CONTAINER_MPEGVIDEO,    "mpegvideo" },
+  { CONTAINER_MPL2,         "mpl2" },
+  { CONTAINER_MPSUB,        "mpsub" },
+  { CONTAINER_MSNWCTCP,     "msnwctcp" },
+  { CONTAINER_MTV,          "mtv" },
+  { CONTAINER_MULAW,        "mulaw" },
+  { CONTAINER_MV,           "mv" },
+  { CONTAINER_MVI,          "mvi" },
+  { CONTAINER_MXF,          "mxf" },
+  { CONTAINER_MXG,          "mxg" },
+  { CONTAINER_NC,           "nc" },
+  { CONTAINER_NISTSPHERE,   "nistsphere" },
+  { CONTAINER_NSV,          "nsv" },
+  { CONTAINER_NUT,          "nut" },
+  { CONTAINER_NUV,          "nuv" },
+  { CONTAINER_OGG,          "ogg" },
+  { CONTAINER_OMA,          "oma" },
+  { CONTAINER_OPENAL,       "openal" },
+  { CONTAINER_OSS,          "oss" },
+  { CONTAINER_PAF,          "paf" },
+  { CONTAINER_PJS,          "pjs" },
+  { CONTAINER_PMP,          "pmp" },
+  { CONTAINER_PSXSTR,       "psxstr" },
+  { CONTAINER_PULSE,        "pulse" },
+  { CONTAINER_PVA,          "pva" },
+  { CONTAINER_PVF,          "pvf" },
+  { CONTAINER_QCP,          "qcp" },
+  { CONTAINER_R3D,          "r3d" },
+  { CONTAINER_RAWVIDEO,     "rawvideo" },
+  { CONTAINER_RDT,          "rdt" },
+  { CONTAINER_REALTEXT,     "realtext" },
+  { CONTAINER_RL2,          "rl2" },
+  { CONTAINER_RM,           "rm" },
+  { CONTAINER_ROQ,          "roq" },
+  { CONTAINER_RPL,          "rpl" },
+  { CONTAINER_RSO,          "rso" },
+  { CONTAINER_RTP,          "rtp" },
+  { CONTAINER_RTSP,         "rtsp" },
+  { CONTAINER_S16BE,        "s16be" },
+  { CONTAINER_S16LE,        "s16le" },
+  { CONTAINER_S24BE,        "s24be" },
+  { CONTAINER_S24LE,        "s24le" },
+  { CONTAINER_S32BE,        "s32be" },
+  { CONTAINER_S32LE,        "s32le" },
+  { CONTAINER_S8,           "s8" },
+  { CONTAINER_SAMI,         "sami" },
+  { CONTAINER_SAP,          "sap" },
+  { CONTAINER_SBG,          "sbg" },
+  { CONTAINER_SDP,          "sdp" },
+  { CONTAINER_SHN,          "shn" },
+  { CONTAINER_SIFF,         "siff" },
+  { CONTAINER_SMJPEG,       "smjpeg" },
+  { CONTAINER_SMK,          "smk" },
+  { CONTAINER_SMUSH,        "smush" },
+  { CONTAINER_SNDIO,        "sndio" },
+  { CONTAINER_SOL,          "sol" },
+  { CONTAINER_SOX,          "sox" },
+  { CONTAINER_SPDIF,        "spdif" },
+  { CONTAINER_SRT,          "srt" },
+  { CONTAINER_SUBVIEWER,    "subviewer" },
+  { CONTAINER_SUBVIEWER1,   "subviewer1" },
+  { CONTAINER_SWF,          "swf" },
+  { CONTAINER_TAK,          "tak" },
+  { CONTAINER_TEDCAPTIONS,  "tedcaptions" },
+  { CONTAINER_THP,          "thp" },
+  { CONTAINER_TIERTEXSEQ,   "tiertexseq" },
+  { CONTAINER_TMV,          "tmv" },
+  { CONTAINER_TRUEHD,       "truehd" },
+  { CONTAINER_TTA,          "tta" },
+  { CONTAINER_TTY,          "tty" },
+  { CONTAINER_TXD,          "txd" },
+  { CONTAINER_VC1,          "vc1" },
+  { CONTAINER_VC1TEST,      "vc1test" },
+  { CONTAINER_VFWCAP,       "vfwcap" },
+  { CONTAINER_V4L,          "video4linux,v4l" },
+  { CONTAINER_V4L2,         "video4linux2,v4l2" },
+  { CONTAINER_VIVO,         "vivo" },
+  { CONTAINER_VMD,          "vmd" },
+  { CONTAINER_VOBSUB,       "vobsub" },
+  { CONTAINER_VOC,          "voc" },
+  { CONTAINER_VPLAYER,      "vplayer" },
+  { CONTAINER_VQF,          "vqf" },
+  { CONTAINER_W64,          "w64" },
+  { CONTAINER_WAV,          "wav" },
+  { CONTAINER_WC3MOVIE,     "wc3movie" },
+  { CONTAINER_WEBVTT,       "webvtt" },
+  { CONTAINER_WSAUD,        "wsaud" },
+  { CONTAINER_WSVQA,        "wsvqa" },
+  { CONTAINER_WTV,          "wtv" },
+  { CONTAINER_WV,           "wv" },
+  { CONTAINER_X11GRAB,      "x11grab" },
+  { CONTAINER_XA,           "xa" },
+  { CONTAINER_XBIN,         "xbin" },
+  { CONTAINER_XMV,          "xmv" },
+  { CONTAINER_XWMA,         "xwma" },
+  { CONTAINER_YOP,          "yop" },
+  { CONTAINER_YUV4MPEGPIPE, "yuv4mpegpipe" }
+};
+
+// Lookup a container name using the list above (container_name_mapping)
+// to determine the container enum. If not found (recent addition to
+// FFmpeg or a name change), return CONTAINER_UNKNOWN.
+enum FFmpegContainerName ContainerNames::LookupContainer(
+    const char* container_name) {
+  DCHECK_NE(container_name, (const char*)NULL);

[Ilya Sherman, 2013/04/29 23:48:06]

nit: This is usually written as "DCHECK(container_name);"

[jrummell, 2013/04/30 21:36:50]

Done.

+
+  // Do a binary search through supported_mapping looking for a match.

[Ilya Sherman, 2013/04/29 23:48:06]

Any reason not to just use binary_search() from std::algorithm?

[jrummell, 2013/04/30 21:36:50]

My understanding of binary_search is that it simply returns true/false. I need
to get the appropriate CONTAINER value. I guess I could use lower_bound, but I
suspect it will be just as much code to get the array into a vector and write
comparison methods. There is a unit test that verifies calling this function
with each string returns the expected result.

[Ilya Sherman, 2013/05/02 06:34:09]

lower_bound should work with raw pointers into an array just as well as with a
vector.

[jrummell, 2013/05/02 21:53:09]

Done.

+  int left = 0;
+  int right = size(container_name_mapping) - 1;
+  while (left <= right) {
+    int middle = (left + right) / 2;
+    int compare = strcmp(container_name, container_name_mapping[middle].name);
+    if (compare == 0)
+      return container_name_mapping[middle].id;
+    else if (compare < 0)
+      right = middle - 1;
+    else
+      left = middle + 1;
+    }

[xhwang, 2013/04/29 21:00:25]

indent

[jrummell, 2013/04/30 21:36:50]

Done.

+  return CONTAINER_UNKNOWN;
+}
+
+// For some formats the signature is a bunch of characters. They are defined
+// below. If the string contains \00, then it needs to be handled differently.
+#define BOM                  "\xef\xbb\xbf"

[Ilya Sherman, 2013/04/29 23:48:06]

Any reason not to define this as a named constant, i.e. "const char
kByteOrderMark[] = "\xef\xbb\xbf";", rather than a macro?

[jrummell, 2013/04/30 21:36:50]

This is used in several definitions below, where it is prepended on a signature
to make an alternate signature.

+#define AMR_SIGNATURE        "#!AMR"
+#define AMR_TAG              TAG('#','!','A','M')
+
+#define APC_SIGNATURE        "CRYO_APC"
+#define APC_TAG              TAG('C','R','Y','O')
+
+#define AQTITLE_FORMAT       "-->> %d"
+#define AQTITLE_TAG          TAG('-','-','>','>')
+
+static const char ASF_SIGNATURE[] =
+    "\x30\x26\xb2\x75\x8e\x66\xcf\x11\xa6\xd9\x00\xaa\x00\x62\xce\x6c";
+#define ASF_TAG              0x3026b275
+
+#define ASS_SIGNATURE        "[Script Info]"
+#define ASS_TAG              TAG('[','S','c','r')
+#define ASS_BOM_SIGNATURE    BOM ASS_SIGNATURE
+#define ASS_BOM_TAG          TAG('\xef','\xbb','\xbf','[')
+
+#define CONCAT_SIGNATURE     "ffconcat version 1.0"
+#define CONCAT_TAG           TAG('f','f','c','o')
+
+static const char DNXHD_SIGNATURE[] = "\x00\x00\x02\x80\x01";
+#define DNXHD_TAG            0x00000280
+
+#define FFMETADATA_SIGNATURE ";FFMETADATA"
+#define FFMETADATA_TAG       TAG(';','F','F','M')
+
+#define HLS_SIGNATURE        "#EXTM3U"
+#define HLS_TAG              TAG('#','E','X','T')
+#define HLS1                 "#EXT-X-STREAM-INF:"
+#define HLS2                 "#EXT-X-TARGETDURATION:"
+#define HLS3                 "#EXT-X-MEDIA-SEQUENCE:"
+
+static const char IDF_SIGNATURE[] =

[Ilya Sherman, 2013/04/29 23:48:06]

nit: This should use kConstantName casing rather than MACRO_NAME casing.

[jrummell, 2013/04/30 21:36:50]

Done.

+    "\x04\x31\x2e\x34\x00\x00\x00\x00\x4f\x00\x15\x00";
+#define IDF_TAG              0x04312e34
+
+#define ILBC_SIGNATURE       "#!iLBC"
+#define ILBC_TAG             TAG('#','!','i','L')
+
+#define ISS_SIGNATURE        "IMA_ADPCM_Sound"
+#define ISS_TAG              TAG('I','M','A','_')
+
+#define IV8_SIGNATURE        "\x01\x01\x03\xb8\x80\x60"
+#define IV8_TAG              0x010103b8
+
+#define JV_SIGNATURE         " Compression by John M Phillips " \
+                             "Copyright (C) 1995 The Bitmap Brothers Ltd."
+
+#define LIBNUT_SIGNATURE     "nut/multimedia container"
+#define LIBNUT_TAG           TAG('n','u','t','/')
+
+static const char LXF_SIGNATURE[] = "LEITCH\x00\x00";
+#define LXF_TAG              TAG('L','E','I','T')
+
+#define NUV1_SIGNATURE       "NuppelVideo"
+#define NUV1_TAG             TAG('N','u','p','p')
+#define NUV2_SIGNATURE       "MythTVVideo"
+#define NUV2_TAG             TAG('M','y','t','h')
+
+#define PAF_SIGNATURE \
+  "Packed Animation File V1.0\n(c) 1992-96 Amazing Studio\x0a\x1a"
+#define PAF_TAG              TAG('P','a','c','k')
+
+#define REALTEXT_SIGNATURE        "<window"
+#define REALTEXT_TAG              TAG('<','w','i','n')
+#define REALTEXT_BOM_SIGNATURE    BOM REALTEXT_SIGNATURE
+#define REALTEXT_BOM_TAG          TAG('\xef','\xbb','\xbf','<')
+
+#define RPL_SIGNATURE        "ARMovie\x0A"
+#define RPL_TAG              TAG('A','R','M','o')
+
+#define SAMI_SIGNATURE       "<SAMI>"
+#define SAMI_TAG             TAG('<','S','A','M')
+#define SAMI_BOM_SIGNATURE   BOM SAMI_SIGNATURE
+#define SAMI_BOM_TAG         TAG('\xef','\xbb','\xbf','<')
+
+static const char SMJPEG_SIGNATURE[] = "\x00\x0aSMJPEG";
+#define SMJPEG_TAG           TAG('\x00','\x0a','S','M')
+
+#define VIVO_SIGNATURE       "\r\nVersion:Vivo/"
+
+#define VOBSUB_SIGNATURE     "# VobSub index file,"
+#define VOBSUB_TAG           TAG('#',' ','V','o')
+
+#define VOC_SIGNATURE        "Creative Voice File\x1A"
+#define VOC_TAG              TAG('C','r','e','a')
+
+static const char W64_SIGNATURE[] =
+    "riff\x2e\x91\xcf\x11\xa5\xd6\x28\xdb\x04\xc1\x00\x00";
+static const char W64_SIGNATURE2[] =
+    "wave\xf3\xac\xd3\x11\x8c\xd1\x00\xc0\x4f\x8e\xdb\x8a";
+
+#define WEBVTT_SIGNATURE     "WEBVTT"
+#define WEBVTT_TAG           TAG('W','E','B','V')
+#define WEBVTT_BOM_SIGNATURE BOM WEBVTT_SIGNATURE
+#define WEBVTT_BOM_TAG       TAG('\xef','\xbb','\xbf','W')
+
+static const char WTV_SIGNATURE[] =
+    "\xb7\xd8\x00\x20\x37\x49\xda\x11\xa6\x4e\x00\x07\xe9\x5e\xad\x8d";
+#define WTV_TAG              0xb7d80020
+
+#define YUV4_SIGNATURE       "YUV4MPEG2"
+#define YUV4_TAG             TAG('Y','U','V','4')
+
+const uint16_t ac3_frame_size_table[38][3] = {
+  { 128, 138, 192 }, { 128, 140, 192 }, { 160, 174, 240 }, { 160, 176, 240 },
+  { 192, 208, 288 }, { 192, 210, 288 }, { 224, 242, 336 }, { 224, 244, 336 },
+  { 256, 278, 384 }, { 256, 280, 384 }, { 320, 348, 480 }, { 320, 350, 480 },
+  { 384, 416, 576 }, { 384, 418, 576 }, { 448, 486, 672 }, { 448, 488, 672 },
+  { 512, 556, 768 }, { 512, 558, 768 }, { 640, 696, 960 }, { 640, 698, 960 },
+  { 768, 834, 1152 }, { 768, 836, 1152 }, { 896, 974, 1344 },
+  { 896, 976, 1344 }, { 1024, 1114, 1536 }, { 1024, 1116, 1536 },
+  { 1280, 1392, 1920 }, { 1280, 1394, 1920 }, { 1536, 1670, 2304 },
+  { 1536, 1672, 2304 }, { 1792, 1950, 2688 }, { 1792, 1952, 2688 },
+  { 2048, 2228, 3072 }, { 2048, 2230, 3072 }, { 2304, 2506, 3456 },
+  { 2304, 2508, 3456 }, { 2560, 2768, 3840 }, { 2560, 2770, 3840 },
+};
+
+// Additional checks for an AC3 container.
+bool check_ac3(const uint8_t buffer[], size_t buffer_size) {
+  // AC3 container looks like syncinfo | bsi | audblk * 6 | aux | check.
+  // from spec @ http://www.atsc.org/cms/standards/A52-2012(12-17).pdf
+  size_t offset = 0;
+
+  while (offset + 6 < buffer_size) {
+    // Verify syncinfo (5 bytes)
+    if (READ16(buffer + offset) != 0x0b77)
+      return false;
+    int sample_rate_code = (buffer[offset + 4] >> 6) & 0x03;
+    if (sample_rate_code == 3)  // reserved
+      return false;
+    int frame_size_code = buffer[offset + 4] & 0x3f;
+    if (frame_size_code >= 38)
+      return false;
+
+    // Verify bsi (no fixed alignment)
+    int bit_stream_id = (buffer[offset + 5] >> 3) & 0x1f;
+    if (bit_stream_id >= 10)  // normally 8 or 6
+      return false;
+
+    offset += ac3_frame_size_table[frame_size_code][sample_rate_code];
+  }
+  return true;
+}
+
+// Additional checks for an EAC3 container (very similar to AC3)
+bool check_eac3(const uint8_t buffer[], size_t buffer_size) {
+  // EAC3 container looks like syncinfo | bsi | audfrm | audblk* | aux | check.
+  // from spec @ http://www.atsc.org/cms/standards/A52-2012(12-17).pdf
+  size_t offset = 0;
+
+  while (offset + 6 < buffer_size) {
+    // Verify syncinfo (5 bytes)
+    if (READ16(buffer + offset) != 0x0b77)
+      return false;
+
+    // Verify bsi (no fixed alignment)
+    int stream_type = (buffer[offset + 2] > 6) & 0x3;
+    if (stream_type == 3)
+      return false;
+    int frame_size = ((READ16(buffer + offset + 2) & 0x7ff) + 1) * 2;
+    if (frame_size < 7)
+      return false;
+    int bit_stream_id = (buffer[offset + 5] >> 3) & 0x1f;
+    if (bit_stream_id != 16)
+      return false;
+
+    offset += frame_size;
+  }
+  return true;
+}
+
+// Additional checks for an ACT container.
+bool check_act(const uint8_t buffer[], size_t buffer_size) {
+  if (buffer_size < 512 || READ32(buffer + 16) != 16)
+    return false;
+  // Most of the first 512 bytes should be 0.
+  for (int i = 44; i < 256; ++i)
+    if (buffer[i] != 0)
+      return false;
+  if (buffer[256] != 0x84)
+    return false;
+  for (int i = 264; i < 512; ++i)
+    if (buffer[i] != 0)
+      return false;
+  return true;
+}
+
+// Additional checks for an AEA container.
+bool check_aea(const uint8_t buffer[], size_t buffer_size) {
+  if (buffer_size < 2260)
+    return false;
+  int channels = buffer[264];
+  return ((channels == 1 || channels == 2) &&
+          buffer[2048] == buffer[2259] &&
+          buffer[2049] == buffer[2258]);
+}
+
+// Additional checks for a BINK container.
+bool check_bink(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t frames = READ32(buffer + 8);
+  uint32_t width = READ32(buffer + 20);
+  uint32_t height = READ32(buffer + 24);
+  uint32_t fps = READ32(buffer + 28);
+  uint32_t den = READ32(buffer + 32);
+  return (frames > 0 && fps > 0 && den > 0 &&
+          (width > 0 && width <= 7680) &&
+          (height > 0 && height <= 4800));
+}
+
+// Additional checks for a C93 container.
+bool check_c93(const uint8_t buffer[], size_t buffer_size) {
+  int index = 1;
+  for (int i = 0; i < 16; i += 4) {
+    if (READ16(buffer + i) != index || !buffer[i + 2] || !buffer[i + 3])
+      return false;
+    index += buffer[i + 2];
+    }
+  return true;
+}
+
+// Additional checks for a CDXL container.
+bool check_cdxl(const uint8_t buffer[], size_t buffer_size) {
+  uint8_t type = buffer[0];
+  uint32_t current_size = READ32(buffer + 2);
+  uint32_t width = READ16(buffer + 14);
+  uint32_t height = READ16(buffer + 16);
+  uint8_t plane1 = buffer[18];
+  uint8_t plane2 = buffer[19];
+  uint32_t palette_size = READ16(buffer + 20);
+  uint32_t audio_size = READ16(buffer + 22);
+  uint32_t image_size = width * height * plane2 / 8;
+  return (type == 1 &&
+          palette_size <= 512 &&
+          plane1 != 0 &&
+          plane2 != 0 &&
+          width != 0 &&
+          height != 0 &&
+          current_size >= audio_size + palette_size + image_size + 32 &&
+          READ32(buffer + 24) == 0 &&
+          READ32(buffer + 28) == 0 &&
+          READ16(buffer + 10) == 0);
+}
+
+// Additional checks for a DNXHD container.
+bool check_dnxhd(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t height = READ16(buffer + 24);
+  uint32_t width = READ16(buffer + 26);
+  uint32_t compression = READ16(buffer + 40);
+  return (memcmp(buffer, DNXHD_SIGNATURE, sizeof(DNXHD_SIGNATURE)-1) == 0 &&
+          height > 0 &&
+          width > 0 &&
+          compression >= 1235 && compression <= 1253);
+}
+
+// Additional checks for a DSICIN container.
+bool check_dsicin(const uint8_t buffer[], size_t buffer_size) {
+  return (READ32(buffer + 12) == 22050 &&
+          buffer[16] == 16 &&
+          buffer[17] == 0);
+}
+
+// Additional checks for an IDCIN container.
+bool check_idcin(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t width = READ32(buffer);
+  uint32_t height = READ32(buffer + 4);
+  uint32_t rate = READ32(buffer + 8);
+  uint32_t bytes = READ32(buffer + 12);
+  uint32_t channels = READ32(buffer + 16);
+  return (width > 0 && width <= 1024 &&
+          height > 0 && height <= 1024 &&
+          rate >= 8000 && rate <= 48000 &&
+          bytes <= 2 &&
+          channels <= 2);
+}
+
+// Additional checks for a HLS container.
+bool check_hls(const uint8_t buffer[], size_t buffer_size) {
+  if (memcmp(buffer, HLS_SIGNATURE, strlen(HLS_SIGNATURE)) == 0) {
+    // Need to find "#EXT-X-STREAM-INF:", "#EXT-X-TARGETDURATION:",
+    // or "#EXT-X-MEDIA-SEQUENCE:" somewhere in the buffer
+    size_t offset = strlen(HLS_SIGNATURE);
+    while (offset < buffer_size - strlen(HLS2)) {
+      if (buffer[offset] == '#') {
+        if (memcmp(buffer + offset, HLS1, strlen(HLS1)) == 0 ||
+            memcmp(buffer + offset, HLS2, strlen(HLS2)) == 0 ||
+            memcmp(buffer + offset, HLS3, strlen(HLS3)) == 0)
+          return true;
+      }
+      ++offset;
+    }
+  }
+  return false;
+}
+
+// Additional checks for a MM container.
+bool check_mm(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t length = READ32(buffer + 2);
+  uint32_t fps = READ16(buffer + 8);
+  uint32_t width = READ16(buffer + 12);
+  uint32_t height = READ16(buffer + 14);
+  uint32_t type = READ16(buffer + length);
+  return ((length == 22 || length == 24) &&
+          fps > 0 && fps <= 60 &&
+          width > 0 && width <= 2048 &&
+          height > 0 && height <= 2048 &&
+          type > 0 && type < 50);
+}
+
+// Additional checks for a MOV container.
+bool check_mov(const uint8_t buffer[], size_t buffer_size) {
+  size_t offset = 0;
+  while (offset + 16 < buffer_size) {
+    uint32_t atomsize = READ32(buffer + offset);
+    uint32_t atomtype = READ32(buffer + offset + 4);
+    // Valid atoms from http://www.mp4ra.org/atoms.html
+    switch (atomtype) {
+      case TAG('a','i','n','f'):
+      case TAG('a','v','c','n'):
+      case TAG('b','l','o','c'):
+      case TAG('b','p','c','c'):
+      case TAG('b','u','f','f'):
+      case TAG('b','x','m','l'):
+      case TAG('c','c','i','d'):
+      case TAG('c','d','e','f'):
+      case TAG('c','m','a','p'):
+      case TAG('c','o','6','4'):
+      case TAG('c','o','l','r'):
+      case TAG('c','r','h','d'):
+      case TAG('c','s','l','g'):
+      case TAG('c','t','t','s'):
+      case TAG('c','v','r','u'):
+      case TAG('d','i','n','f'):
+      case TAG('d','r','e','f'):
+      case TAG('d','s','g','d'):
+      case TAG('d','s','t','g'):
+      case TAG('e','d','t','s'):
+      case TAG('e','l','s','t'):
+      case TAG('f','e','c','i'):
+      case TAG('f','e','c','r'):
+      case TAG('f','i','i','n'):
+      case TAG('f','i','r','e'):
+      case TAG('f','p','a','r'):
+      case TAG('f','r','e','e'):
+      case TAG('f','r','m','a'):
+      case TAG('f','t','y','p'):
+      case TAG('g','i','t','n'):
+      case TAG('g','r','p','i'):
+      case TAG('h','d','l','r'):
+      case TAG('h','m','h','d'):
+      case TAG('h','p','i','x'):
+      case TAG('i','c','n','u'):
+      case TAG('I','D','3','2'):
+      case TAG('i','d','a','t'):
+      case TAG('i','h','d','r'):
+      case TAG('i','i','n','f'):
+      case TAG('i','l','o','c'):
+      case TAG('i','m','i','f'):
+      case TAG('i','n','f','u'):
+      case TAG('i','o','d','s'):
+      case TAG('i','p','h','d'):
+      case TAG('i','p','m','c'):
+      case TAG('i','p','r','o'):
+      case TAG('i','r','e','f'):
+      case TAG('j','P',' ',' '):
+      case TAG('j','p','2','c'):
+      case TAG('j','p','2','h'):
+      case TAG('j','p','2','i'):
+      case TAG('l','r','c','u'):
+      case TAG('m','7','h','d'):
+      case TAG('m','d','a','t'):
+      case TAG('m','d','h','d'):
+      case TAG('m','d','i','a'):
+      case TAG('m','d','r','i'):
+      case TAG('m','e','c','o'):
+      case TAG('m','e','h','d'):
+      case TAG('m','e','r','e'):
+      case TAG('m','e','t','a'):
+      case TAG('m','f','h','d'):
+      case TAG('m','f','r','a'):
+      case TAG('m','f','r','o'):
+      case TAG('m','i','n','f'):
+      case TAG('m','j','h','d'):
+      case TAG('m','o','o','f'):
+      case TAG('m','o','o','v'):
+      case TAG('m','v','c','g'):
+      case TAG('m','v','c','i'):
+      case TAG('m','v','e','x'):
+      case TAG('m','v','h','d'):
+      case TAG('m','v','r','a'):
+      case TAG('n','m','h','d'):
+      case TAG('o','c','h','d'):
+      case TAG('o','d','a','f'):
+      case TAG('o','d','d','a'):
+      case TAG('o','d','h','d'):
+      case TAG('o','d','h','e'):
+      case TAG('o','d','r','b'):
+      case TAG('o','d','r','m'):
+      case TAG('o','d','t','t'):
+      case TAG('o','h','d','r'):
+      case TAG('p','a','d','b'):
+      case TAG('p','a','e','n'):
+      case TAG('p','c','l','r'):
+      case TAG('p','d','i','n'):
+      case TAG('p','i','t','m'):
+      case TAG('r','e','s',' '):
+      case TAG('r','e','s','c'):
+      case TAG('r','e','s','d'):
+      case TAG('s','b','g','p'):
+      case TAG('s','c','h','i'):
+      case TAG('s','c','h','m'):
+      case TAG('s','d','e','p'):
+      case TAG('s','d','h','d'):
+      case TAG('s','d','t','p'):
+      case TAG('s','d','v','p'):
+      case TAG('s','e','g','r'):
+      case TAG('s','e','n','c'):
+      case TAG('s','g','p','d'):
+      case TAG('s','i','d','x'):
+      case TAG('s','i','n','f'):
+      case TAG('s','k','i','p'):
+      case TAG('s','m','h','d'):
+      case TAG('s','r','m','b'):
+      case TAG('s','r','m','c'):
+      case TAG('s','r','p','p'):
+      case TAG('s','t','b','l'):
+      case TAG('s','t','c','o'):
+      case TAG('s','t','d','p'):
+      case TAG('s','t','h','d'):
+      case TAG('s','t','s','c'):
+      case TAG('s','t','s','d'):
+      case TAG('s','t','s','h'):
+      case TAG('s','t','s','s'):
+      case TAG('s','t','s','z'):
+      case TAG('s','t','t','s'):
+      case TAG('s','t','y','p'):
+      case TAG('s','t','z','2'):
+      case TAG('s','u','b','s'):
+      case TAG('s','w','t','c'):
+      case TAG('t','f','a','d'):
+      case TAG('t','f','h','d'):
+      case TAG('t','f','m','a'):
+      case TAG('t','f','r','a'):
+      case TAG('t','i','b','r'):
+      case TAG('t','i','r','i'):
+      case TAG('t','k','h','d'):
+      case TAG('t','r','a','f'):
+      case TAG('t','r','a','k'):
+      case TAG('t','r','e','f'):
+      case TAG('t','r','e','x'):
+      case TAG('t','r','g','r'):
+      case TAG('t','r','i','k'):
+      case TAG('t','r','u','n'):
+      case TAG('u','d','t','a'):
+      case TAG('u','i','n','f'):
+      case TAG('U','I','T','S'):
+      case TAG('u','l','s','t'):
+      case TAG('u','r','l',' '):
+      case TAG('u','u','i','d'):
+      case TAG('v','m','h','d'):
+      case TAG('v','w','d','i'):
+      case TAG('x','m','l',' '):
+      case TAG('C','o','d','e'):
+      case TAG('a','l','b','m'):
+      case TAG('a','n','g','l'):
+      case TAG('a','u','t','h'):
+      case TAG('c','l','f','n'):
+      case TAG('c','l','i','d'):
+      case TAG('c','l','s','f'):
+      case TAG('c','m','i','d'):
+      case TAG('c','m','n','m'):
+      case TAG('c','o','l','l'):
+      case TAG('c','p','r','t'):
+      case TAG('d','a','t','e'):
+      case TAG('d','s','c','p'):
+      case TAG('g','n','r','e'):
+      case TAG('h','n','t','i'):
+      case TAG('k','y','w','d'):
+      case TAG('l','o','c','i'):
+      case TAG('m','a','n','u'):
+      case TAG('m','o','d','l'):
+      case TAG('p','e','r','f'):
+      case TAG('r','e','e','l'):
+      case TAG('r','t','n','g'):
+      case TAG('s','c','e','n'):
+      case TAG('s','h','o','t'):
+      case TAG('s','l','n','o'):
+      case TAG('s','t','r','k'):
+      case TAG('t','h','m','b'):
+      case TAG('t','s','e','l'):
+      case TAG('t','i','t','l'):
+      case TAG('u','r','a','t'):
+      case TAG('y','r','r','c'):
+      case TAG('c','l','i','p'):
+      case TAG('c','r','g','n'):
+      case TAG('c','t','a','b'):
+      case TAG('d','c','f','D'):
+      case TAG('e','l','n','g'):
+      case TAG('i','m','a','p'):
+      case TAG('k','m','a','t'):
+      case TAG('l','o','a','d'):
+      case TAG('m','a','t','t'):
+      case TAG('p','n','o','t'):
+      case TAG('w','i','d','e'):
+        break;
+      default:
+        return false;
+    }
+    if (atomsize == 0)
+      break;  // indicates the last atom
+    if (atomsize == 1) {
+      // Indicates that the length is the next 64bits.
+      if (READ32(buffer + offset + 8) != 0)
+        break;  // offset is way past buffer size
+      atomsize = READ32(buffer + offset + 12);
+    }
+    offset += atomsize;
+  }
+  return true;
+}
+
+enum MPEGVersion {
+  Version25 = 0,
+  v_reserved,
+  Version2,
+  Version1
+};
+enum MPEGlayer {
+  l_reserved = 0,
+  Layer3,
+  Layer2,
+  Layer1
+};
+
+static int Sample_Rate_Table[4][4] = {
+  { 11025, 12000, 8000, 0 },  // v2.5
+  { 0, 0, 0, 0 },             // not used
+  { 22050, 24000, 16000, 0 }, // v2
+  { 44100, 48000, 32000, 0 }  // v1
+};
+
+static int Bit_Rate_Table_v1_l1[16] =
+  { 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0 };
+static int Bit_Rate_Table_v1_l2[16] =
+  { 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 };
+static int Bit_Rate_Table_v1_l3[16] =
+  { 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0 };
+static int Bit_Rate_Table_v2_l1[16] =
+  { 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 };
+static int Bit_Rate_Table_v2_l23[16] =
+  { 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 };
+
+bool valid_mpeg_audio_frame_header(uint32_t header, size_t *framesize) {
+  *framesize = 0;
+  // first 11 bits must be all set
+  if ((header & 0xffe00000) != 0xffe00000)
+    return false;
+  // version (bits 20-19) can not be 01
+  int version = (header >> 19) & 0x3;
+  if (version == 1)
+    return false;
+  // layer (bits 18-17) can not be 00
+  int layer = (header >> 17) & 0x3;
+  if (layer == 0)
+    return false;
+  // bitrate (bits 15-12) can not be 1111
+  int bitrate_index = (header >> 12) & 0xf;
+  if (bitrate_index == 0xf)
+    return false;
+  // sampling (bits 11-10) can not be 11
+  int sampling_index = (header >> 10) & 0x3;
+  if (sampling_index == 3)
+    return false;
+
+  // Frame size:
+  // For Layer I files = (12 * BitRate / SampleRate + Padding) * 4
+  // For others = 144 * BitRate / SampleRate + Padding
+  // Unfortunately, BitRate and SampleRate are coded
+  int padding = (header >> 9) & 0x1;
+  int sampling_rate = Sample_Rate_Table[version][sampling_index];
+  int bitrate;
+  if (version == Version1) {
+    if (layer == Layer1)
+      bitrate = Bit_Rate_Table_v1_l1[bitrate_index];
+    else if (layer == Layer2)
+      bitrate = Bit_Rate_Table_v1_l2[bitrate_index];
+    else
+      bitrate = Bit_Rate_Table_v1_l3[bitrate_index];
+  }
+  else {
+    if (layer == Layer1)
+      bitrate = Bit_Rate_Table_v2_l1[bitrate_index];
+    else
+      bitrate = Bit_Rate_Table_v2_l23[bitrate_index];
+  }
+  if (layer == Layer1)
+    *framesize = ((12000 * bitrate) / sampling_rate + padding) * 4;
+  else
+    *framesize = (144000 * bitrate) / sampling_rate + padding;
+  return (bitrate > 0 && sampling_rate > 0);
+}
+
+// Extract a size encoded the MP3 way
+uint32_t get_mp3_header_size(const uint8_t buffer[]) {
+  uint32_t size = ((buffer[6] & 0x7f) << 21) +
+                  ((buffer[7] & 0x7f) << 14) +
+                  ((buffer[8] & 0x7f) << 7) +
+                   (buffer[9] & 0x7f) +
+                    10;
+  if (buffer[5] & 0x10)  // footer added?
+    size += 10;
+  return size;
+}
+
+// Additional checks for a MP3 container.
+bool check_mp3(const uint8_t buffer[], size_t buffer_size, bool seenHeader) {
+  size_t framesize;
+  size_t numSeen = 0;
+  size_t offset = 0;
+  if (seenHeader)
+    offset = get_mp3_header_size(buffer);
+  while (offset + 3 <= buffer_size &&
+         valid_mpeg_audio_frame_header(READ32(buffer + offset), &framesize)) {
+    ++numSeen;
+    offset += framesize;
+  }
+  return (numSeen > 10 || offset >= buffer_size);
+}
+
+// Extract an encoded MPC size, returning the value and
+// the number of characters used by the size.
+int64_t get_mpc8_header_size(const uint8_t * b, size_t * count) {
+  int64_t size = 0;
+  uint8_t c;
+  *count = 0;
+  do {
+    c = *b++;
+    if (++(*count) > 10)
+      return -1;
+    size = (size << 7) | (c & 0x7f);
+  } while (c & 0x80);
+  return size;
+}
+
+// Additional checks for a MPC8 container.
+bool check_mpc8(const uint8_t buffer[], size_t buffer_size) {
+  size_t offset = 4;
+  while (offset < buffer_size - 14) {
+    if (!isupper(buffer[offset]) || !isupper(buffer[offset + 1]))
+      return false;
+
+    size_t size_characters;
+    int64_t size = get_mpc8_header_size(buffer + offset, &size_characters);
+    if (size < 2)
+      return false;
+    if (buffer[offset] == 'S' && buffer[offset + 1] == 'H') {
+      return (size >= 11 && size <= 28 &&
+              READ32(buffer + offset + size_characters + 2) != 0);
+    }
+    offset = offset + size + size_characters;
+  }
+  return false;
+}
+
+// Additional checks for a MSNWCTCP container.
+bool check_msnwctcp(const uint8_t buffer[], size_t buffer_size) {
+  // The FFmpeg probe scans through the complete buffer looking for
+  // a matching header. This code only looks for it at the beginning
+  // of the buffer.
+  uint32_t width = READ16(buffer + 2);
+  uint32_t height = READ16(buffer + 4);
+  if (!(width == 320 && height == 240) && !(width == 160 && height == 120))
+    return false;
+  return (READ32(buffer + 12) != TAG('M','L','2','0'));
+}
+
+// Additional checks for a MTV container.
+bool check_mtv(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t bpp = READ16(buffer + 50);
+  if (bpp != 16)
+    return false;
+  uint32_t width = READ16(buffer + 52);
+  uint32_t height = READ16(buffer + 54);
+  uint32_t segment_size = READ16(buffer + 56);
+  return ((width != 0 && height != 0) || (segment_size != 0));
+}
+
+// Additional checks for a NC container.
+bool check_nc(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t size = READ16(buffer + 5);
+  return (size + 20 < buffer_size && READ32(buffer + size + 16) == 0x1a5);
+}
+
+// Additional checks for a NSV container, only if the header isn't
+// at the start of the file.
+bool check_nsv(const uint8_t buffer[], size_t buffer_size) {
+  // Get the chunk size and check if at the end we are getting 0xBEEF
+  if (buffer_size < 24)
+    return false;
+  size_t vsize = READ24(buffer + 19) >> 4;
+  size_t asize = READ16(buffer + 22);
+  size_t offset = 24 + asize + vsize;
+  return (offset + 2 <= buffer_size && READ16(buffer + offset) == 0xbeef);
+}
+
+// Additional checks for an OMA container.
+bool check_oma(const uint8_t buffer[], size_t buffer_size) {
+  if (buffer[4] != 0)
+    return false;
+  uint32_t tag_len = get_mp3_header_size(buffer);
+  if (tag_len > buffer_size - 6)
+    return false;
+  return (READ24(buffer + tag_len) == TAG(0,'E','A','3') &&
+          buffer[tag_len + 4] == 0 && buffer[tag_len + 5] == 96);
+}
+
+// Additional checks for a PJS container.
+bool check_pjs(const uint8_t buffer[], size_t buffer_size) {
+  const char * ptr = reinterpret_cast<const char *>(buffer);
+  char c;
+  if (sscanf(ptr, "%*64d,%*64d,%c", &c) == 1) {
+    size_t offset = 0;
+    while (buffer[offset] != '"' && offset < buffer_size - 2)
+      ++offset;
+    ++offset;
+    while (buffer[offset] != '"' && offset < buffer_size) {
+      if (buffer[offset] == '\n' || buffer[offset] == '\r')
+        return false;
+      ++offset;
+    }
+    return true;
+  }
+  return false;
+}
+
+// Additional checks for a PVA container.
+bool check_pva(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t length = READ16(buffer + 6);
+  if (buffer[4] != 0x55 || (buffer[5] & 0xe0) != 0 || length > 6136)
+    return false;
+  if (buffer_size < length + 8)
+    return false;
+  return (buffer[length] == 'A' &&
+          buffer[length + 1] == 'V' &&
+          (buffer[length + 2] == 1 || buffer[length + 2] == 2) &&
+          buffer[length + 4] == 0x55 &&
+          (buffer[5] & 0xe0) == 0 &&
+          READ16(buffer + length + 6) <= 6136);
+}
+
+// Additional checks for a TIERTEXSEQ container.
+bool check_tiertexseq(const uint8_t buffer[], size_t buffer_size) {
+  // No real header, but first 256 bytes are always 0
+  if (buffer_size < 257)
+    return false;
+  for (int i = 0; i < 256; ++i)
+    if (buffer[i] != 0)
+      return false;
+  return (buffer[256] != 0 && buffer[257] != 0);
+}
+
+// Additional checks for a TMV container.
+bool check_tmv(const uint8_t buffer[], size_t buffer_size) {
+  return (READ16(buffer + 4) >= 5000 &&   // sample rate
+          READ16(buffer + 6) >= 41 &&     // audio size
+          buffer[8] == 0 &&               // compression method
+          buffer[9] != 0 &&               // width
+          buffer[10] != 0);               // height
+}
+
+// Additional checks for a VIVO container.
+bool check_vivo(const uint8_t buffer[], size_t buffer_size) {
+  if (buffer[0] != 0)
+    return false;
+  uint32_t length = buffer[1] & 0x7f;
+  size_t offset = 2;
+  if ((buffer[1] & 0x80) != 0) {
+    if (buffer[2] & 0x80)
+      return false;
+    length = (length << 7) + (buffer[2] & 0x7f);
+    offset = 3;
+  }
+  if (length < 21 || length > 1024)
+    return false;
+  return (memcmp(buffer + offset,
+                 VIVO_SIGNATURE,
+                 strlen(VIVO_SIGNATURE)) == 0 &&
+          buffer[offset + 16] >= '0' && buffer[offset + 16] <= '2');
+
+}
+
+// Additional checks for a VMD container.
+bool check_vmd(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t width = READ16(buffer + 12);
+  uint32_t height = READ16(buffer + 14);
+  return (width > 0 && width <= 2048 && height > 0 && height <= 2048);
+}
+
+// Additional checks for a VPLAYER container.
+bool check_vplayer(const uint8_t buffer[], size_t buffer_size) {
+  const char* ptr = reinterpret_cast<const char*>(buffer);
+  char c;
+  return (sscanf(ptr, "%*d:%*d:%*d.%*d%c", &c) == 1 && strchr(": =", c));
+}
+
+// Additional checks for a VQF container.
+bool check_vqf(const uint8_t buffer[], size_t buffer_size) {
+  const char* ptr = reinterpret_cast<const char*>(buffer + 4);
+  return (memcmp(ptr, "97012000", 8) == 0 || memcmp(ptr, "00052200", 8) == 0);
+}
+
+// Read a Matroska TAG, updating offset to point past it.
+int get_vtag(const uint8_t buffer[], size_t * offset) {
+  // Size of the tag is determined the same way as VINT,
+  // but the bit is not removed. Maximum of 4 bytes.
+  int result = buffer[*offset];
+  if ((result & 0x80) != 0) {
+    // It is a one byte tag
+    ++*offset;
+  }
+  else if ((result & 0x40) != 0) {
+    // It is a 2 byte tag
+    result = READ16(buffer + *offset);
+    *offset += 2;
+  }
+  else if ((result & 0x20) != 0) {
+    // It is a 3 byte tag
+    result = READ24(buffer + *offset);
+    *offset += 3;
+  }
+  else {
+    // It is a 4 byte tag
+    result = READ32(buffer + *offset);
+    *offset += 4;
+  }
+  return result;
+}
+
+// Read a Matroska VINT, updating offset to point past it.
+int get_vint(const uint8_t buffer[], size_t * offset) {
+  // Length = 1 + [number_of_leading_zero_bits].
+  int size = 1;
+  int mask = 0x80;
+  uint8_t b = buffer[*offset];
+  while (mask > 0 && (b & mask) == 0) {
+    ++size;
+    mask = mask >> 1;
+  }
+
+  // Now that we know the size, use the remaining bits plus
+  // following bytes to get the value.
+  int result = buffer[(*offset)++] & (mask - 1);
+  while (--size > 0)
+    result = (result << 8) | buffer[(*offset)++];
+  return result;
+}
+
+// Additional checks for a WEBM container.
+bool check_webm(const uint8_t buffer[], size_t buffer_size) {
+  size_t offset = 4;
+  int header_size = get_vint(buffer, &offset);
+  size_t lastoffset = offset + header_size;
+  if (lastoffset > buffer_size)
+    return false;
+  while (offset < lastoffset) {
+    int tag = get_vtag(buffer, &offset);
+    int tagsize = get_vint(buffer, &offset);
+    switch (tag) {
+      case 0x4286:  // EBMLVersion
+      case 0x42f7:  // EBMLReadVersion
+      case 0x42f2:  // EBMLMaxIdLength
+      case 0x42f3:  // EBMLMaxSizeLength
+      case 0x4287:  // DocTypeVersion
+      case 0x4285:  // DocTypeReadVersion
+      case 0xec:    // void
+      case 0xbf:    // CRC32
+        offset += tagsize;
+        break;
+      case 0x4282:  // EBMLDocType
+        return ((tagsize >= 4 && memcmp(buffer + offset, "webm", 4) == 0) ||
+                (tagsize >= 8 && memcmp(buffer + offset, "matroska", 8) == 0));
+      default:
+        // Unrecognized tag
+        return false;
+    }
+  }
+  return false;
+}
+
+// Additional checks for a WSAUD container.
+bool check_wsaud(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t sample_rate = READ16(buffer);
+  if (sample_rate < 8000 || sample_rate > 48000)
+    return false;
+  if ((buffer[10] & 0xfc) != 0 || (buffer[11] != 1 && buffer[11] != 99))
+    return false;
+  return (READ32(buffer + 16) == 0x0000deaf);
+}
+
+// Additional checks for a XA container.
+bool check_xa(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t channels = READ16(buffer + 10);
+  if (channels < 1 || channels > 8)
+    return false;
+  uint32_t srate = READ16(buffer + 12);
+  if (srate < 1 || srate > 192000)
+    return false;
+  uint32_t bits_per_sample = READ16(buffer + 10);
+  return (bits_per_sample >= 4 || bits_per_sample <= 32);
+}
+
+// Additional checks for a XBIN container.
+bool check_xbin(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t x = READ16(buffer + 5);
+  return (buffer[4] == 0x1a &&
+          x > 0 && x <= 160 &&
+          buffer[9] > 0 && buffer[9] <= 32);
+}
+
+// Additional checks for a XMV container.
+bool check_xmv(const uint8_t buffer[], size_t buffer_size) {
+  uint32_t version = READ16(buffer + 16);
+  return (READ32(buffer + 12) == TAG('x','o','b','X') &&
+          version > 0 && version <= 4);
+}
+
+// Additional checks for a YOP container.
+bool check_yop(const uint8_t buffer[], size_t buffer_size) {
+  return (buffer[2] < 10 &&
+          buffer[3] < 10 &&
+          buffer[6] != 0 &&
+          buffer[7] != 0 &&
+          (buffer[8] & 1) == 0 &&
+          (buffer[10] & 1) == 0 &&
+          READ16(buffer + 18) >= 920 &&
+          READ16(buffer + 18) < buffer[12] * 3 + 4 + buffer[7] * 2048);
+}
+
+// Attempt to determine the container type from the buffer provided. This is
+// a simple pass, that uses the first 4 bytes of the buffer as an index to get
+// a rough idea of the container format. It covers the following containers
+// (those with * are not fully covered):
+//   4xm, act, aea, aiff, amr, anm, apc, ape, aqtitle, asf, ass, ast, au, avi,
+//   avr, avs, bethsoftvid, bfi, bink, bit, brstm, c93, caff, cdxl, concat,
+//   dfa, dnxhd, dsicin, dtshd, dxa, ea, epaf, ffm, ffmetadata, file_cpk, flac,
+//   flic, flv, frm, gif, gxf, hls, ico, idf, iff, ilbc, ircam, iss, iv8, ivf,
+//   jv, libnut, lmlm4, lvf, lxf, mgsts, mm, mmf, mov, mp3*, mpc, mpc8,
+//   msnwctcp*, mtv, mv, nc, nistsphere, nsv*, nut, nuv, ogg, oma, paf, pmp,
+//   pva, pvf, qcp, r3d, realtext, rl2, rm, roq, rpl, sami, siff, smjpeg, smk,
+//   smush, sol, sox, swf, tak, thp, tiertexseq, tmv, tta, txd, vc1test, vivo,
+//   vmd, vobsub, voc, vqf, w64, wav, wc3movie, webm, webvtt, wsaud, wsvqa,
+//   wtv, wv, xa, xbin, xmv, xwma, yop, yuv4mpegpipe
+enum FFmpegContainerName LookupContainerByFirst4(const uint8 buffer[],
+    size_t buffer_size) {
+  // Minimum size that the code expects to exist without checking size.
+  // This includes the longest SIGNATURE checked.
+  if (buffer_size < 128)
+    return CONTAINER_UNKNOWN;
+
+  uint32_t first4 = READ32(buffer);
+  uint32_t second4 = READ32(buffer + 4);
+  uint32_t third4 = READ32(buffer + 8);
+  const char* ptr = reinterpret_cast<const char*>(buffer);
+  int frame;
+  uint32_t next;
+
+  switch (first4) {
+    case 0:
+      if (READ16(buffer + 4) == 0x1bc &&
+          READ32(buffer + 10) == 0 &&
+          READ16(buffer + 14) == 0xe1e2)
+        return CONTAINER_GXF;
+      if (check_mm(buffer, buffer_size))
+        return CONTAINER_MM;
+      if (second4 > 0 && second4 <= 1024 * 1024 && READ24(buffer + 8) == 1)
+        return CONTAINER_LMLM4;
+      if (check_tiertexseq(buffer, buffer_size))
+        return CONTAINER_TIERTEXSEQ;
+      break;
+    case 1:
+      if (second4 > 0 && second4 <= 1024 * 1024 && READ24(buffer + 8) == 1)
+        return CONTAINER_LMLM4;
+      if (READ16(buffer + 4) != 0)
+        return CONTAINER_ICO;
+      break;
+    case 2:
+      if (second4 > 0 && second4 <= 1024 * 1024 && READ24(buffer + 8) == 1)
+        return CONTAINER_LMLM4;
+      break;
+    case 4:
+      if (second4 > 0 && second4 <= 1024 * 1024 &&
+          (READ16(buffer + 8) & 0xfffe) == 0xfffc)
+        return CONTAINER_LMLM4;
+      break;
+    case 0xe:
+      if (second4 == 0x50 && READ32(buffer + 12) == 0x34)
+        return CONTAINER_MGSTS;
+      break;
+    case 0x16:
+      if (third4 == 0x1803ffff || third4 == 0x1003ffff)
+        return CONTAINER_TXD;
+      break;
+    case 0x1a5:
+      if (check_nc(buffer, buffer_size))
+        return CONTAINER_NC;
+      break;
+    case DNXHD_TAG: // TAG('\x00','\x00','\x02','\x80')
+      if (check_dnxhd(buffer, buffer_size))
+        return CONTAINER_DNXHD;
+      break;
+    case 0x800:
+      if (check_aea(buffer, buffer_size))
+        return CONTAINER_AEA;
+      break;
+    case 0x001800a0:
+    case 0x00180140:
+      if (check_msnwctcp(buffer, buffer_size))
+        return CONTAINER_MSNWCTCP;
+      break;
+    case SMJPEG_TAG: // TAG('\x00','\x0a','S','M')
+      if (memcmp(buffer, SMJPEG_SIGNATURE, sizeof(SMJPEG_SIGNATURE) - 1) == 0)
+        return CONTAINER_SMJPEG;
+    break;
+    case 0x1084ffff:
+      if (READ16(buffer + 4) == 0xffff)
+        return CONTAINER_ROQ;
+      break;
+    case IV8_TAG: // TAG('\x01','\x01','\x03','\xb8')
+      if (memcmp(buffer, IV8_SIGNATURE, strlen(IV8_SIGNATURE)) == 0)
+        return CONTAINER_IV8;
+      break;
+    case IDF_TAG: // TAG('\x04','\x31','\x2e','\x34')
+      if (memcmp(buffer, IDF_SIGNATURE, sizeof(IDF_SIGNATURE) - 1) == 0)
+        return CONTAINER_IDF;
+      break;
+    case TAG('\x0b','\x8d','S','O'):
+    case TAG('\x0c','\x0d','S','O'):
+    case TAG('\x0c','\x8d','S','O'):
+      if (buffer[4] == 'L' && buffer[5] == 0)
+        return CONTAINER_SOL;
+      break;
+    case 0x1a45dfa3:
+      if (check_webm(buffer, buffer_size))
+        return CONTAINER_WEBM;
+      break;
+    case TAG('.','s','n','d'):
+      return CONTAINER_AU;
+    case ASF_TAG: // TAG('\x30','\x26','\xB2','\x75')
+      if (memcmp(buffer, ASF_SIGNATURE, sizeof(ASF_SIGNATURE) - 1) == 0)
+        return CONTAINER_ASF;
+      break;
+    case TAG(' ','p','a','f'):
+      if (second4 == 0 && third4 == 0 &&
+          READ32(buffer + 12) != 0 &&
+          READ32(buffer + 20) != 0)
+        return CONTAINER_EPAF;
+      break;
+    case AMR_TAG: // TAG('#','!','A','M'):
+      if (memcmp(buffer, AMR_SIGNATURE, strlen(AMR_SIGNATURE)) == 0)
+        return CONTAINER_AMR;
+      break;
+    case ILBC_TAG: // TAG('#','!','i','L')
+      if (memcmp(buffer, ILBC_SIGNATURE, strlen(ILBC_SIGNATURE)) == 0)
+        return CONTAINER_ILBC;
+      break;
+    case HLS_TAG: // TAG('#','E','X','T')
+      if (check_hls(buffer, buffer_size))
+        return CONTAINER_HLS;
+      break;
+    case VOBSUB_TAG: // TAG('#',' ','V','o')
+      if (memcmp(buffer, VOBSUB_SIGNATURE, strlen(VOBSUB_SIGNATURE)) == 0)
+        return CONTAINER_VOBSUB;
+      break;
+    case AQTITLE_TAG: // TAG('-','-','>','>')
+      if (sscanf(ptr, AQTITLE_FORMAT, &frame) == 1)
+        return CONTAINER_AQTITLE;
+      break;
+    case TAG('.','R','M','F'):
+      if (buffer[4] == 0 && buffer[5] == 0)
+        return CONTAINER_RM;
+      break;
+    case TAG('.','r','a','\xfd'):
+      return CONTAINER_RM;
+    case TAG('.','S','o','X'):
+    case TAG('X','o','S','.'):
+      return CONTAINER_SOX;
+    case TAG('1','S','N','h'):
+    case TAG('S','C','H','l'):
+    case TAG('S','E','A','D'):
+    case TAG('S','H','E','N'):
+    case TAG('k','V','G','T'):
+    case TAG('M','A','D','k'):
+    case TAG('M','P','C','h'):
+    case TAG('M','V','h','d'):
+      if ((second4 > 0x0fffff) && ((second4 & 0x0f0ff) != 0))
+        return CONTAINER_EA;
+      break;
+    case TAG('2','B','I','T'):
+      return CONTAINER_AVR;
+    case TAG('A','N','I','M'):
+      if (third4 == TAG('A','H','D','R'))
+        return CONTAINER_SMUSH;
+      break;
+    case RPL_TAG: // TAG('A','R','M','o')
+      if (memcmp(buffer, RPL_SIGNATURE, strlen(RPL_SIGNATURE)) == 0)
+        return CONTAINER_RPL;
+      break;
+    case TAG('B','B','C','D'):
+      return CONTAINER_DIRAC;
+    case TAG('B','F','&','I'):
+      return CONTAINER_BFI;
+    case FFMETADATA_TAG: // TAG(';','F','F','M')
+      if (memcmp(buffer,
+                 FFMETADATA_SIGNATURE,
+                 strlen(FFMETADATA_SIGNATURE)) == 0)
+        return CONTAINER_FFMETADATA;
+      break;
+    case TAG('B','I','K','b'):
+    case TAG('B','I','K','f'):
+    case TAG('B','I','K','g'):
+    case TAG('B','I','K','h'):
+    case TAG('B','I','K','i'):
+      if (check_bink(buffer, buffer_size))
+        return CONTAINER_BINK;
+      break;
+    case TAG('c','a','f','f'):
+      if (READ16(buffer + 4) == 1)
+        return CONTAINER_CAF;
+      break;
+    case VOC_TAG: // TAG('C','r','e','a')
+      if (memcmp(buffer, VOC_SIGNATURE, strlen(VOC_SIGNATURE)) == 0)
+        return CONTAINER_VOC;
+      break;
+    case APC_TAG: // TAG('C','R','Y','O'):
+      if (memcmp(buffer, APC_SIGNATURE, strlen(APC_SIGNATURE)) == 0)
+        return CONTAINER_APC;
+      break;
+    case TAG('D','E','X','A'):
+      if (READ16(buffer + 11) <= 2048 && READ16(buffer + 13) <= 2048)
+        return CONTAINER_DXA;
+      break;
+    case TAG('D','K','I','F'):
+      if (second4 == 32)
+        return CONTAINER_IVF;
+      break;
+    case TAG('D','T','S','H'):
+      if (second4 == TAG('D','H','D','R'))
+        return CONTAINER_DTSHD;
+      break;
+    case TAG('D','F','I','A'):
+      return CONTAINER_DFA;
+    case TAG('\x64','\xa3','\x01','\x00'):
+    case TAG('\x64','\xa3','\x02','\x00'):
+    case TAG('\x64','\xa3','\x03','\x00'):
+    case TAG('\x64','\xa3','\x04','\x00'):
+    case TAG('\x00','\x01','\xa3','\x64'):
+    case TAG('\x00','\x02','\xa3','\x64'):
+    case TAG('\x00','\x03','\xa3','\x64'):
+      if (second4 != 0 && third4 != 0)
+        return CONTAINER_IRCAM;
+      break;
+    case TAG('e','a','3','\x03'):
+      if (check_oma(buffer, buffer_size))
+        return CONTAINER_OMA;
+      break;
+    case TAG('f','a','p',' '):
+      if (second4 == 0 && third4 == 1 &&
+          READ32(buffer + 12) != 0 &&
+          READ32(buffer + 20) != 0)
+        return CONTAINER_EPAF;
+      break;
+    case CONCAT_TAG: // TAG('f','f','c','o')
+      if (memcmp(buffer, CONCAT_SIGNATURE, strlen(CONCAT_SIGNATURE)) == 0)
+        return CONTAINER_CONCAT;
+      break;
+    case TAG('F','F','M','1'):
+    case TAG('F','F','M','2'):
+      return CONTAINER_FFM;
+    case TAG('F','I','L','M'):
+      return CONTAINER_FILM_CPK;
+    case TAG('f','L','a','C'):
+      return CONTAINER_FLAC;
+    case TAG('F','L','V','\x00'):
+    case TAG('F','L','V','\x01'):
+    case TAG('F','L','V','\x02'):
+    case TAG('F','L','V','\x03'):
+    case TAG('F','L','V','\x04'):
+      if (buffer[5] == 0 && READ32(buffer + 5) > 8)
+        return CONTAINER_FLV;
+      break;
+    case TAG('F','O','R','M'):
+      switch (third4) {
+        case TAG('A','I','F','F'):
+        case TAG('A','I','F','C'):
+          return CONTAINER_AIFF;
+        case TAG('8','S','V','X'):
+        case TAG('1','6','S','V'):
+        case TAG('M','A','U','D'):
+        case TAG('P','B','M',' '):
+        case TAG('A','C','B','M'):
+        case TAG('D','E','E','P'):
+        case TAG('I','L','B','M'):
+        case TAG('R','G','B','8'):
+        case TAG('R','G','B','N'):
+          return CONTAINER_IFF;
+        case TAG('M','O','V','E'):
+          return CONTAINER_WC3MOVIE;
+        case TAG('R','L','V','2'):
+        case TAG('R','L','V','3'):
+          return CONTAINER_RL2;
+        case TAG('W','V','Q','A'):
+          return CONTAINER_WSVQA;
+      }
+      break;
+    case TAG('G','I','F','8'):
+      if ((buffer[4] == '7' || buffer[4] == '9') &&
+          buffer[5] == 'a' &&
+          READ16(buffer + 6) != 0 &&
+          READ16(buffer + 8) != 0)
+        return CONTAINER_GIF;
+      break;
+    case ISS_TAG: // TAG('I','M','A','_')
+      if (memcmp(buffer, ISS_SIGNATURE, strlen(ISS_SIGNATURE)) == 0)
+        return CONTAINER_ISS;
+      break;
+    case TAG('k','!','\x00','\x40'):
+    case TAG('k','!','\x00','\x50'):
+      return CONTAINER_BIT;
+    case LXF_TAG: // TAG('L','E','I','T')
+      if (memcmp(buffer, LXF_SIGNATURE, sizeof(LXF_SIGNATURE) - 1) == 0)
+        return CONTAINER_LXF;
+      break;
+    case TAG('L','P','F',' '):
+      if (READ32(buffer + 16) == TAG('A','N','I','M') &&
+          READ16(buffer + 20) != 0 &&
+          READ16(buffer + 22) != 0)
+        return CONTAINER_ANM;
+      break;
+    case TAG('L','V','F','F'):
+      return CONTAINER_LVF;
+    case TAG('M','A','C',' '):
+      return CONTAINER_APE;
+    case TAG('M','M','M','D'):
+      if (third4 == TAG('C','N','T','I'))
+        return CONTAINER_MMF;
+      break;
+    case TAG('M','O','V','I'):
+      if (READ16(buffer + 4) < 3)
+        return CONTAINER_MV;
+      break;
+    case TAG('M','P','+','\x07'):
+    case TAG('M','P','+','\x17'):
+      return CONTAINER_MPC;
+    case TAG('M','P','C','K'):
+      if (check_mpc8(buffer, buffer_size))
+        return CONTAINER_MPC8;
+      break;
+    case TAG('N','I','S','T'):
+      if (second4 == TAG('_','1','A','\x0a'))
+        return CONTAINER_NISTSPHERE;
+      break;
+    case TAG('N','M','\x7a','\x56'):
+      if (second4 == TAG('\x1F','\x5F','\x04','\xAD'))
+        return CONTAINER_NUT;
+      break;
+    case TAG('N','S','V','f'):
+    case TAG('N','S','V','s'):
+      return CONTAINER_NSV;
+    case LIBNUT_TAG: // TAG('n','u','t','/')
+      if (memcmp(buffer, LIBNUT_SIGNATURE, strlen(LIBNUT_SIGNATURE)) == 0)
+        return CONTAINER_LIBNUT;
+      break;
+    case NUV1_TAG: // TAG('N','u','p','p')
+      if (memcmp(buffer, NUV1_SIGNATURE, strlen(NUV1_SIGNATURE)) == 0)
+        return CONTAINER_NUV;
+      break;
+    case NUV2_TAG: // TAG('M','y','t','h')
+      if (memcmp(buffer, NUV2_SIGNATURE, strlen(NUV2_SIGNATURE)) == 0)
+        return CONTAINER_NUV;
+      break;
+    case TAG('O','N','2',' '):
+      if (third4 == TAG('O','N','2','f'))
+        return CONTAINER_AVI;
+    case TAG('O','g','g','S'):
+      if (buffer[5] <= 7)
+        return CONTAINER_OGG;
+      break;
+    case PAF_TAG: // TAG('P','a','c','k')
+      if (memcmp(buffer, PAF_SIGNATURE, strlen(PAF_SIGNATURE)) == 0)
+        return CONTAINER_PAF;
+      break;
+    case TAG('p','m','p','m'):
+      if (READ32(buffer + 4) == 1)
+        return CONTAINER_PMP;
+      break;
+    case TAG('P','V','F','1'):
+      if (buffer[4] == '\n')
+        return CONTAINER_PVF;
+      break;
+    case TAG('R','F','6','4'):
+      if (READ32(buffer + 12) == TAG('d','s','6','4'))
+        return CONTAINER_WAV;
+      break;
+    case TAG('r','i','f','f'):
+      if (memcmp(buffer, W64_SIGNATURE, sizeof(W64_SIGNATURE) - 1) == 0 &&
+          memcmp(buffer + 24, W64_SIGNATURE2, sizeof(W64_SIGNATURE2) - 1) == 0)
+        return CONTAINER_W64;
+      break;
+    case TAG('R','I','F','F'):
+      switch (third4) {
+        case TAG('4','X','M','V'):
+          return CONTAINER_4XM;
+        case TAG('A','V','I',' '):
+        case TAG('A','V','I','X'):
+        case TAG('A','V','I','\x19'):
+        case TAG('A','M','V',' '):
+          return CONTAINER_AVI;
+        case TAG('Q','L','C','M'):
+          if (READ32(buffer + 12) == TAG('f','m','t',' '))
+            return CONTAINER_QCP;
+          break;
+        case TAG('W','A','V','E'):
+          // possibly ACT or WAV
+          return (check_act(buffer, buffer_size)) ?
+            CONTAINER_ACT : CONTAINER_WAV;
+        case TAG('X','W','M','A'):
+          return CONTAINER_XWMA;
+      }
+      break;
+    case TAG('R','S','T','M'):
+      next = READ16(buffer + 4);
+      if (next == 0xfffe || next == 0xfeff)
+        return CONTAINER_BRSTM;
+      break;
+    case TAG('S','A','N','M'):
+      if (third4 == TAG('S','H','D','R'))
+        return CONTAINER_SMUSH;
+      break;
+    case TAG('S','I','F','F'):
+      if (third4 == TAG('V','B','V','1') || third4 == TAG('S','O','U','N'))
+        return CONTAINER_SIFF;
+      break;
+    case TAG('S','M','K','2'):
+    case TAG('S','M','K','4'):
+      return CONTAINER_SMK;
+    case TAG('S','T','R','M'):
+      if (READ16(buffer + 10) && READ16(buffer + 12) && READ16(buffer + 16))
+        return CONTAINER_AST;
+      break;
+    case TAG('t','B','a','K'):
+      return CONTAINER_TAK;
+    case TAG('T','H','P','\x00'):
+      return CONTAINER_THP;
+    case TAG('T','M','A','V'):
+      if (check_tmv(buffer, buffer_size))
+        return CONTAINER_TMV;
+      break;
+    case TAG('T','T','A','1'):
+      return CONTAINER_TTA;
+    case TAG('\x55','\xaa','\x00','\x00'):
+      if (check_dsicin(buffer, buffer_size))
+        return CONTAINER_DSICIN;
+      break;
+    case TAG('T','W','I','N'):
+      if (check_vqf(buffer, buffer_size))
+        return CONTAINER_VQF;
+      break;
+    case TAG('V','I','D','\x00'):
+      return CONTAINER_BETHSOFTVID;
+    case TAG('w','W','\x10','\x00'):
+      return CONTAINER_AVS;
+    case TAG('w','v','p','k'):
+      return CONTAINER_WV;
+    case TAG('X','A','\x00','\x00'):
+    case TAG('X','A','I','\x00'):
+    case TAG('X','A','J','\x00'):
+      if (check_xa(buffer, buffer_size))
+        return CONTAINER_XA;
+      break;
+    case TAG('X','B','I','N'):
+      if (check_xbin(buffer, buffer_size))
+        return CONTAINER_XBIN;
+      break;
+    case YUV4_TAG: // TAG('Y','U','V','4')
+      if (memcmp(buffer, YUV4_SIGNATURE, strlen(YUV4_SIGNATURE)) == 0)
+        return CONTAINER_YUV4MPEGPIPE;
+      break;
+    case WEBVTT_TAG: // TAG('W','E','B','V')
+      if (memcmp(buffer, WEBVTT_SIGNATURE, strlen(WEBVTT_SIGNATURE)) == 0)
+        return CONTAINER_WEBVTT;
+      break;
+    case WEBVTT_BOM_TAG: // TAG('\xef','\xbb','\xbf','W')
+      if (memcmp(buffer,
+                 WEBVTT_BOM_SIGNATURE,
+                 strlen(WEBVTT_BOM_SIGNATURE)) == 0)
+        return CONTAINER_WEBVTT;
+      break;
+    case ASS_TAG: // TAG('[','S','c','r')
+      if (memcmp(buffer, ASS_SIGNATURE, strlen(ASS_SIGNATURE)) == 0)
+        return CONTAINER_ASS;
+      break;
+    case ASS_BOM_TAG: // TAG('\xef','\xbb','\xbf','[')
+      if (memcmp(buffer, ASS_BOM_SIGNATURE, strlen(ASS_BOM_SIGNATURE)) == 0)
+        return CONTAINER_ASS;
+      break;
+    case REALTEXT_TAG: // TAG('<','w','i','n')
+      if (memcmp(ptr, REALTEXT_SIGNATURE, strlen(REALTEXT_SIGNATURE)) == 0)
+        return CONTAINER_REALTEXT;
+      break;
+    case SAMI_TAG: // TAG('<','S','A','M')
+      if (memcmp(ptr, SAMI_SIGNATURE, strlen(SAMI_SIGNATURE)) == 0)
+        return CONTAINER_SAMI;
+      break;
+    case REALTEXT_BOM_TAG: // TAG('\xef','\xbb','\xbf','<')
+                           // also SAMI_BOM_TAG
+      if (memcmp(ptr,
+                 REALTEXT_BOM_SIGNATURE,
+                 strlen(REALTEXT_BOM_SIGNATURE)) == 0)
+        return CONTAINER_REALTEXT;
+      if (memcmp(ptr, SAMI_BOM_SIGNATURE, strlen(SAMI_BOM_SIGNATURE)) == 0)
+        return CONTAINER_SAMI;
+      break;
+    case WTV_TAG: // TAG('\xb7','\xd8','\x00','\x20')
+      if (memcmp(ptr, WTV_SIGNATURE, sizeof(WTV_SIGNATURE) - 1) == 0)
+        return CONTAINER_WTV;
+      break;
+  }
+
+  // Now try a few different ones that look at something other
+  // than the first 4 bytes
+  uint32_t first3 = first4 & 0xffffff00;
+  switch (first3) {
+    case TAG('A','M','V',0):
+      if (check_mtv(buffer, buffer_size))
+        return CONTAINER_MTV;
+      break;
+    case TAG('C','W','S',0):
+    case TAG('F','W','S',0):
+      return CONTAINER_SWF;
+    case TAG('F','R','M',0):
+      if (READ16(buffer + 4) != 0 && READ16(buffer + 6) != 0)
+        return CONTAINER_FRM;
+      break;
+    case TAG('A','V','\x01',0):
+    case TAG('A','V','\x02',0):
+      if (check_pva(buffer, buffer_size))
+        return CONTAINER_PVA;
+      break;
+    case TAG('I','D','3',0):
+      if (check_mp3(buffer, buffer_size, true))
+        return CONTAINER_MP3;
+      break;
+  }
+
+  // Maybe the first 2 characters are something we can use.
+  uint32_t first2 = first4 & 0xffff0000;
+  switch (first2) {
+    case 0x032e0000:
+      if (check_vmd(buffer, buffer_size))
+        return CONTAINER_VMD;
+      break;
+    case 0x04000000:
+    case 0x04040000:
+    case 0x040c0000:
+    case 0x04140000:
+      return CONTAINER_EA_CDATA;
+    case TAG('J','V',0,0):
+      if (memcmp(buffer + 4, JV_SIGNATURE, strlen(JV_SIGNATURE)) == 0)
+        return CONTAINER_JV;
+      break;
+    case 0x0b770000:
+      if (check_ac3(buffer, buffer_size))
+        return CONTAINER_AC3;
+      if (check_eac3(buffer, buffer_size))
+        return CONTAINER_EAC3;
+      break;
+    case TAG('Y','O',0,0):
+      if (check_yop(buffer, buffer_size))
+        return CONTAINER_JV;
+      break;
+  }
+
+  // Now try the second set of 4 characters.
+  switch (second4) {
+    case 4:
+      if (buffer[3] == 0xc5 && READ32(buffer + 20) == 0xc)
+        return CONTAINER_VC1TEST;
+      break;
+    case TAG('R','E','D','1'):
+      return CONTAINER_R3D;
+  }
+
+  switch (READ16(buffer + 4)) {
+    case 0xaf11:
+    case 0xaf12:
+    case 0xaf13:
+      if (third4 <= 4096 &&
+          READ16(buffer + 10) <= 4096 &&
+          (READ16(buffer + 16) == 0xf1fa || READ32(buffer + 16) <= 2000))
+        return CONTAINER_FLIC;
+      break;
+  }
+
+  // Lastly, there are some that are other simple checks but don't fit
+  // the above case statements.
+  if (check_c93(buffer, buffer_size))
+    return CONTAINER_C93;
+  if (check_cdxl(buffer, buffer_size))
+    return CONTAINER_CDXL;
+  if (check_idcin(buffer, buffer_size))
+    return CONTAINER_IDCIN;
+  if (check_mov(buffer, buffer_size))
+    return CONTAINER_MOV;
+  if (check_vivo(buffer, buffer_size))
+    return CONTAINER_VIVO;
+  if (check_wsaud(buffer, buffer_size))
+    return CONTAINER_WSAUD;
+  if (check_xmv(buffer, buffer_size))
+    return CONTAINER_XMV;
+  // Check if the file is in MP3 format without the header
+  if (check_mp3(buffer, buffer_size, false))
+    return CONTAINER_MP3;
+
+  // skip over starting 0's, and see if it is MP3/AC3/EAC3
+  if (buffer[0] == 0) {
+    size_t offset = 1;
+    size_t remaining = buffer_size - 1;
+    while (remaining > 0 && buffer[offset] == 0) {
+      ++offset;
+      --remaining;
+    }
+    if (remaining > 32) {
+      // not worth trying if only a small number of bytes left
+      if (READ16(buffer + offset) == 0x0b77) {
+        if (check_ac3(buffer + offset, remaining))
+          return CONTAINER_AC3;
+        if (check_eac3(buffer + offset, remaining))
+          return CONTAINER_EAC3;
+      }
+      else if (check_mp3(buffer, buffer_size, false))
+        return CONTAINER_MP3;
+    }
+  }
+
+  return CONTAINER_UNKNOWN;
+}
+
+static const char ipm_string[] = "Interplay MVE File\x1A\0\x1A";
+static const char mxf_string[] =
+    "\x06\x0e\x2b\x34\x02\x05\x01\x01\x0d\x01\x02\x01\x01\x02";
+static const char sub1_string[] = "******** START SCRIPT ********";
+
+// Attempt to determine the container type by scanning for a set of strings,
+// character by character. It covers the following containers:
+//   ipmovie, mxf, subviewer1
+enum FFmpegContainerName LookupContainerByStringScan(const uint8 buffer[],
+    size_t buffer_size) {
+  size_t offset = 0;
+  size_t remaining = buffer_size;
+  while (offset + 4 < buffer_size) {
+    if (buffer[offset] == ipm_string[0] &&
+        remaining >= sizeof(ipm_string) - 1 &&
+        memcmp(buffer + offset, ipm_string, sizeof(ipm_string) - 1) == 0)
+      return CONTAINER_IPMOVIE;
+
+    if (buffer[offset] == mxf_string[0] &&
+        remaining >= sizeof(mxf_string) - 1 &&
+        memcmp(buffer + offset, mxf_string, sizeof(mxf_string) - 1) == 0)
+      return CONTAINER_MXF;
+
+    if (buffer[offset] == sub1_string[0] &&
+        remaining >= sizeof(sub1_string) - 1 &&
+        memcmp(buffer + offset, sub1_string, sizeof(sub1_string) - 1) == 0)
+      return CONTAINER_SUBVIEWER1;
+
+    // Additional checks for nsv and msnwctcp.
+    uint32_t tag = READ32(buffer + offset);
+    switch (tag) {
+      case TAG('N','S','V','s'):
+        if (check_nsv(buffer + offset, remaining))
+          return CONTAINER_NSV;
+        break;
+      case 0x001800a0:
+      case 0x00180140:
+        if (check_msnwctcp(buffer + offset, remaining))
+          return CONTAINER_MSNWCTCP;
+        break;
+    }
+
+    // Not found, move forward to next character.
+    ++offset;
+    --remaining;
+  }
+
+  // didn't find a string match for any of the formats
+  return CONTAINER_UNKNOWN;
+}
+
+// Attempt to determine the container type by scanning for a set of strings,
+// line by line. It covers the following containers:
+//   microdvd, mpl2, mpsub, pjs, sdp, srt, subviewer, vplayer
+enum FFmpegContainerName LookupContainerByStringLine(const uint8 buffer[],
+    size_t buffer_size) {
+  size_t offset = memcmp(buffer, BOM, 3) == 0 ? 3 : 0;
+  size_t lines = 0;
+  char c;
+  int n;
+
+  // PJS is a scan from the beginning only.
+  if (check_pjs(buffer, buffer_size))
+    return CONTAINER_PJS;
+
+  // Same for VPLAYER.
+  if (check_vplayer(buffer, buffer_size))
+    return CONTAINER_VPLAYER;
+
+  // Assume that the longest scanf will be 100 characters.
+  while (offset + 100 < buffer_size) {
+    const char* ptr = reinterpret_cast<const char*>(buffer + offset);
+
+    if (*ptr == '{' && lines < 3) {
+      if (sscanf(ptr, "{%*d}{}%c", &c) == 1 ||
+          sscanf(ptr, "{%*d}{%*d}%c", &c) == 1 ||
+          sscanf(ptr, "{DEFAULT}{}%c", &c) == 1)
+        return CONTAINER_MICRODVD;
+    }
+
+    if (*ptr == '[' && lines < 3) {
+      if (sscanf(ptr, "[%*64d][%*64d]%c", &c) == 1 ||
+          sscanf(ptr, "[%*64d][]%c", &c) == 1)
+        return CONTAINER_MPL2;
+    }
+
+    if (*ptr == 'F') {
+      if (memcmp(ptr, "FORMAT=TIME", 11) == 0 ||
+          sscanf(ptr, "FORMAT=%d", &n) == 1)
+        return CONTAINER_MPSUB;
+    }
+
+    if (*ptr == 'c') {
+      if (memcmp(ptr, "c=IN IP", 7) == 0)
+        return CONTAINER_SDP;
+    }
+
+    if (isdigit(*ptr) && lines < 3) {
+      if (sscanf(ptr,
+                 "%*d:%*2d:%*2d%*1[,.]%*3d --> %*d:%*2d:%*2d%*1[,.]%3d",
+                 &n) == 1)
+        return CONTAINER_SRT;
+    }
+
+    if (isdigit(*ptr) && lines < 1) {
+      if (sscanf(ptr, "%*u:%*u:%*u.%*u,%*u:%*u:%*u.%*u%c", &c) == 1 ||
+          memcmp(ptr, "[INFORMATION]", 13) == 0)
+        return CONTAINER_SUBVIEWER;
+    }
+
+    // Find the end of the line.
+    while (buffer[offset] != '\n' && buffer[offset] != '\r' &&
+           offset < buffer_size)
+      ++offset;
+
+    // Skip the \n\r.
+    while ((buffer[offset] == '\n' || buffer[offset] == '\r') &&
+           offset < buffer_size)
+      ++offset;
+    ++lines;
+  }
+
+  // Didn't find a string match for any of the formats.
+  return CONTAINER_UNKNOWN;
+}
+
+// Attempt to determine the container name from the buffer provided.
+enum FFmpegContainerName ContainerNames::LookupContainer(const uint8 buffer[],
+                                                         size_t buffer_size) {
+  // TODO(jrumell): The following formats are not scanned for
+  //    aac, cavsvideo, dts, dv, h261, h263, h264, jacosub, loas,
+  //    m4v, mpeg, mpegts, mpegvideo, psxstr, sbg, spdif, tedcaptions
+
+  // First attempt the simple checks, that typically look at just the
+  // first few bytes of the file.
+  FFmpegContainerName result = LookupContainerByFirst4(buffer, buffer_size);
+  if (result != CONTAINER_UNKNOWN)
+    return result;
+
+  // No success with simple test, so attempt to determine the container by
+  // looking for strings in the buffer.
+  result = LookupContainerByStringScan(buffer, buffer_size);
+  if (result != CONTAINER_UNKNOWN)
+    return result;
+  return LookupContainerByStringLine(buffer, buffer_size);
+}
+
+// Log the container based on the name returned by FFmpeg.
+void ContainerNames::LogContainer(const char* container_name) {
+  FFmpegContainerName container = LookupContainer(container_name);
+  // Even container IDs are the ones detected by FFmpeg.
+  UMA_HISTOGRAM_ENUMERATION(
+      "Media.Container", container * 2, CONTAINER_MAX * 2);

[Ilya Sherman, 2013/04/29 23:48:06]

Can you use a sparse histogram for this histogram?  An enumerated histogram with
~450 buckets costs 450*(12 bytes per bucket) = 5.4KB, which is relatively
expensive.

[jrummell, 2013/04/30 21:36:50]

Done.

+}
+
+// Log the container by examining the first part of the stream.
+void ContainerNames::LogContainer(const uint8 buffer[], size_t buffer_size) {
+  FFmpegContainerName container = LookupContainer(buffer, buffer_size);
+  // Odd container IDs are guessed at by this code.
+  UMA_HISTOGRAM_ENUMERATION(
+      "Media.Container", container * 2 + 1, CONTAINER_MAX * 2);

[Ilya Sherman, 2013/04/29 23:48:06]

Please define a helper function along the lines of

void LogContainer(FFmpegContainerName container, bool is_guess) {
  int metric = 2 * container;
  if (is_guess)
    ++metric;

  UMA_HISTOGRAM_SPARSE_SLOWLY("Media.Container", metric);
}

This way, it's harder for the two UMA_HISTOGRAM_ENUMERATION macros to drift out
of sync with each other, e.g. by having a typo that affects only one of them.

[jrummell, 2013/04/30 21:36:50]

Great idea. Done.

+}
+
+}  // namespace media