Support MPEG1 audio in the MPEG2-TS stream parser.

media/formats/mpeg/mp3_stream_parser.cc

-// Copyright 2014 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/formats/mpeg/mp3_stream_parser.h"
-
-namespace media {
-
-static const uint32 kMP3StartCodeMask = 0xffe00000;
-
-// Map that determines which bitrate_index & channel_mode combinations
-// are allowed.
-// Derived from: http://mpgedit.org/mpgedit/mpeg_format/MP3Format.html
-static const bool kIsAllowed[17][4] = {
-  { true, true, true, true },      // free
-  { true, false, false, false },   // 32
-  { true, false, false, false },   // 48
-  { true, false, false, false },   // 56
-  { true, true, true, true },      // 64
-  { true, false, false, false },   // 80
-  { true, true, true, true },      // 96
-  { true, true, true, true },      // 112
-  { true, true, true, true },      // 128
-  { true, true, true, true },      // 160
-  { true, true, true, true },      // 192
-  { false, true, true, true },     // 224
-  { false, true, true, true },     // 256
-  { false, true, true, true },     // 320
-  { false, true, true, true },     // 384
-  { false, false, false, false }   // bad
-};
-
-// Maps version and layer information in the frame header
-// into an index for the |kBitrateMap|.
-// Derived from: http://mpgedit.org/mpgedit/mpeg_format/MP3Format.html
-static const int kVersionLayerMap[4][4] = {
-  // { reserved, L3, L2, L1 }
-  { 5, 4, 4, 3 },  // MPEG 2.5
-  { 5, 5, 5, 5 },  // reserved
-  { 5, 4, 4, 3 },  // MPEG 2
-  { 5, 2, 1, 0 }   // MPEG 1
-};
-
-// Maps the bitrate index field in the header and an index
-// from |kVersionLayerMap| to a frame bitrate.
-// Derived from: http://mpgedit.org/mpgedit/mpeg_format/MP3Format.html
-static const int kBitrateMap[16][6] = {
-  // { V1L1, V1L2, V1L3, V2L1, V2L2 & V2L3, reserved }
-  { 0, 0, 0, 0, 0, 0 },
-  { 32, 32, 32, 32, 8, 0 },
-  { 64, 48, 40, 48, 16, 0 },
-  { 96, 56, 48, 56, 24, 0 },
-  { 128, 64, 56, 64, 32, 0 },
-  { 160, 80, 64, 80, 40, 0 },
-  { 192, 96, 80, 96, 48, 0 },
-  { 224, 112, 96, 112, 56, 0 },
-  { 256, 128, 112, 128, 64, 0 },
-  { 288, 160, 128, 144, 80, 0 },
-  { 320, 192, 160, 160, 96, 0 },
-  { 352, 224, 192, 176, 112, 0 },
-  { 384, 256, 224, 192, 128, 0 },
-  { 416, 320, 256, 224, 144, 0 },
-  { 448, 384, 320, 256, 160, 0 },
-  { 0, 0, 0, 0, 0}
-};
-
-// Maps the sample rate index and version fields from the frame header
-// to a sample rate.
-// Derived from: http://mpgedit.org/mpgedit/mpeg_format/MP3Format.html
-static const int kSampleRateMap[4][4] = {
-  // { V2.5, reserved, V2, V1 }
-  { 11025, 0, 22050, 44100 },
-  { 12000, 0, 24000, 48000 },
-  { 8000, 0, 16000, 32000 },
-  { 0, 0, 0, 0 }
-};
-
-// Offset in bytes from the end of the MP3 header to "Xing" or "Info" tags which
-// indicate a frame is silent metadata frame.  Values taken from FFmpeg.
-static const int kXingHeaderMap[2][2] = {{32, 17}, {17, 9}};
-
-// Frame header field constants.
-static const int kVersion2 = 2;
-static const int kVersionReserved = 1;
-static const int kVersion2_5 = 0;
-static const int kLayerReserved = 0;
-static const int kLayer1 = 3;
-static const int kLayer2 = 2;
-static const int kLayer3 = 1;
-static const int kBitrateFree = 0;
-static const int kBitrateBad = 0xf;
-static const int kSampleRateReserved = 3;
-static const int kCodecDelay = 529;
-
-MP3StreamParser::MP3StreamParser()
-    : MPEGAudioStreamParserBase(kMP3StartCodeMask, kCodecMP3, kCodecDelay) {}
-
-MP3StreamParser::~MP3StreamParser() {}
-
-int MP3StreamParser::ParseFrameHeader(const uint8* data,
-                                      int size,
-                                      int* frame_size,
-                                      int* sample_rate,
-                                      ChannelLayout* channel_layout,
-                                      int* sample_count,
-                                      bool* metadata_frame) const {
-  DCHECK(data);
-  DCHECK_GE(size, 0);
-  DCHECK(frame_size);
-
-  if (size < 4)
-    return 0;
-
-  BitReader reader(data, size);
-  int sync;
-  int version;
-  int layer;
-  int is_protected;
-  int bitrate_index;
-  int sample_rate_index;
-  int has_padding;
-  int is_private;
-  int channel_mode;
-  int other_flags;
-
-  if (!reader.ReadBits(11, &sync) ||
-      !reader.ReadBits(2, &version) ||
-      !reader.ReadBits(2, &layer) ||
-      !reader.ReadBits(1, &is_protected) ||
-      !reader.ReadBits(4, &bitrate_index) ||
-      !reader.ReadBits(2, &sample_rate_index) ||
-      !reader.ReadBits(1, &has_padding) ||
-      !reader.ReadBits(1, &is_private) ||
-      !reader.ReadBits(2, &channel_mode) ||
-      !reader.ReadBits(6, &other_flags)) {
-    return -1;
-  }
-
-  DVLOG(2) << "Header data :" << std::hex
-           << " sync 0x" << sync
-           << " version 0x" << version
-           << " layer 0x" << layer
-           << " bitrate_index 0x" << bitrate_index
-           << " sample_rate_index 0x" << sample_rate_index
-           << " channel_mode 0x" << channel_mode;
-
-  if (sync != 0x7ff ||
-      version == kVersionReserved ||
-      layer == kLayerReserved ||
-      bitrate_index == kBitrateFree || bitrate_index == kBitrateBad ||
-      sample_rate_index == kSampleRateReserved) {
-    MEDIA_LOG(log_cb()) << "Invalid header data :" << std::hex
-                        << " sync 0x" << sync
-                        << " version 0x" << version
-                        << " layer 0x" << layer
-                        << " bitrate_index 0x" << bitrate_index
-                        << " sample_rate_index 0x" << sample_rate_index
-                        << " channel_mode 0x" << channel_mode;
-    return -1;
-  }
-
-  if (layer == kLayer2 && kIsAllowed[bitrate_index][channel_mode]) {
-    MEDIA_LOG(log_cb()) << "Invalid (bitrate_index, channel_mode) combination :"
-                        << std::hex
-                        << " bitrate_index " << bitrate_index
-                        << " channel_mode " << channel_mode;
-    return -1;
-  }
-
-  int bitrate = kBitrateMap[bitrate_index][kVersionLayerMap[version][layer]];
-
-  if (bitrate == 0) {
-    MEDIA_LOG(log_cb()) << "Invalid bitrate :" << std::hex
-                        << " version " << version
-                        << " layer " << layer
-                        << " bitrate_index " << bitrate_index;
-    return -1;
-  }
-
-  DVLOG(2) << " bitrate " << bitrate;
-
-  int frame_sample_rate = kSampleRateMap[sample_rate_index][version];
-  if (frame_sample_rate == 0) {
-    MEDIA_LOG(log_cb()) << "Invalid sample rate :" << std::hex
-                        << " version " << version
-                        << " sample_rate_index " << sample_rate_index;
-    return -1;
-  }
-
-  if (sample_rate)
-    *sample_rate = frame_sample_rate;
-
-  // http://teslabs.com/openplayer/docs/docs/specs/mp3_structure2.pdf
-  // Table 2.1.5
-  int samples_per_frame;
-  switch (layer) {
-    case kLayer1:
-      samples_per_frame = 384;
-      break;
-
-    case kLayer2:
-      samples_per_frame = 1152;
-      break;
-
-    case kLayer3:
-      if (version == kVersion2 || version == kVersion2_5)
-        samples_per_frame = 576;
-      else
-        samples_per_frame = 1152;
-      break;
-
-    default:
-      return -1;
-  }
-
-  if (sample_count)
-    *sample_count = samples_per_frame;
-
-  // http://teslabs.com/openplayer/docs/docs/specs/mp3_structure2.pdf
-  // Text just below Table 2.1.5.
-  if (layer == kLayer1) {
-    // This formulation is a slight variation on the equation below,
-    // but has slightly different truncation characteristics to deal
-    // with the fact that Layer 1 has 4 byte "slots" instead of single
-    // byte ones.
-    *frame_size = 4 * (12 * bitrate * 1000 / frame_sample_rate);
-  } else {
-    *frame_size =
-        ((samples_per_frame / 8) * bitrate * 1000) / frame_sample_rate;
-  }
-
-  if (has_padding)
-    *frame_size += (layer == kLayer1) ? 4 : 1;
-
-  if (channel_layout) {
-    // Map Stereo(0), Joint Stereo(1), and Dual Channel (2) to
-    // CHANNEL_LAYOUT_STEREO and Single Channel (3) to CHANNEL_LAYOUT_MONO.
-    *channel_layout =
-        (channel_mode == 3) ? CHANNEL_LAYOUT_MONO : CHANNEL_LAYOUT_STEREO;
-  }
-
-  if (metadata_frame)
-    *metadata_frame = false;
-
-  const int header_bytes_read = reader.bits_read() / 8;
-  if (layer != kLayer3)
-    return header_bytes_read;
-
-  // Check if this is a XING frame and tell the base parser to skip it if so.
-  const int xing_header_index =
-      kXingHeaderMap[version == kVersion2 ||
-                     version == kVersion2_5][channel_mode == 3];
-  uint32_t tag = 0;
-
-  // It's not a XING frame if the frame isn't big enough to be one.
-  if (*frame_size <
-      header_bytes_read + xing_header_index + static_cast<int>(sizeof(tag))) {
-    return header_bytes_read;
-  }
-
-  // If we don't have enough data available to check, return 0 so frame parsing
-  // will be retried once more data is available.
-  if (!reader.SkipBits(xing_header_index * 8) ||
-      !reader.ReadBits(sizeof(tag) * 8, &tag)) {
-    return 0;
-  }
-
-  // Check to see if the tag contains 'Xing' or 'Info'
-  if (tag == 0x496e666f || tag == 0x58696e67) {
-    MEDIA_LOG(log_cb()) << "Skipping XING header.";
-    if (metadata_frame)
-      *metadata_frame = true;
-    return reader.bits_read() / 8;
-  }
-
-  // If it wasn't a XING frame, just return the number consumed bytes.
-  return header_bytes_read;
-}
-
-}  // namespace media