Implement experimental MP3 support for Media Source API.

media/mp3/mp3_stream_parser.cc

+// 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/mp3/mp3_stream_parser.h"
+
+#include "base/bind.h"
+#include "base/callback_helpers.h"
+#include "base/message_loop/message_loop.h"
+#include "media/base/bit_reader.h"
+#include "media/base/buffers.h"
+#include "media/base/stream_parser_buffer.h"
+#include "media/base/video_decoder_config.h"
+
+namespace media {
+namespace mp3 {
+
+static const uint32 kMP3StartCodeMask = 0xffe00000;
+static const uint32 kICYStartCode = 0x49435920; // 'ICY '

[scherkus (not reviewing), 2013/09/03 19:34:22]

does this permit appending of icecast streams?

should we add a test for that?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Yes.
Yeah. I'll add a version of sfx.mp3 with an icecast header prepended to it.

+static const int kMaxIcecastHeaderSize = 4096;

[scherkus (not reviewing), 2013/09/03 19:34:22]

is this arbitrary? if so, I'd mention it is

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+
+static const uint32 kID3StartCodeMask = 0xffffff00;
+static const uint32 kID3v1StartCode = 0x54414700; // 'TAG\0'
+static const int kID3v1Size = 128;
+static const int kID3v1ExtendedSize = 227;
+static const uint32 kID3v2StartCode = 0x49443300; // 'ID3\0'
+
+// Map that determined which bitrate_index & channel_mode combinations

[scherkus (not reviewing), 2013/09/03 19:34:22]

s/determined/determines/?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+// are allowed.
+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|.
+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.
+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.
+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 }
+};
+
+MP3StreamParser::MP3StreamParser()
+    : state_(UNINITIALIZED),
+      in_media_segment_(false) {
+}
+
+MP3StreamParser::~MP3StreamParser() {}
+
+void MP3StreamParser::Init(const InitCB& init_cb,
+                           const NewConfigCB& config_cb,
+                           const NewBuffersCB& new_buffers_cb,
+                           const NewTextBuffersCB& text_cb,
+                           const NeedKeyCB& need_key_cb,
+                           const AddTextTrackCB& add_text_track_cb,
+                           const NewMediaSegmentCB& new_segment_cb,
+                           const base::Closure& end_of_segment_cb,
+                           const LogCB& log_cb) {
+  DVLOG(1) << __FUNCTION__;
+  DCHECK_EQ(state_, UNINITIALIZED);
+  init_cb_ = init_cb;
+  config_cb_ = config_cb;
+  new_buffers_cb_ = new_buffers_cb;
+  new_segment_cb_ = new_segment_cb;
+  end_of_segment_cb_ = end_of_segment_cb;
+  log_cb_ = log_cb;
+
+  ChangeState(INITIALIZED);
+}
+
+void MP3StreamParser::Flush() {
+  DVLOG(1) << __FUNCTION__;
+  DCHECK_NE(state_, UNINITIALIZED);
+  queue_.Reset();
+  timestamp_helper_->SetBaseTimestamp(base::TimeDelta());
+  in_media_segment_ = false;
+}
+
+bool MP3StreamParser::Parse(const uint8* buf, int size) {
+  DVLOG(1) << __FUNCTION__ << "(" << size << ")";
+  DCHECK(buf);
+  DCHECK_GT(size, 0);
+  DCHECK_NE(state_, UNINITIALIZED);
+
+  if (state_ == PARSE_ERROR)
+    return false;
+
+  DCHECK_EQ(state_, INITIALIZED);
+
+  queue_.Push(buf, size);
+
+  for (;;) {
+    const uint8* data;
+    int data_size;
+    queue_.Peek(&data, &data_size);
+
+    if (size < 4)
+      return true;
+
+    uint32 start_code = data[0] << 24 | data[1] << 16 | data[2] << 8 | data[3];
+    int bytes_read = 0;
+    if ((start_code & kMP3StartCodeMask) == kMP3StartCodeMask) {
+      bytes_read = ParseMP3Frame(data, data_size);
+    } else if (start_code == kICYStartCode) {
+      bytes_read = ParseIcecastHeader(data, data_size);
+    } else if ((start_code & kID3StartCodeMask) == kID3v1StartCode) {
+      bytes_read = ParseID3v1(data, data_size);
+    } else if ((start_code & kID3StartCodeMask) == kID3v2StartCode) {
+      bytes_read = ParseID3v2(data, data_size);
+    } else {
+      bytes_read = FindNextValidStartCode(data, data_size);
+
+      if (bytes_read > 0) {
+        DVLOG(1) << "Unexpected start code 0x" << std::hex << start_code;
+        DVLOG(1) << "SKIPPING " << bytes_read << " bytes of garbage.";
+      }
+    }
+
+    CHECK_LE(bytes_read, data_size);
+
+    if (bytes_read < 0) {
+      ChangeState(PARSE_ERROR);
+      return false;
+    } else if (bytes_read == 0) {
+      // Need more data.
+      return true;
+    }
+
+    queue_.Pop(bytes_read);
+  }
+
+  return true;
+}
+
+void MP3StreamParser::ChangeState(State state) {
+  DVLOG(1) << __FUNCTION__ << "() : " << state_ << " -> " << state;
+  state_ = state;
+}
+
+int MP3StreamParser::ParseFrameHeader(const uint8* data, int size,

[scherkus (not reviewing), 2013/09/03 19:34:22]

there's a lot of magic constants in here that might be worth beefing up w/ docs
and/or URLs to the spec and/or units

for example, that 1152 samples is a constant as defined in the spec for version
3 and how the value 144 relates to that number

also I think that "144" needs to be "72" when version != 3 :)

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.
I've updated the code w/ help from the Internets and FFmpeg code. The necessary
change was a little more involved, but you were right that the sample count
wasn't right. I think the results are a little more readable now.

+                                      int* frame_size,
+                                      int* sample_rate,
+                                      ChannelLayout* channel_layout,
+                                      int* sample_count) 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 == 0 ||
+      layer == 0 ||
+      bitrate_index == 0x0 || bitrate_index == 0xf ||
+      sample_rate_index == 0x3) {
+    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 == 2 && 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;
+
+  *frame_size = 144 * bitrate * 1000 / frame_sample_rate;
+
+  if (has_padding)
+    *frame_size += (layer == 0x3) ? 4 : 1;
+
+  if (channel_layout) {
+    *channel_layout =
+        (channel_mode == 3) ? CHANNEL_LAYOUT_MONO : CHANNEL_LAYOUT_STEREO;

[scherkus (not reviewing), 2013/09/03 19:34:22]

for this one it might be nice to call out that stereo (0), joint stereo (1), and
dual channel (2) all get collapsed into stereo output since that's information
for a decoder, etc...

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+  }
+
+  if (sample_count)
+    *sample_count = (version == 3) ? 1152 : 576;
+
+  return 4;
+}
+
+int MP3StreamParser::ParseMP3Frame(const uint8* data, int size) {
+  DVLOG(2) << __FUNCTION__ << "(" << size << ")";
+
+  int sample_rate;
+  ChannelLayout channel_layout;
+  int frame_size;
+  int sample_count;
+  int bytes_read = ParseFrameHeader(
+      data, size, &frame_size, &sample_rate, &channel_layout, &sample_count);
+
+  if (bytes_read <= 0)
+    return bytes_read;
+
+  // Make sure data contains the entire frame.
+  if (size < frame_size)
+    return 0;
+
+  DVLOG(2) << " sample_rate " << sample_rate
+           << " channel_layout " << channel_layout
+           << " frame_size " << frame_size;
+
+  if (config_.IsValidConfig() &&
+      (config_.samples_per_second() != sample_rate ||

[scherkus (not reviewing), 2013/09/03 19:34:22]

I thought MP3s maintained the same sample rate / channel layout

does this mean we can append mp3 frame data with changing audio configs?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

I believe this is only by convention. I believe that compliant decoders are
supposed to handle changes in these fields, but early ones probably didn't so
people avoided changing them in a single file.
Yes. This makes these changes look like what would happen if vorbis w/ different
sample rates * channel layouts were appended. That way once we actually support
sample rate changes, it should... "just work".... :)

+       config_.channel_layout() != channel_layout)) {
+    // Clear config data so that a config change is initiated.
+    config_ = AudioDecoderConfig();
+  }
+
+  if (!config_.IsValidConfig()) {
+    config_.Initialize(kCodecMP3, kSampleFormatF32, channel_layout,
+                       sample_rate, NULL, 0, false, false);
+
+    base::TimeDelta base_timestamp;
+    if (timestamp_helper_)
+      base_timestamp = timestamp_helper_->GetTimestamp();
+
+    timestamp_helper_.reset(new AudioTimestampHelper(sample_rate));
+    timestamp_helper_->SetBaseTimestamp(base_timestamp);
+
+    VideoDecoderConfig video_config;
+    bool success = config_cb_.Run(config_, video_config);
+
+    if (!init_cb_.is_null())
+      base::ResetAndReturn(&init_cb_).Run(success, kInfiniteDuration());
+
+    if (!success)
+      return -1;
+  }
+
+  if (!in_media_segment_) {
+    in_media_segment_ = true;
+    new_segment_cb_.Run();
+  }
+
+  BufferQueue audio_buffers;
+  BufferQueue video_buffers;
+
+  // TODO(acolwell): Change this code to parse as many frames as
+  // possible before calling new_buffers_cb_.

[scherkus (not reviewing), 2013/09/03 19:34:22]

|new_buffers_cb_|

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+  scoped_refptr<StreamParserBuffer> buffer =
+      StreamParserBuffer::CopyFrom(data, frame_size, true);
+  audio_buffers.push_back(buffer);
+
+  if (!new_buffers_cb_.Run(audio_buffers, video_buffers))
+    return -1;
+
+  timestamp_helper_->AddFrames(sample_count);
+
+  return frame_size;
+}
+
+int MP3StreamParser::ParseIcecastHeader(const uint8* data, int size) {
+  DVLOG(1) << "ParseIcecastHeader(" << size << ")";

[scherkus (not reviewing), 2013/09/03 19:34:22]

__FUNCTION__

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+
+  if (size < 4)
+    return 0;
+
+  if (memcmp("ICY ", data, 4))

[scherkus (not reviewing), 2013/09/03 19:34:22]

after checking for ICY I believe you can use HttpUtil::LocateEndOfHeaders() to
grab the int offset

doing so would require putting an explicit dependency on media in media.gyp and
media/DEPS (AFAIK we already depend on net implicitly since media depends on
ui.gyp:ui, which depends on net.gyp:net)

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+    return -1;
+
+  const uint8* end = data + size;

[scherkus (not reviewing), 2013/09/03 19:34:22]

would it be preferable to cast start/end to const char* and use str functions
instead of mem?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

The str functions would treat \0 in a special way. We don't want that.

+  for (const uint8* start = data; start < end; ++start) {

[scherkus (not reviewing), 2013/09/03 19:34:22]

s/start/pos/?

my initial scan through this code made me think start wasn't going to be
modified

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+    int bytes_left = end - start;
+    const uint8* end_of_line =
+        static_cast<const uint8*>(memchr(start, '\r', bytes_left));
+    if (end_of_line == NULL)
+      break;
+
+    // TODO(acolwell): Add code to actually parse header lines.

[scherkus (not reviewing), 2013/09/03 19:34:22]

OOC what sort of information can we get out of the headers?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Title, author, copyright, bitrate... and whether the inband metadata feature is
turned on. In a followup CL I may try to add support for the inband metadata,
but it will likely be a PitA so parsing the headers would at least allow us to
reject such streams if we happened to encounter them.

+
+    start = end_of_line;
+    bytes_left = end - start;
+
+    if (bytes_left < 4)
+      return 0;
+
+    if (!memcmp("\r\n\r\n", start, 4)) {
+      start += 4;
+      return start - data;
+    }
+  }
+
+  if (size > kMaxIcecastHeaderSize) {
+    MEDIA_LOG(log_cb_) << "Icecast header is too large. ";

[scherkus (not reviewing), 2013/09/03 19:34:22]

remove extra trailing space in " "

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+    return -1;
+  }
+
+  return 0;
+}
+
+int MP3StreamParser::ParseID3v1(const uint8* data, int size) {
+  DVLOG(1) << __FUNCTION__ << "(" << size << ")";
+
+  if (size < kID3v1Size)
+    return 0;
+
+  // TODO(acolwell): Add code to actually validate ID3v1 data and
+  // expose it as a metadata text track.
+  return (!memcmp(data, "TAG+", 4)) ? kID3v1ExtendedSize : kID3v1Size;

[scherkus (not reviewing), 2013/09/03 19:34:22]

nit: remove the extra () in first clause?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Done.

+}
+
+int MP3StreamParser::ParseID3v2(const uint8* data, int size) {
+  DVLOG(1) << __FUNCTION__ << "(" << size << ")";
+
+  if (size < 10)
+    return 0;
+
+  BitReader reader(data, size);
+  int32 id;
+  int version;
+  uint8 flags;
+  int32 id3_size;
+
+  if (!reader.ReadBits(24, &id) ||
+      !reader.ReadBits(16, &version) ||
+      !reader.ReadBits(8, &flags) ||
+      !ParseSyncSafeInt(&reader, &id3_size)) {
+    return -1;
+  }
+
+  int32 actual_tag_size = 10 + id3_size;
+
+  // Increment size if 'Footer present' flag is set.
+  if (flags & 0x10)
+    actual_tag_size += 10;
+
+  // Make sure we have the entire tag.
+  if (size < actual_tag_size)
+    return 0;
+
+  // TODO(acolwell): Add code to actually validate ID3v2 data and
+  // expose it as a metadata text track.
+  return actual_tag_size;
+}
+
+bool MP3StreamParser::ParseSyncSafeInt(BitReader* reader, int32* value) {
+  *value = 0;
+  for (int i = 0; i < 4; ++i) {
+    uint8 tmp;
+    if (!reader->ReadBits(1, &tmp) || tmp != 0) {
+      MEDIA_LOG(log_cb_) << "ID3 syncsafe integer byte MSb is not 0!";
+      return false;
+    }
+
+    if (!reader->ReadBits(7, &tmp))
+      return false;
+
+    *value <<= 7;
+    *value += tmp;
+  }
+
+  return true;
+}
+
+int MP3StreamParser::FindNextValidStartCode(const uint8* data, int size) const {
+  const uint8* start = data;
+  const uint8* end = data + size;
+
+  while (start < end) {
+    int bytes_left = end - start;
+    const uint8* candidate_start_code =
+        static_cast<const uint8*>(memchr(start, 0xff, bytes_left));
+
+    if (!candidate_start_code)
+      return 0;
+
+    bool parse_header_failed = false;
+    const uint8* sync = candidate_start_code;
+    // Try to find 3 valid frames in a row.

[scherkus (not reviewing), 2013/09/03 19:34:22]

OOC why 3?

[acolwell GONE FROM CHROMIUM, 2013/09/04 00:48:13]

Updated the comment. Checking for only 2 headers in a row can lead to false
positives. 3 decreases this probability.

+    for (int i = 0; i < 3; ++i) {
+      int sync_size = end - sync;
+      int frame_size;
+      int sync_bytes = ParseFrameHeader(
+          sync, sync_size, &frame_size, NULL, NULL, NULL);
+
+      if (sync_bytes == 0)
+        return 0;
+
+      if (sync_bytes > 0) {
+        DCHECK_LT(sync_bytes, sync_size);
+
+        // Skip over this frame so we can check the next one.
+        sync += frame_size;
+
+        // Make sure the next frame starts inside the buffer.
+        if (sync >= end)
+          return 0;
+      } else {
+        DVLOG(1) << "ParseFrameHeader() " << i << " failed @" << (sync - data);
+        parse_header_failed = true;
+        break;
+      }
+    }
+
+    if (parse_header_failed) {
+      // One of the frame header parses failed so |candidate_start_code|
+      // did not point to the start of a real frame. Move |start| forward
+      // so we can find the next candidate.
+      start = candidate_start_code + 1;
+      continue;
+    }
+
+    return candidate_start_code - data;
+  }
+
+  return 0;
+}
+
+}  // namespace mp3
+}  // namespace media