Added aac bitstream converter

media/filters/ffmpeg_aac_bitstream_converter.cc

Index: media/filters/ffmpeg_aac_bitstream_converter.cc
diff --git a/media/filters/ffmpeg_aac_bitstream_converter.cc b/media/filters/ffmpeg_aac_bitstream_converter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d45e9c72c0ebf25f2f34e6bb55a924f4ed5846a8
--- /dev/null
+++ b/media/filters/ffmpeg_aac_bitstream_converter.cc
@@ -0,0 +1,205 @@
+// 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/filters/ffmpeg_aac_bitstream_converter.h"
+
+#include "base/logging.h"
+#include "media/ffmpeg/ffmpeg_common.h"
+
+namespace media {
+
+FFmpegAACBitstreamConverter::FFmpegAACBitstreamConverter(
+    AVCodecContext* stream_codec_context)
+    : stream_codec_context_(stream_codec_context) {
+  CHECK(stream_codec_context_);
+  header_generated_ = false;
+}
+
+FFmpegAACBitstreamConverter::~FFmpegAACBitstreamConverter() {
+}
+
+bool FFmpegAACBitstreamConverter::ConvertPacket(AVPacket* packet) {
+  int header_plus_packet_size =
+      packet->size + kAdtsHeaderSize * sizeof(unsigned char);

[DaleCurtis, 2014/10/31 21:50:15]

Is the  * sizeof(unsigned char) necessary? kAdtsHeaderSize is in bytes no? 
Ditto for everywhere else.

[kjoswiak, 2014/11/01 00:44:26]

Done.

+  if (!header_generated_) {
+    if (stream_codec_context_->extradata == 0) {

[DaleCurtis, 2014/10/31 21:50:15]

If !extradata

[kjoswiak, 2014/11/01 00:44:26]

Done.

+      DLOG(ERROR) << "extradata is null";
+      return false;
+    }
+    if (stream_codec_context_->extradata_size < 2) {
+      DLOG(ERROR) << "extradata too small to contain MP4A header";
+      return false;
+    }
+    int sample_rate_index =
+        ((stream_codec_context_->extradata[0] & 0x07) << 1) |
+        ((stream_codec_context_->extradata[1] & 0x80) >> 7);
+    if (sample_rate_index > 12) {
+      sample_rate_index = 4;
+    }
+    header_generated_ = GenerateAdtsHeader(stream_codec_context_->codec_id,
+                                           0,  // layer
+                                           stream_codec_context_->profile,
+                                           sample_rate_index,
+                                           0,  // private stream
+                                           stream_codec_context_->channels,
+                                           0,  // originality
+                                           0,  // home
+                                           0,  // copyrighted_stream
+                                           0,  // copyright start
+                                           header_plus_packet_size,
+                                           0x7FF,  // buffer fullness
+                                           0);  // one frame per packet
+  }
+
+  // Inform caller if the header generation failed.
+  if (!header_generated_)
+    return false;
+
+  // Allocate new packet for the output.
+  AVPacket dest_packet;
+  if (av_new_packet(&dest_packet, header_plus_packet_size) != 0)
+    return false;  // Memory allocation failure.
+
+  memcpy(dest_packet.data, hdr_, kAdtsHeaderSize * sizeof(unsigned char));
+  memcpy(reinterpret_cast<void*>(dest_packet.data + kAdtsHeaderSize),
+         reinterpret_cast<void*>(packet->data), packet->size);
+
+  // This is a bit tricky: since the interface does not allow us to replace
+  // the pointer of the old packet with a new one, we will initially copy the
+  // metadata from old packet to new bigger packet.
+  av_packet_copy_props(&dest_packet, packet);
+
+  // Release the old packet.
+  av_free_packet(packet);
+  *packet = dest_packet;  // Finally, replace the values in the input packet.
+
+  return true;
+}
+
+bool FFmpegAACBitstreamConverter::GenerateAdtsHeader(
+    int codec, int layer, int audio_profile, int sample_rate_index,
+    int private_stream, int channel_configuration, int originality, int home,
+    int copyrighted_stream, int copyright_start, int frame_length,
+    int buffer_fullness, int number_of_frames_minus_one) {
+  DCHECK(codec == CODEC_ID_AAC);

[DaleCurtis, 2014/10/31 21:50:15]

DCHECK_EQ

[kjoswiak, 2014/11/01 00:44:27]

Done.

+
+  memset(reinterpret_cast<void *>(hdr_), 0,

[DaleCurtis, 2014/10/31 21:50:15]

Up to you, but you can zero initialize hdr_ by specifying it in the constructor
as hdr_(),

[kjoswiak, 2014/11/01 00:44:26]

I kind of like it this way, ensures is zeroed precisely when it needs to be and
does the work on demand

+         kAdtsHeaderSize * sizeof(unsigned char));
+  // Ref: http://wiki.multimedia.cx/index.php?title=ADTS
+  // ADTS header structure is the following
+  // AAAAAAAA  AAAABCCD  EEFFFFGH  HHIJKLMM  MMMMMMMM  MMMOOOOO  OOOOOOPP
+  //
+  // A    Syncword 0xFFF, all bits must be 1
+  // B    MPEG Version: 0 for MPEG-4, 1 for MPEG-2
+  // C    Layer: always 0
+  // D    Protection absent: Set to 1 if no CRC and 0 if there is CRC.
+  // E    Profile: the MPEG-4 Audio Object Type minus 1.
+  // F    MPEG-4 Sampling Frequency Index (15 is forbidden)
+  // G    Private stream:
+  // H    MPEG-4 Channel Configuration
+  // I    Originality
+  // J    Home
+  // K    Copyrighted Stream
+  // L    Copyright start
+  // M    Frame length. This must include the ADTS header length.
+  // O    Buffer fullness
+  // P    Number of AAC frames in ADTS frame minus 1.
+  //      For maximum compatibility always use 1 AAC frame per ADTS frame.
+
+  // Syncword
+  hdr_[0] = 0xFF;
+  hdr_[1] = 0xF0;
+
+  // Layer is always 0. No further action required.
+
+  // Protection absent (no CRC) is always 1.
+  hdr_[1] |= 1;
+
+  switch (audio_profile) {
+    case FF_PROFILE_AAC_MAIN:
+      break;
+    case FF_PROFILE_AAC_LOW:
+      hdr_[2] |= (1 << 6);
+      break;
+    case FF_PROFILE_AAC_SSR:
+      hdr_[2] |= (2 << 6);
+      break;
+    case FF_PROFILE_AAC_LTP:
+      hdr_[2] |= (3 << 6);
+      break;
+  }
+
+  hdr_[2] |= ((sample_rate_index & 0xf) << 2);
+
+  if (private_stream)
+    hdr_[2] |= (1 << 1);
+
+  switch (channel_configuration) {
+    case 1:
+      // front-center
+      hdr_[3] |= (1 << 6);
+      break;
+    case 2:
+      // front-left, front-right
+      hdr_[3] |= (2 << 6);
+      break;
+    case 3:
+      // front-center, front-left, front-right
+      hdr_[3] |= (3 << 6);
+      break;
+    case 4:
+      // front-center, front-left, front-right, back-center
+      hdr_[2] |= 1;
+      break;
+    case 5:
+      // front-center, front-left, front-right, back-left, back-right
+      hdr_[2] |= 1;
+      hdr_[3] |= (1 << 6);
+      break;
+    case 6:
+      // front-center, front-left, front-right, back-left, back-right,
+      // LFE-channel
+      hdr_[2] |= 1;
+      hdr_[3] |= (2 << 6);
+      break;
+    case 7:
+      // front-center, front-left, front-right, side-left, side-right,
+      // back-left, back-right, LFE-channel
+      hdr_[2] |= 1;
+      hdr_[3] |= (3 << 6);
+      break;
+    default:
+      DLOG(ERROR) << "[" << __FUNCTION__ << "] "
+                  << "unsupported number of audio channels:"
+                  << channel_configuration;
+      return false;
+  }
+
+  if (originality)
+    hdr_[3] |= (1 << 5);
+
+  if (home)
+    hdr_[3] |= (1 << 4);
+
+  if (copyrighted_stream)
+    hdr_[3] |= (1 << 3);
+
+  if (copyright_start)
+    hdr_[3] |= (1 << 2);
+
+  // frame length
+  hdr_[3] |= (frame_length >> 11) & 0x03;
+  hdr_[4] = (frame_length >> 3) & 0xFF;
+  hdr_[5] |= (frame_length & 7) << 5;
+
+  // buffer fullness
+  hdr_[5] |= (buffer_fullness >> 6) & 0x1F;
+  hdr_[6] |= (buffer_fullness & 0x3F) << 2;
+
+  hdr_[6] |= number_of_frames_minus_one & 0x3;
+
+  return true;
+}
+
+}  // namespace media