Re-add AC3/EAC3 audio demuxing support

media/ffmpeg/ffmpeg_common.cc

 // Copyright (c) 2012 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/ffmpeg/ffmpeg_common.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/sha1.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/video_decoder_config.h"
 #include "media/base/video_util.h"
+#include "media/media_features.h"
 
 namespace media {
 
 // Why FF_INPUT_BUFFER_PADDING_SIZE? FFmpeg assumes all input buffers are
 // padded. Check here to ensure FFmpeg only receives data padded to its
 // specifications.
 static_assert(DecoderBuffer::kPaddingSize >= FF_INPUT_BUFFER_PADDING_SIZE,
               "DecoderBuffer padding size does not fit ffmpeg requirement");
 
 // Alignment requirement by FFmpeg for input and output buffers. This need to
@@ skipping 33 matching lines @@
 int64_t ConvertToTimeBase(const AVRational& time_base,
                           const base::TimeDelta& timestamp) {
   return av_rescale_q(timestamp.InMicroseconds(), kMicrosBase, time_base);
 }
 
 // Converts an FFmpeg audio codec ID into its corresponding supported codec id.
 static AudioCodec CodecIDToAudioCodec(AVCodecID codec_id) {
   switch (codec_id) {
     case AV_CODEC_ID_AAC:
       return kCodecAAC;
+#if BUILDFLAG(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+    case AV_CODEC_ID_AC3:
+      return kCodecAC3;
+    case AV_CODEC_ID_EAC3:
+      return kCodecEAC3;
+#endif
     case AV_CODEC_ID_MP3:
       return kCodecMP3;
     case AV_CODEC_ID_VORBIS:
       return kCodecVorbis;
     case AV_CODEC_ID_PCM_U8:
     case AV_CODEC_ID_PCM_S16LE:
     case AV_CODEC_ID_PCM_S24LE:
     case AV_CODEC_ID_PCM_S32LE:
     case AV_CODEC_ID_PCM_F32LE:
       return kCodecPCM;
@@ skipping 236 matching lines @@
     sample_format = kSampleFormatF32;
 
     // Always use 48kHz for OPUS.  Technically we should match to the highest
     // supported hardware sample rate among [8, 12, 16, 24, 48] kHz, but we
     // don't know the hardware sample rate at this point and those rates are
     // rarely used for output.  See the "Input Sample Rate" section of the spec:
     // http://tools.ietf.org/html/draft-terriberry-oggopus-01#page-11
     sample_rate = 48000;
   }
 
+#if BUILDFLAG(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+  // For AC3/EAC3 we enable only demuxing, but not decoding, so FFmpeg does not
+  // fill |sample_fmt|.
+  if (codec == kCodecAC3 || codec == kCodecEAC3) {
+    // The spec for AC3/EAC3 audio is ETSI TS 102 366. According to sections
+    // F.3.1 and F.5.1 in that spec the sample_format for AC3/EAC3 must be 16.
+    sample_format = kSampleFormatS16;
+  }
+#else
+  DCHECK(codec != kCodecAC3 && codec != kCodecEAC3);
+#endif
+
   base::TimeDelta seek_preroll;
   if (codec_context->seek_preroll > 0) {
     seek_preroll = base::TimeDelta::FromMicroseconds(
         codec_context->seek_preroll * 1000000.0 / codec_context->sample_rate);
   }
 
   // AVStream occasionally has invalid extra data. See http://crbug.com/517163
   if ((codec_context->extradata_size == 0) !=
       (codec_context->extradata == nullptr)) {
     LOG(ERROR) << __FUNCTION__
                << (codec_context->extradata == nullptr ? " NULL" : " Non-NULL")
                << " extra data cannot have size of "
                << codec_context->extradata_size << ".";
     return false;
   }
 
   std::vector<uint8_t> extra_data;
   if (codec_context->extradata_size > 0) {
     extra_data.assign(codec_context->extradata,
                       codec_context->extradata + codec_context->extradata_size);
   }
   config->Initialize(codec,
                      sample_format,
                      channel_layout,
                      sample_rate,
                      extra_data,
                      is_encrypted,
                      seek_preroll,
                      codec_context->delay);
-
-  if (codec != kCodecOpus) {
+  if (codec != kCodecOpus && codec != kCodecAC3 && codec != kCodecEAC3) {

[ddorwin, 2016/01/08 18:11:02]

That leaves this as the only code in this file not protected. We should be
consistent either way, though at least this would be optimized out of release
builds.

[servolk, 2016/01/08 20:02:32]

Done (and converted to switch to avoid splitting the if condition with #if
buildflag(ac3) )

+    // Verify that AudioConfig.bits_per_channel was calculated correctly for
+    // codecs that have |sample_fmt| set by FFmpeg.
     DCHECK_EQ(av_get_bytes_per_sample(codec_context->sample_fmt) * 8,
               config->bits_per_channel());
   }
 
   return true;
 }
 
 bool AVStreamToAudioDecoderConfig(const AVStream* stream,
                                   AudioDecoderConfig* config) {
   bool is_encrypted = false;
@@ skipping 323 matching lines @@
 }
 
 int32_t HashCodecName(const char* codec_name) {
   // Use the first 32-bits from the SHA1 hash as the identifier.
   int32_t hash;
   memcpy(&hash, base::SHA1HashString(codec_name).substr(0, 4).c_str(), 4);
   return hash;
 }
 
 }  // namespace media