Re-add AC3/EAC3 audio demuxing support

media/formats/mp4/mp4_stream_parser.cc

Index: media/formats/mp4/mp4_stream_parser.cc
diff --git a/media/formats/mp4/mp4_stream_parser.cc b/media/formats/mp4/mp4_stream_parser.cc
index d4f63cbd3b76b4d01c8144e564a7bee685791409..65cc3ad1ad9de5530095c1f6468f2507514922a6 100644
--- a/media/formats/mp4/mp4_stream_parser.cc
+++ b/media/formats/mp4/mp4_stream_parser.cc
@@ -215,6 +215,13 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       const AAC& aac = entry.esds.aac;
 
       if (!(entry.format == FOURCC_MP4A ||
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+            entry.format == FOURCC_A52  ||
+            entry.format == FOURCC_A52b ||
+            entry.format == FOURCC_AC3  ||
+            entry.format == FOURCC_AC_3 ||
+            entry.format == FOURCC_EAC3 ||
+#endif
             (entry.format == FOURCC_ENCA &&
              entry.sinf.format.format == FOURCC_MP4A))) {
         MEDIA_LOG(log_cb_) << "Unsupported audio format 0x"
@@ -223,6 +230,17 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       }
 
       uint8 audio_type = entry.esds.object_type;
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+      if (audio_type == kForbidden &&
+          (entry.format == FOURCC_EAC3 || entry.format == FOURCC_A52b)) {
+        audio_type = kEAC3;
+      }
+      if (audio_type == kForbidden &&
+          (entry.format == FOURCC_A52 || entry.format == FOURCC_AC3 ||
+           entry.format == FOURCC_AC_3)) {
+        audio_type = kAC3;
+      }
+#endif
       DVLOG(1) << "audio_type " << std::hex << static_cast<int>(audio_type);
       if (audio_object_types_.find(audio_type) == audio_object_types_.end()) {
         MEDIA_LOG(log_cb_) << "audio object type 0x" << std::hex << audio_type
@@ -244,6 +262,16 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
 #if defined(OS_ANDROID)
         extra_data = aac.codec_specific_data();
 #endif
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+      } else if (audio_type == kAC3) {
+        codec = kCodecAC3;
+        channel_layout = GuessChannelLayout(entry.channelcount);
+        sample_per_second = entry.samplerate;
+      } else if (audio_type == kEAC3) {
+        codec = kCodecEAC3;
+        channel_layout = GuessChannelLayout(entry.channelcount);
+        sample_per_second = entry.samplerate;
+#endif
       } else {
         MEDIA_LOG(log_cb_) << "Unsupported audio object type 0x" << std::hex
                            << audio_type << " in esds.";