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 78b7dcdae86fcda364f40f69d8404010e65c84cb..bab4029473cfe2d8807e333f6cea0201c4061841 100644
--- a/media/formats/mp4/mp4_stream_parser.cc
+++ b/media/formats/mp4/mp4_stream_parser.cc
@@ -216,9 +216,16 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       const AudioSampleEntry& entry = samp_descr.audio_entries[desc_idx];
       const AAC& aac = entry.esds.aac;
 
-      if (!(entry.format == FOURCC_MP4A ||
-            (entry.format == FOURCC_ENCA &&
-             entry.sinf.format.format == FOURCC_MP4A))) {
+      FourCC audio_format = (entry.format == FOURCC_ENCA)
+                                ? entry.sinf.format.format
+                                : entry.format;
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+      if (audio_format != FOURCC_MP4A && audio_format != FOURCC_A52 &&
+          audio_format != FOURCC_A52b && audio_format != FOURCC_AC3 &&
+          audio_format != FOURCC_AC_3 && audio_format != FOURCC_EAC3) {
+#else
+      if (audio_format != FOURCC_MP4A) {
+#endif
         MEDIA_LOG(ERROR, media_log_) << "Unsupported audio format 0x"
                                      << std::hex << entry.format
                                      << " in stsd box.";
@@ -226,6 +233,17 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
       }
 
       uint8 audio_type = entry.esds.object_type;
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+      if (audio_type == kForbidden &&
+          (audio_format == FOURCC_EAC3 || audio_format == FOURCC_A52b)) {
+        audio_type = kEAC3;
+      }
+      if (audio_type == kForbidden &&
+          (audio_format == FOURCC_A52 || audio_format == FOURCC_AC3 ||
+           audio_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(ERROR, media_log_)
@@ -248,6 +266,16 @@ 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(ERROR, media_log_) << "Unsupported audio object type 0x"
                                      << std::hex << audio_type << " in esds.";