Re-add AC3/EAC3 audio demuxing support

media/base/mime_util.cc

Index: media/base/mime_util.cc
diff --git a/media/base/mime_util.cc b/media/base/mime_util.cc
index 73cddfdb7a3f9dff5c5fcff50e0cc707d0f462cc..63e97b73b3bc3037a129e88c28e9de8cd300e610 100644
--- a/media/base/mime_util.cc
+++ b/media/base/mime_util.cc
@@ -40,6 +40,11 @@ class MimeUtil {
     VP8,
     VP9,
     THEORA
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)

[ddorwin, 2015/11/25 22:24:08]

Do we need to ifdef this? There are other proprietary codecs, including HEVC,
that are not and the previous files did not.

Yes, it is dead code on most platforms, but this also hurts readability.

[servolk, 2015/12/03 00:56:14]

Done.

+    ,
+    AC3,

[ddorwin, 2015/11/25 22:24:08]

Regardless, keep similar types (at least audio) together. There is no indication
that this list cannot be modified.

[servolk, 2015/12/03 00:56:15]

Done.

+    EAC3
+#endif
   };
 
   bool IsSupportedMediaMimeType(const std::string& mime_type) const;
@@ -217,6 +222,13 @@ static bool IsCodecSupportedOnAndroid(MimeUtil::Codec codec) {
       // MPEG-2 variants of AAC are not supported on Android.
       return false;
 
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+    case MimeUtil::AC3:
+    case MimeUtil::EAC3:
+      // TODO(servolk): Revisit this for AC3/EAC3 support on AndroidTV
+      return false;
+#endif
+
     case MimeUtil::VP9:
       // VP9 is supported only in KitKat+ (API Level 19).
       return base::android::BuildInfo::GetInstance()->sdk_int() >= 19;
@@ -256,6 +268,11 @@ struct MediaFormatStrict {
 //   avc1.6400xx - H.264 High
 static const char kMP4AudioCodecsExpression[] =
     "mp4a.66,mp4a.67,mp4a.68,mp4a.69,mp4a.6B,mp4a.40.2,mp4a.40.02,mp4a.40.5,"
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+    "ac-3,ec-3,"  // Note: only one variant of eac codec string is sufficient

[ddorwin, 2015/11/25 22:24:08]

Same as the next comment.

[servolk, 2015/12/03 00:56:15]

Done.

+                  // here since these are converted into enums in
+                  // InitializeMimeTypeMaps
+#endif
     "mp4a.40.05,mp4a.40.29";
 static const char kMP4VideoCodecsExpression[] =
     // This is not a complete list of supported avc1 codecs. It is simply used
@@ -271,6 +288,11 @@ static const char kMP4VideoCodecsExpression[] =
     "hev1.1.6.L93.B0,"
 #endif
     "mp4a.66,mp4a.67,mp4a.68,mp4a.69,mp4a.6B,mp4a.40.2,mp4a.40.02,mp4a.40.5,"
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+    "ac-3,ec-3,"  // Note: only one variant of eac codec string is sufficient

[ddorwin, 2015/11/25 22:24:08]

Here and above, be consistent with existing text and start the comment above the
string. Also, perhaps use text more similar to the others?

[servolk, 2015/12/03 00:56:15]

Done.

+                  // here since these are converted into enums in
+                  // InitializeMimeTypeMaps
+#endif
     "mp4a.40.05,mp4a.40.29";
 
 // These containers are also included in
@@ -327,6 +349,14 @@ static const CodecIDMappings kUnambiguousCodecStringMap[] = {
     {"mp4a.40.5", MimeUtil::MPEG4_AAC_SBR_v1},
     {"mp4a.40.05", MimeUtil::MPEG4_AAC_SBR_v1},
     {"mp4a.40.29", MimeUtil::MPEG4_AAC_SBR_PS_v2},
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)
+    {"ac-3", MimeUtil::AC3},
+    {"ec-3", MimeUtil::EAC3},

[ddorwin, 2015/11/25 22:24:07]

group the codecs together

[servolk, 2015/12/03 00:56:15]

Done.

+    {"mp4a.a5", MimeUtil::AC3},
+    {"mp4a.A5", MimeUtil::AC3},

[ddorwin, 2015/11/25 22:24:08]

Why both cases? Is one not "correct?" With everything else case sensitive, this
seems odd.

[servolk, 2015/12/03 00:56:15]

I've copied the comment from the unit test that references crbug.com/564960 to
explain why we need both.

+    {"mp4a.a6", MimeUtil::EAC3},
+    {"mp4a.A6", MimeUtil::EAC3},
+#endif
     {"vorbis", MimeUtil::VORBIS},
     {"opus", MimeUtil::OPUS},
     {"vp8", MimeUtil::VP8},
@@ -696,6 +726,10 @@ bool MimeUtil::IsCodecSupported(Codec codec) const {
 
 bool MimeUtil::IsCodecProprietary(Codec codec) const {
   switch (codec) {
+#if defined(ENABLE_AC3_EAC3_AUDIO_DEMUXING)

[ddorwin, 2015/11/25 22:24:08]

ditto and match order of enum.

[servolk, 2015/12/03 00:56:15]

Done.

+    case AC3:
+    case EAC3:
+#endif
     case INVALID_CODEC:
     case MP3:
     case MPEG2_AAC_LC: