Add FLAC audio codec support

media/base/mime_util_internal.cc

Index: media/base/mime_util_internal.cc
diff --git a/media/base/mime_util_internal.cc b/media/base/mime_util_internal.cc
index 11a763e74ab3c0054e6a39db8a3bcdbac462b19b..70faa9c6043a1e0d61c269279e94425a712937e8 100644
--- a/media/base/mime_util_internal.cc
+++ b/media/base/mime_util_internal.cc
@@ -33,6 +33,7 @@ struct CodecIDMappings {
 // The "mp4a" strings come from RFC 6381.
 static const CodecIDMappings kUnambiguousCodecStringMap[] = {
     {"1", MimeUtil::PCM},  // We only allow this for WAV so it isn't ambiguous.
+    {"flac", MimeUtil::FLAC},

[ddorwin, 2016/11/17 17:46:31]

We don't need this since we aren't currently supporting "flac" as a codec
independent of the FLAC format. See below.

[DaleCurtis, 2016/11/17 23:41:57]

Removed.

     // avc1/avc3.XXXXXX may be unambiguous; handled by ParseAVCCodecId().
     // hev1/hvc1.XXXXXX may be unambiguous; handled by ParseHEVCCodecID().
     // vp9, vp9.0, vp09.xx.xx.xx.xx.xx.xx.xx may be unambiguous; handled by
@@ -366,6 +367,9 @@ void MimeUtil::AddSupportedMediaFormats() {
   CodecSet webm_codecs(webm_audio_codecs);
   webm_codecs.insert(webm_video_codecs.begin(), webm_video_codecs.end());
 
+  CodecSet flac_audio_codecs;

[ddorwin, 2016/11/17 17:46:31]

We don't need this. Instead, update GetDefaultCodecLowerCase.

[DaleCurtis, 2016/11/17 23:41:57]

Removed.

+  flac_audio_codecs.insert(FLAC);
+
 #if defined(USE_PROPRIETARY_CODECS)
   CodecSet mp3_codecs;
   mp3_codecs.insert(MP3);
@@ -409,6 +413,10 @@ void MimeUtil::AddSupportedMediaFormats() {
   // TODO(ddorwin): Should the application type support Opus?
   AddContainerWithCodecs("application/ogg", ogg_codecs, false);
 
+  AddContainerWithCodecs("audio/flac", flac_audio_codecs, false);

[ddorwin, 2016/11/17 17:46:31]

s/flac_audio_codecs/implicit_codec/

We don't want 'audio/flac; codecs=flac'. Instead, we need to treat this like
'audio/mp3'.

[DaleCurtis, 2016/11/17 23:41:57]

Done.

+  AddContainerWithCodecs("audio/x-flac", flac_audio_codecs, false);

[ddorwin, 2016/11/16 17:44:47]

Do we need to support these other variants? Are there many sites using these? x-
variants? Unless there are a lot of legacy uses (seems unlikely given the lack
of browser support), we should try to stick to one. Maybe add UMAs to determine
if we need others.

Firefox claims to only support the first two and prefer the first:
https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats#FLAC
However, the code actually supports all three:
https://dxr.mozilla.org/mozilla-central/source/dom/media/flac/FlacDecoder.cpp

Maybe we should reach out to find out why and coordinate. Let me know if you
need a contact.

For completeness:
* https://xiph.org/flac/ does not appear to mention a type.
* http://www.digitalpreservation.gov/formats/fdd/fdd000198.shtml specifies
"audio/flac"
* "flac" does not appear in
http://www.iana.org/assignments/media-types/media-types.xhtml
* https://en.wikipedia.org/wiki/FLAC#cite_ref-1 says, "Registration being sought
as audio/flac" but provides no reference. That text was added in 2007
(https://en.wikipedia.org/w/index.php?title=FLAC&diff=prev&oldid=164696923).

[ddorwin, 2016/11/17 17:46:31]

FWIW, this would also be inconsistent with net/:
https://cs.chromium.org/chromium/src/net/base/mime_util.cc?q=audio/flac&sq=pa...

[DaleCurtis, 2016/11/17 23:41:58]

Made consistent with net, i.e. just audio/flac

+  AddContainerWithCodecs("application/x-flac", flac_audio_codecs, false);
+
 #if defined(USE_PROPRIETARY_CODECS)
   AddContainerWithCodecs("audio/mpeg", mp3_codecs, true);  // Allow "mp3".
   AddContainerWithCodecs("audio/mp3", implicit_codec, true);
@@ -562,6 +570,7 @@ bool MimeUtil::IsCodecSupportedOnPlatform(
     // The remaining codecs may be supported depending on platform abilities.
     // ----------------------------------------------------------------------
 
+    case FLAC:

[ddorwin, 2016/11/16 17:44:47]

Is this actually supported by MediaPlayer? MediaCodec?

Please try to order consistently with the definition.

[DaleCurtis, 2016/11/17 23:41:57]

Yes, it's supported by Android platform always.

https://developer.android.com/guide/appendix/media-formats.html

     case PCM:
     case MP3:
     case MPEG4_AAC:
@@ -766,6 +775,7 @@ bool MimeUtil::IsCodecProprietary(Codec codec) const {
     case HEVC:
       return true;
 
+    case FLAC:

[ddorwin, 2016/11/17 17:46:31]

FLAC should be added to all the tests in
content/browser/media/media_canplaytype_browsertest.cc.
See "audio/mp3" for examples of codec-less types. But also include tests for
"flac" in the codecs parameter for all other container types.

Also, there was a layout test but it was removed. I don't know how much we care
about that if we have have browser tests.
https://codereview.chromium.org/2028463002/diff/40001/third_party/WebKit/Layo...

     case PCM:
     case VORBIS:
     case OPUS: