Implemented parsing of HEVC codec ids

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 c86dd6f2611925bd011961023840921416f54470..ac1623dbf5fb78408f58c865c62aca8a6faa8a10 100644
--- a/media/base/mime_util_internal.cc
+++ b/media/base/mime_util_internal.cc
@@ -214,42 +214,6 @@ static bool IsValidH264Level(uint8_t level_idc) {
           (level_idc >= 50 && level_idc <= 51));
 }
 
-#if BUILDFLAG(ENABLE_HEVC_DEMUXING)
-// ISO/IEC FDIS 14496-15 standard section E.3 describes the syntax of codec ids
-// reserved for HEVC. According to that spec HEVC codec id must start with
-// either "hev1." or "hvc1.". We don't yet support full parsing of HEVC codec
-// ids, but since no other codec id starts with those string we'll just treat
-// any string starting with "hev1." or "hvc1." as valid HEVC codec ids.
-// crbug.com/482761
-static bool ParseHEVCCodecID(const std::string& codec_id,
-                             MimeUtil::Codec* codec,
-                             bool* is_ambiguous) {
-  if (base::StartsWith(codec_id, "hev1.", base::CompareCase::SENSITIVE) ||
-      base::StartsWith(codec_id, "hvc1.", base::CompareCase::SENSITIVE)) {
-    *codec = MimeUtil::HEVC_MAIN;
-
-    // TODO(servolk): Full HEVC codec id parsing is not implemented yet (see
-    // crbug.com/482761). So treat HEVC codec ids as ambiguous for now.
-    *is_ambiguous = true;
-
-    // TODO(servolk): Most HEVC codec ids are treated as ambiguous (see above),
-    // but we need to recognize at least one valid unambiguous HEVC codec id,
-    // which is added into kMP4VideoCodecsExpression. We need it to be
-    // unambiguous to avoid DCHECK(!is_ambiguous) in InitializeMimeTypeMaps. We
-    // also use these in unit tests (see
-    // content/browser/media/media_canplaytype_browsertest.cc).
-    // Remove this workaround after crbug.com/482761 is fixed.
-    if (codec_id == "hev1.1.6.L93.B0" || codec_id == "hvc1.1.6.L93.B0") {
-      *is_ambiguous = false;
-    }
-
-    return true;
-  }
-
-  return false;
-}
-#endif
-
 MimeUtil::MimeUtil() : allow_proprietary_codecs_(false) {
 #if defined(OS_ANDROID)
   platform_info_.is_unified_media_pipeline_enabled =
@@ -490,7 +454,7 @@ bool MimeUtil::IsCodecSupportedOnPlatform(
       DCHECK(!is_encrypted || platform_info.has_platform_decoders);
       return true;
 
-    case HEVC_MAIN:
+    case HEVC:
 #if BUILDFLAG(ENABLE_HEVC_DEMUXING)
       if (platform_info.is_unified_media_pipeline_enabled &&
           !platform_info.has_platform_decoders) {
@@ -547,15 +511,17 @@ bool MimeUtil::StringToCodec(const std::string& codec_id,
 // If |codec_id| is not in |string_to_codec_map_|, then we assume that it is
 // either H.264 or HEVC/H.265 codec ID because currently those are the only
 // ones that are not added to the |string_to_codec_map_| and require parsing.
+  VideoCodecProfile profile = VIDEO_CODEC_PROFILE_UNKNOWN;
+  uint8_t level_idc = 0;
 
 #if BUILDFLAG(ENABLE_HEVC_DEMUXING)

[ddorwin, 2016/04/02 00:09:06]

I believe there was a reason this was originally added before AVC, but should we
move it after? (It's also less likely than AVC.)

[servolk, 2016/04/02 00:35:04]

Yes, we used to have 'return ParseH264CodecId' at the end of this function in
the past, so HEVC was inserted above ParseH264. Now that this code looks
differently we can move HEVC below.

-  if (ParseHEVCCodecID(codec_id, codec, is_ambiguous)) {
+  if (ParseHEVCCodecId(codec_id, &profile, &level_idc)) {
+    *is_ambiguous = false;

[ddorwin, 2016/04/02 00:09:06]

This assumes that only supported profiles are returned (at least DCHECK that)
AND that the level is valid. Is the latter a safe assumption?

[servolk, 2016/04/02 00:35:04]

Well, HEVC codec ids contain enough information to be unambiguous, so I've set
it to false here. And yes, there are already a few CHECKs inside
ParseHEVCCodecId function that ensure that returned values are within valid
ranges. The actual issue here is that this is_ambiguous flag is actually used to
decide whether we need to return 'maybe' or 'probably' as CanPlayType result,
but the problem is that we  don't have enough information here to decide that.
We'll need to ask actual platform/decoder whether this combination of
profile/level is supported or not. That part is not implemented yet.

[ddorwin, 2016/04/02 00:56:09]

See above. Ambiguous no longer makes sense, BUT we should prefer "maybe" for
things we are unsure about. In this case, until the platform checking is added.
This should not affect most apps.

This will cause the DCHECK in AddContainerWithCodecs() to fire, but, especially
since we want to eliminate this call there (https://crbug.com/461009), you could
just add "|| codec==HEVC".

[ddorwin, 2016/04/06 01:43:56]

That bug is now fixed, so you don't need to worry about the DCHECK.
https://codereview.chromium.org/1864743002/

[servolk, 2016/04/07 00:59:40]

Done.

+    *codec = MimeUtil::HEVC;
     return true;
   }
 #endif
 
-  VideoCodecProfile profile = VIDEO_CODEC_PROFILE_UNKNOWN;
-  uint8_t level_idc = 0;
   if (ParseAVCCodecId(codec_id, &profile, &level_idc)) {
     *codec = MimeUtil::H264;
     *is_ambiguous =
@@ -593,7 +559,7 @@ bool MimeUtil::IsCodecProprietary(Codec codec) const {
     case MPEG2_AAC:
     case MPEG4_AAC:
     case H264:
-    case HEVC_MAIN:
+    case HEVC:
       return true;
 
     case PCM: