Parsing of encoded duration for unencrypted opus streams.

media/formats/webm/webm_cluster_parser.h

Index: media/formats/webm/webm_cluster_parser.h
diff --git a/media/formats/webm/webm_cluster_parser.h b/media/formats/webm/webm_cluster_parser.h
index 2af102eaa0ce58b28909a6aa15fffd1bdbe4ed00..a6466056e63fa0a5e0ad88b511dd4a37b1ca567c 100644
--- a/media/formats/webm/webm_cluster_parser.h
+++ b/media/formats/webm/webm_cluster_parser.h
@@ -11,6 +11,7 @@
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
+#include "media/base/audio_decoder_config.h"
 #include "media/base/media_export.h"
 #include "media/base/media_log.h"
 #include "media/base/stream_parser.h"
@@ -28,13 +29,17 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
 
   // Arbitrarily-chosen numbers to estimate the duration of a buffer if none is
   // set and there is not enough information to get a better estimate.
-  // TODO(wolenetz/acolwell): Parse audio codebook to determine missing audio
-  // frame durations. See http://crbug.com/351166.
   enum {
     kDefaultAudioBufferDurationInMs = 23,  // Common 1k samples @44.1kHz
     kDefaultVideoBufferDurationInMs = 42  // Low 24fps to reduce stalls
   };
 
+  // Opus packets encode the duration and other parameters in the 5 most
+  // significant bits of the first byte. The index in this array corresponds
+  // to the duration of each frame of the packet in microseconds. See
+  // http://goo.gl/2RmoxA

[wolenetz, 2015/02/03 22:47:02]

I was wrong. Using full URL is more common. Also lets readers see real target
before/without loading it. s/full/shortened/ URL here and in .h please.

[chcunningham, 2015/02/05 02:48:22]

Done.

+  static const uint16 kOpusFrameDurationsMu[];

[wolenetz, 2015/02/03 22:47:02]

_t

[chcunningham, 2015/02/05 02:48:22]

Done.

+
  private:
   // Helper class that manages per-track state.
   class Track {
@@ -143,6 +148,7 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
                     const std::set<int64>& ignored_tracks,
                     const std::string& audio_encryption_key_id,
                     const std::string& video_encryption_key_id,
+                    const AudioCodec audio_codec_,
                     const LogCB& log_cb);
   ~WebMClusterParser() override;
 
@@ -227,11 +233,24 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
   // if that track num is not a text track.
   Track* FindTextTrack(int track_num);
 
+  // Attempts to read the duration from the encoded audio data. This obviously
+  // violates layering rules, but is useful for MSE to know duration in cases
+  // where it isn't explicitly given and cannot be calculated for Blocks at the
+  // end of a Cluster (the next Cluster in playback-order may not be the next
+  // Cluster we parse, so we can't simply use the delta of the first Block in
+  // the next Cluster). Avoid calling if encrypted; may produce unexpected
+  // output. See implementation for supported codecs.

[wolenetz, 2015/02/03 22:47:02]

nit: though private, would be nice to have retval documented here.

[chcunningham, 2015/02/05 02:48:22]

Done.

+  base::TimeDelta TryGetEncodedAudioDuration(const uint8* data, int size);

[wolenetz, 2015/02/03 22:47:02]

nit: const method?

[chcunningham, 2015/02/05 02:48:22]

We chatted. The MEDIA_LOGS break const-ness :(

[wolenetz, 2015/02/05 23:04:59]

Acknowledged.

+
+  // Reads Opus packet header to determine packet duration.

[wolenetz, 2015/02/03 22:47:02]

nit: ditto retval documentation

[chcunningham, 2015/02/05 02:48:22]

Done.

+  base::TimeDelta ReadOpusDuration(const uint8* data, int size);

[wolenetz, 2015/02/03 22:47:02]

nit: const method?

[chcunningham, 2015/02/05 02:48:22]

Same issue with MEDIA_LOG

[wolenetz, 2015/02/05 23:04:59]

Acknowledged.

+
   double timecode_multiplier_;  // Multiplier used to convert timecodes into
                                 // microseconds.
   std::set<int64> ignored_tracks_;
   std::string audio_encryption_key_id_;
   std::string video_encryption_key_id_;
+  const AudioCodec audio_codec_;
 
   WebMListParser parser_;