MEDIA_LOG for large encoded timestamp gaps in decoder stream.

media/filters/decoder_stream.h

Index: media/filters/decoder_stream.h
diff --git a/media/filters/decoder_stream.h b/media/filters/decoder_stream.h
index 7e2519ddd1bd7eaec5a64019b694c127b21f5232..1bb707c9b0b39c91997904665045946ccb302999 100644
--- a/media/filters/decoder_stream.h
+++ b/media/filters/decoder_stream.h
@@ -6,6 +6,7 @@
 #define MEDIA_FILTERS_DECODER_STREAM_H_
 
 #include <list>
+#include <memory>
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ -13,6 +14,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "media/base/audio_decoder.h"
+#include "media/base/audio_timestamp_helper.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/media_export.h"
 #include "media/base/media_log.h"
@@ -191,6 +193,13 @@ class MEDIA_EXPORT DecoderStream {
   void ResetDecoder();
   void OnDecoderReset();
 
+  // These methods monitor DecoderBuffer timestamps for gaps for the purpose of
+  // warning developers when gaps may cause AV sync drift. A DecoderBuffer's
+  // timestamp should roughly equal the timestamp of the previous buffer offset
+  // by the previous buffer's duration.
+  void CheckForTimestampGap(const scoped_refptr<DecoderBuffer>& buffer);
+  void RecordOutputDuration(const scoped_refptr<Output>& output);
+
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   scoped_refptr<MediaLog> media_log_;
@@ -206,6 +215,34 @@ class MEDIA_EXPORT DecoderStream {
 
   DemuxerStream* stream_;
 
+  // Stores the timestamp from the DecoderBuffer corresponding to the first
+  // decoded output. See CheckForTimestampGap().
+  base::TimeDelta audio_base_ts_;
+
+  // Initially false, set to true when we observe gap between encoded timestamps
+  // match gap between output decoder buffers.
+  bool stable_audio_times_;
+
+  // Counts attempts to adjust |audio_ts_offset_| while trying to meet
+  // audio timestamp expectations. Give up making adjustments when count exceeds
+  // |kLimitTriesForStableTiming|.
+  int num_unstable_audio_tries_;
+
+  // Initially zero, we adjust the offset as needed for the first few buffers

[DaleCurtis, 2016/05/17 21:32:54]

Am I understanding correctly that this is equivalent to the following:

|last_provided_input_ts_ - first_output_buffer_ts|?

[chcunningham, 2016/05/18 00:18:00]

I would say that, once stable, this is
= last_provided_input_ts - expected_input_ts_based_on_output_frames.

+  // of decoded output to make encoded buffer timestamp gaps line up with
+  // expectations. See implementation of CheckForTimestampGap().
+  base::TimeDelta audio_ts_offset_;
+
+  // Accumulates time as from decoded audio frames. See CheckForTimestampGap().
+  std::unique_ptr<AudioTimestampHelper> audio_output_ts_helper_;
+
+  // How many milliseconds can DecoderBuffer timestamps differ from expectations
+  // before we MEDIA_LOG warn developers. Threshold initially set from
+  // kGapWarningThresholdMsec. Once hit, the threshold is increased by
+  // the detected gap amount. This avoids log spam while still emitting
+  // logs if things get worse. See CheckTimestampForGap().
+  uint32_t drift_warning_threshold_msec_;
+
   std::unique_ptr<DecoderSelector<StreamType>> decoder_selector_;
 
   std::unique_ptr<Decoder> decoder_;