MEDIA_LOG for large encoded timestamp gaps in decoder stream.

media/filters/audio_timestamp_validator.h

Index: media/filters/audio_timestamp_validator.h
diff --git a/media/filters/audio_timestamp_validator.h b/media/filters/audio_timestamp_validator.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_
+#define MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/time/time.h"
+#include "media/base/audio_buffer.h"
+#include "media/base/audio_decoder_config.h"
+#include "media/base/audio_timestamp_helper.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/media_log.h"
+#include "media/base/timestamp_constants.h"
+
+namespace media {
+
+class MEDIA_EXPORT AudioTimestampValidator {
+ public:
+  AudioTimestampValidator(const AudioDecoderConfig& decoder_config,
+                          const scoped_refptr<MediaLog>& media_log);
+  ~AudioTimestampValidator();
+
+  // 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<AudioBuffer>& buffer);
+
+ private:
+  bool has_codec_delay_;
+  scoped_refptr<MediaLog> media_log_;
+
+  // Accumulates time from decoded audio frames. We adjust the base timestamp as
+  // needed for the first few buffers (stabilization period) of decoded output
+  // to account for pre-skip and codec delay. See CheckForTimestampGap().
+  std::unique_ptr<AudioTimestampHelper> audio_output_ts_helper_;
+
+  base::TimeDelta audio_base_ts_;
+
+  // Initially false, set to true when we observe gap between encoded timestamps
+  // match gap between output decoder buffers.
+  bool reached_stable_state_;
+
+  // Counts attempts to adjust |audio_output_ts_helper_| base offset in effort
+  // to form expectation for encoded timestamps based on decoded output. Give up
+  // making adjustments when count exceeds |limit_unstable_audio_tries_|.
+  int num_unstable_audio_tries_;
+
+  // Limits the number of attempts to stabilize audio timestamp expectations.
+  int limit_unstable_audio_tries_;
+
+  // 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_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioTimestampValidator);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_AUDIO_TIMESTAMP_VALIDATOR_H_