1 files changed, 81 insertions, 0 deletions
diff --git a/chromium/media/base/audio_discard_helper.h b/chromium/media/base/audio_discard_helper.h
new file mode 100644
index 00000000000..deeb45f37ea
--- /dev/null
+++ b/chromium/media/base/audio_discard_helper.h
@@ -0,0 +1,81 @@
+// Copyright 2014 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_BASE_AUDIO_DISCARD_HELPER_H_
+#define MEDIA_BASE_AUDIO_DISCARD_HELPER_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/time/time.h"
+#include "media/base/audio_timestamp_helper.h"
+#include "media/base/buffers.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class AudioBuffer;
+
+// Helper class for managing timestamps and discard events around decoding.
+class MEDIA_EXPORT AudioDiscardHelper {
+ public:
+  // |sample_rate| is the sample rate of decoded data which will be handed into
+  // the ProcessBuffers() call.
+  //
+  // |decoder_delay| is the number of frames a decoder will output before data
+  // corresponding to the first encoded buffer is output.  Callers only need to
+  // specify this if the decoder inserts frames which have no corresponding
+  // encoded buffer.
+  //
+  // For example, most MP3 decoders will output 529 junk frames before the data
+  // corresponding to the first encoded buffer is output.  These frames are not
+  // represented in the encoded data stream and instead are an artifact of how
+  // most MP3 decoders work.  See http://lame.sourceforge.net/tech-FAQ.txt
+  //
+  // NOTE: End discard is only supported when there is no |decoder_delay|.
+  AudioDiscardHelper(int sample_rate, size_t decoder_delay);
+  ~AudioDiscardHelper();
+
+  // Converts a TimeDelta to a frame count based on the constructed sample rate.
+  // |duration| must be positive.
+  size_t TimeDeltaToFrames(base::TimeDelta duration) const;
+
+  // Resets internal state and indicates that |initial_discard| of upcoming
+  // frames should be discarded.
+  void Reset(size_t initial_discard);
+
+  // Applies discard padding from the encoded buffer along with any initial
+  // discards.  |decoded_buffer| may be NULL, if not the timestamp and duration
+  // will be set after discards are applied.  Returns true if |decoded_buffer|
+  // exists after processing discard events.  Returns false if |decoded_buffer|
+  // was NULL, is completely discarded, or a processing error occurs.
+  //
+  // If AudioDiscardHelper is not initialized() the timestamp of the first
+  // |encoded_buffer| will be used as the basis for all future timestamps set on
+  // |decoded_buffer|s.  If the first buffer has a negative timestamp it will be
+  // clamped to zero.
+  bool ProcessBuffers(const scoped_refptr<DecoderBuffer>& encoded_buffer,
+                      const scoped_refptr<AudioBuffer>& decoded_buffer);
+
+  // Whether any buffers have been processed.
+  bool initialized() const {
+    return timestamp_helper_.base_timestamp() != kNoTimestamp();
+  }
+
+ private:
+  const int sample_rate_;
+  const size_t decoder_delay_;
+  AudioTimestampHelper timestamp_helper_;
+
+  size_t discard_frames_;
+  base::TimeDelta last_input_timestamp_;
+
+  bool delayed_discard_;
+  DecoderBuffer::DiscardPadding delayed_discard_padding_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(AudioDiscardHelper);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_DISCARD_HELPER_H_