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| 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef MEDIA_BASE_AUDIO_RECHUNKER_H_ |
| 6 #define MEDIA_BASE_AUDIO_RECHUNKER_H_ |
| 7 |
| 8 #include "base/callback.h" |
| 9 #include "base/macros.h" |
| 10 #include "base/memory/scoped_ptr.h" |
| 11 #include "base/time/time.h" |
| 12 #include "media/base/audio_bus.h" |
| 13 #include "media/base/media_export.h" |
| 14 |
| 15 namespace media { |
| 16 |
| 17 // Yet another FIFO for audio data that re-chunks audio to a desired buffer |
| 18 // size. Unlike AudioFifo and AudioBlockFifo, this FIFO cannot overflow: The |
| 19 // client is required to provide a callback that is called synchronously during |
| 20 // a push whenever enough data becomes available. In addition, this FIFO |
| 21 // shifts reference timestamps to account for any samples that were pending in |
| 22 // internal buffers from prior pushes. This implementation eliminates redundant |
| 23 // memory copies when the input buffer size always matches the desired buffer |
| 24 // size. |
| 25 class MEDIA_EXPORT AudioRechunker final { |
| 26 public: |
| 27 using RechunkedAudioCallback = |
| 28 base::Callback<void(const AudioBus& output, |
| 29 base::TimeDelta reference_timestamp)>; |
| 30 |
| 31 // Creates a new AudioRechunker that re-chunks audio into the required |
| 32 // |output_duration| and delivers it by running |callback|. |
| 33 AudioRechunker(base::TimeDelta output_duration, |
| 34 const RechunkedAudioCallback& callback); |
| 35 |
| 36 ~AudioRechunker(); |
| 37 |
| 38 int sample_rate() const { return sample_rate_; } |
| 39 |
| 40 // Returns the number of frames in each AudioBus delivered to the |
| 41 // RechunkedAudioCallback. |
| 42 int output_frames() const { return output_frames_; } |
| 43 |
| 44 // Must be called at least once before the first call to Push(). May be |
| 45 // called later just before each audio format change. Returns true if it is |
| 46 // possible to EXACTLY re-chunk audio to the required |output_duration| |
| 47 // provided to the constructor, false otherwise (e.g., 22050 Hz audio cannot |
| 48 // be divided evenly into 10 ms chunks). |
| 49 bool SetSampleRate(int sample_rate); |
| 50 |
| 51 // Pushes all audio channel data from |input_bus| through the FIFO. This will |
| 52 // result in zero, one, or multiple synchronous calls to the |
| 53 // RechunkedAudioCallback provided in the constructor. |
| 54 void Push(const AudioBus& input_bus, base::TimeDelta reference_timestamp); |
| 55 |
| 56 private: |
| 57 const base::TimeDelta output_duration_; |
| 58 const RechunkedAudioCallback callback_; |
| 59 |
| 60 // These are computed in each call to SetSampleRate(). |
| 61 int sample_rate_; |
| 62 int output_frames_; |
| 63 |
| 64 // Queue of frames pending for delivery. |
| 65 scoped_ptr<AudioBus> audio_queue_; |
| 66 int pending_frames_; |
| 67 |
| 68 DISALLOW_COPY_AND_ASSIGN(AudioRechunker); |
| 69 }; |
| 70 |
| 71 } // namespace media |
| 72 |
| 73 #endif // MEDIA_BASE_AUDIO_RECHUNKER_H_ |
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