1 // Copyright (c) 2012 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_PULL_FIFO_H_ 6 #define MEDIA_BASE_AUDIO_PULL_FIFO_H_ 7 8 #include "base/callback.h" 9 #include "media/base/media_export.h" 10 11 namespace media { 12 class AudioBus; 13 14 // A FIFO (First In First Out) buffer to handle mismatches in buffer sizes 15 // between a producer and consumer. The consumer will pull data from this FIFO. 16 // If data is already available in the FIFO, it is provided to the consumer. 17 // If insufficient data is available to satisfy the request, the FIFO will ask 18 // the producer for more data to fulfill a request. 19 class MEDIA_EXPORT AudioPullFifo { 20 public: 21 // Callback type for providing more data into the FIFO. Expects AudioBus 22 // to be completely filled with data upon return; zero padded if not enough 23 // frames are available to satisfy the request. |frame_delay| is the number 24 // of output frames already processed and can be used to estimate delay. 25 typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB; 26 27 // Constructs an AudioPullFifo with the specified |read_cb|, which is used to 28 // read audio data to the FIFO if data is not already available. The internal 29 // FIFO can contain |channel| number of channels, where each channel is of 30 // length |frames| audio frames. 31 AudioPullFifo(int channels, int frames, const ReadCB& read_cb); 32 virtual ~AudioPullFifo(); 33 34 // Consumes |frames_to_consume| audio frames from the FIFO and copies 35 // them to |destination|. If the FIFO does not have enough data, we ask 36 // the producer to give us more data to fulfill the request using the 37 // ReadCB implementation. 38 void Consume(AudioBus* destination, int frames_to_consume); 39 40 // Empties the FIFO without deallocating any memory. 41 void Clear(); 42 43 private: 44 // Attempt to fulfill the request using what is available in the FIFO. 45 // Append new data to the |destination| starting at |write_pos|. 46 int ReadFromFifo(AudioBus* destination, int frames_to_provide, int write_pos); 47 48 // Source of data to the FIFO. 49 const ReadCB read_cb_; 50 51 // Temporary audio bus to hold the data from the producer. 52 scoped_ptr<AudioBus> fifo_; 53 int fifo_index_; 54 55 DISALLOW_COPY_AND_ASSIGN(AudioPullFifo); 56 }; 57 58 } // namespace media 59 60 #endif // MEDIA_BASE_AUDIO_PULL_FIFO_H_ 61
