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_MULTI_CHANNEL_RESAMPLER_H_ 6 #define MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_ 7 8 #include <vector> 9 10 #include "base/callback.h" 11 #include "base/memory/scoped_ptr.h" 12 #include "base/memory/scoped_vector.h" 13 #include "media/base/sinc_resampler.h" 14 15 namespace media { 16 class AudioBus; 17 18 // MultiChannelResampler is a multi channel wrapper for SincResampler; allowing 19 // high quality sample rate conversion of multiple channels at once. 20 class MEDIA_EXPORT MultiChannelResampler { 21 public: 22 // Callback type for providing more data into the resampler. Expects AudioBus 23 // to be completely filled with data upon return; zero padded if not enough 24 // frames are available to satisfy the request. |frame_delay| is the number 25 // of output frames already processed and can be used to estimate delay. 26 typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB; 27 28 // Constructs a MultiChannelResampler with the specified |read_cb|, which is 29 // used to acquire audio data for resampling. |io_sample_rate_ratio| is the 30 // ratio of input / output sample rates. |request_frames| is the size in 31 // frames of the AudioBus to be filled by |read_cb|. 32 MultiChannelResampler(int channels, 33 double io_sample_rate_ratio, 34 size_t request_frames, 35 const ReadCB& read_cb); 36 virtual ~MultiChannelResampler(); 37 38 // Resamples |frames| of data from |read_cb_| into AudioBus. 39 void Resample(int frames, AudioBus* audio_bus); 40 41 // Flush all buffered data and reset internal indices. Not thread safe, do 42 // not call while Resample() is in progress. 43 void Flush(); 44 45 // Update ratio for all SincResamplers. SetRatio() will cause reconstruction 46 // of the kernels used for resampling. Not thread safe, do not call while 47 // Resample() is in progress. 48 void SetRatio(double io_sample_rate_ratio); 49 50 // The maximum size in frames that guarantees Resample() will only make a 51 // single call to |read_cb_| for more data. 52 int ChunkSize() const; 53 54 private: 55 // SincResampler::ReadCB implementation. ProvideInput() will be called for 56 // each channel (in channel order) as SincResampler needs more data. 57 void ProvideInput(int channel, int frames, float* destination); 58 59 // Source of data for resampling. 60 ReadCB read_cb_; 61 62 // Each channel has its own high quality resampler. 63 ScopedVector<SincResampler> resamplers_; 64 65 // Buffers for audio data going into SincResampler from ReadCB. 66 scoped_ptr<AudioBus> resampler_audio_bus_; 67 68 // To avoid a memcpy() on the first channel we create a wrapped AudioBus where 69 // the first channel points to the |destination| provided to ProvideInput(). 70 scoped_ptr<AudioBus> wrapped_resampler_audio_bus_; 71 72 // The number of output frames that have successfully been processed during 73 // the current Resample() call. 74 int output_frames_ready_; 75 76 DISALLOW_COPY_AND_ASSIGN(MultiChannelResampler); 77 }; 78 79 } // namespace media 80 81 #endif // MEDIA_BASE_MULTI_CHANNEL_RESAMPLER_H_ 82