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// Copyright (c) 2012 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.
#include <vector>
#include "base/callback.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "media/base/sinc_resampler.h"
namespace media {
class AudioBus;
// MultiChannelResampler is a multi channel wrapper for SincResampler; allowing
// high quality sample rate conversion of multiple channels at once.
class MEDIA_EXPORT MultiChannelResampler {
// Callback type for providing more data into the resampler. Expects AudioBus
// to be completely filled with data upon return; zero padded if not enough
// frames are available to satisfy the request. |frame_delay| is the number
// of output frames already processed and can be used to estimate delay.
typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB;
// Constructs a MultiChannelResampler with the specified |read_cb|, which is
// used to acquire audio data for resampling. |io_sample_rate_ratio| is the
// ratio of input / output sample rates. |request_frames| is the size in
// frames of the AudioBus to be filled by |read_cb|.
MultiChannelResampler(int channels,
double io_sample_rate_ratio,
size_t request_frames,
const ReadCB& read_cb);
virtual ~MultiChannelResampler();
// Resamples |frames| of data from |read_cb_| into AudioBus.
void Resample(int frames, AudioBus* audio_bus);
// Flush all buffered data and reset internal indices. Not thread safe, do
// not call while Resample() is in progress.
void Flush();
// Update ratio for all SincResamplers. SetRatio() will cause reconstruction
// of the kernels used for resampling. Not thread safe, do not call while
// Resample() is in progress.
void SetRatio(double io_sample_rate_ratio);
// The maximum size in frames that guarantees Resample() will only make a
// single call to |read_cb_| for more data.
int ChunkSize() const;
// SincResampler::ReadCB implementation. ProvideInput() will be called for
// each channel (in channel order) as SincResampler needs more data.
void ProvideInput(int channel, int frames, float* destination);
// Source of data for resampling.
ReadCB read_cb_;
// Each channel has its own high quality resampler.
ScopedVector<SincResampler> resamplers_;
// Buffers for audio data going into SincResampler from ReadCB.
scoped_ptr<AudioBus> resampler_audio_bus_;
// To avoid a memcpy() on the first channel we create a wrapped AudioBus where
// the first channel points to the |destination| provided to ProvideInput().
scoped_ptr<AudioBus> wrapped_resampler_audio_bus_;
// The number of output frames that have successfully been processed during
// the current Resample() call.
int output_frames_ready_;
} // namespace media