98 lines
3.8 KiB
C++
98 lines
3.8 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef DOM_MEDIA_DRIFTCONTROL_AUDIORESAMPLER_H_
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#define DOM_MEDIA_DRIFTCONTROL_AUDIORESAMPLER_H_
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#include "AudioChunkList.h"
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#include "AudioSegment.h"
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#include "DynamicResampler.h"
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namespace mozilla {
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/**
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* Audio Resampler is a resampler able to change the input rate and channels
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* count on the fly. The API is simple and it is based in AudioSegment in order
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* to be used MTG. Memory allocations, for input and output buffers, will happen
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* in the constructor, when channel count changes and if the amount of input
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* data outgrows the input buffer. The memory is recycled in order to avoid
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* reallocations. It also supports prebuffering of silence. It consists of
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* DynamicResampler and AudioChunkList so please read their documentation if you
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* are interested in more details.
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*
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* The output buffer is preallocated and returned in the form of AudioSegment.
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* The intention is to be used directly in a MediaTrack. Since an AudioChunk
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* must no be "shared" in order to be written, the AudioSegment returned by
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* resampler method must be cleaned up in order to be able for the `AudioChunk`s
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* that it consists of to be reused. For `MediaTrack::mSegment` this happens
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* every ~50ms (look at MediaTrack::AdvanceTimeVaryingValuesToCurrentTime). Thus
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* memory capacity of 100ms has been preallocated for internal input and output
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* buffering. Note that the amount of memory used for input buffering may
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* increase if needed.
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*/
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class AudioResampler final {
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public:
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AudioResampler(uint32_t aInRate, uint32_t aOutRate,
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uint32_t aInputPreBufferFrameCount,
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const PrincipalHandle& aPrincipalHandle);
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/**
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* Append input data into the resampler internal buffer. Copy/move of the
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* memory is taking place. Also, the channel count will change according to
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* the channel count of the chunks.
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*/
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void AppendInput(const AudioSegment& aInSegment);
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/**
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* Get the number of frames that the internal input buffer can hold.
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*/
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uint32_t InputCapacityFrames() const;
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/**
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* Get the number of frames that can be read from the internal input buffer
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* before it becomes empty.
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*/
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uint32_t InputReadableFrames() const;
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/*
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* Reguest `aOutFrames` of audio in the output sample rate. The internal
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* buffered input is used. If the input buffer does not have enough data to
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* reach `aOutFrames` frames, the input buffer is padded with enough silence
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* to allow the requested frames to be resampled and returned, and the
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* pre-buffer is reset so that the next call will be treated as the first.
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*
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* On first call, prepends the internal buffer with silence so that after
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* resampling aOutFrames frames of data, the internal buffer holds input
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* data as close as possible to the configured pre-buffer size.
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*/
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AudioSegment Resample(uint32_t aOutFrames, bool* aHasUnderrun);
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/*
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* Updates the input rate that will be used by the resampler.
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*/
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void UpdateInRate(uint32_t aInRate) {
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Update(aInRate, mResampler.GetChannels());
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}
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/**
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* Set the number of frames that should be used for input pre-buffering.
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*/
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void SetInputPreBufferFrameCount(uint32_t aInputPreBufferFrameCount) {
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mResampler.SetInputPreBufferFrameCount(aInputPreBufferFrameCount);
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}
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private:
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void UpdateChannels(uint32_t aChannels) {
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Update(mResampler.GetInRate(), aChannels);
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}
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void Update(uint32_t aInRate, uint32_t aChannels);
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private:
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DynamicResampler mResampler;
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AudioChunkList mOutputChunks;
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bool mIsSampleFormatSet = false;
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};
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} // namespace mozilla
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#endif // DOM_MEDIA_DRIFTCONTROL_AUDIORESAMPLER_H_
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