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71 lines
2.4 KiB
C++
71 lines
2.4 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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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
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MOZILLA_AUDIOCHANNELFORMAT_H_
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#define MOZILLA_AUDIOCHANNELFORMAT_H_
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#include "nsTArray.h"
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namespace mozilla {
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/*
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* This file provides utilities for upmixing and downmixing channels.
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*
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* The channel layouts, upmixing and downmixing are consistent with the
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* Web Audio spec.
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*
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* Channel layouts for up to 6 channels:
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* mono { M }
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* stereo { L, R }
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* { L, R, C }
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* quad { L, R, SL, SR }
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* { L, R, C, SL, SR }
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* 5.1 { L, R, C, LFE, SL, SR }
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*
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* Only 1, 2, 4 and 6 are currently defined in Web Audio.
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*/
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/**
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* Return a channel count whose channel layout includes all the channels from
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* aChannels1 and aChannels2.
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*/
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uint32_t
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GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2);
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/**
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* Given an array of input channel data, and an output channel count,
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* replaces the array with an array of upmixed channels.
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* This shuffles the array and may set some channel buffers to aZeroChannel.
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* Don't call this with input count >= output count.
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* This may return *more* channels than requested. In that case, downmixing
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* is required to to get to aOutputChannelCount. (This is how we handle
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* odd cases like 3 -> 4 upmixing.)
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* If aChannelArray.Length() was the input to one of a series of
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* GetAudioChannelsSuperset calls resulting in aOutputChannelCount,
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* no downmixing will be required.
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*/
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void
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AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,
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uint32_t aOutputChannelCount,
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const void* aZeroChannel);
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/**
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* Given an array of input channels (which must be float format!),
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* downmix to aOutputChannelCount, and copy the results to the
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* channel buffers in aOutputChannels.
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* Don't call this with input count <= output count.
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*/
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void
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AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,
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float** aOutputChannels,
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uint32_t aOutputChannelCount,
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uint32_t aDuration);
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// A version of AudioChannelsDownMix that downmixes int16_ts may be required.
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} // namespace mozilla
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#endif /* MOZILLA_AUDIOCHANNELFORMAT_H_ */
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