michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: #ifndef MOZILLA_AUDIOCHANNELFORMAT_H_
michael@0: #define MOZILLA_AUDIOCHANNELFORMAT_H_
michael@0: 
michael@0: #include <stdint.h>
michael@0: 
michael@0: #include "nsTArrayForwardDeclare.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: /*
michael@0:  * This file provides utilities for upmixing and downmixing channels.
michael@0:  *
michael@0:  * The channel layouts, upmixing and downmixing are consistent with the
michael@0:  * Web Audio spec.
michael@0:  *
michael@0:  * Channel layouts for up to 6 channels:
michael@0:  *   mono   { M }
michael@0:  *   stereo { L, R }
michael@0:  *          { L, R, C }
michael@0:  *   quad   { L, R, SL, SR }
michael@0:  *          { L, R, C, SL, SR }
michael@0:  *   5.1    { L, R, C, LFE, SL, SR }
michael@0:  *
michael@0:  * Only 1, 2, 4 and 6 are currently defined in Web Audio.
michael@0:  */
michael@0: 
michael@0: /**
michael@0:  * Return a channel count whose channel layout includes all the channels from
michael@0:  * aChannels1 and aChannels2.
michael@0:  */
michael@0: uint32_t
michael@0: GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2);
michael@0: 
michael@0: /**
michael@0:  * Given an array of input channel data, and an output channel count,
michael@0:  * replaces the array with an array of upmixed channels.
michael@0:  * This shuffles the array and may set some channel buffers to aZeroChannel.
michael@0:  * Don't call this with input count >= output count.
michael@0:  * This may return *more* channels than requested. In that case, downmixing
michael@0:  * is required to to get to aOutputChannelCount. (This is how we handle
michael@0:  * odd cases like 3 -> 4 upmixing.)
michael@0:  * If aChannelArray.Length() was the input to one of a series of
michael@0:  * GetAudioChannelsSuperset calls resulting in aOutputChannelCount,
michael@0:  * no downmixing will be required.
michael@0:  */
michael@0: void
michael@0: AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,
michael@0:                    uint32_t aOutputChannelCount,
michael@0:                    const void* aZeroChannel);
michael@0: 
michael@0: /**
michael@0:  * Given an array of input channels (which must be float format!),
michael@0:  * downmix to aOutputChannelCount, and copy the results to the
michael@0:  * channel buffers in aOutputChannels.
michael@0:  * Don't call this with input count <= output count.
michael@0:  */
michael@0: void
michael@0: AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,
michael@0:                      float** aOutputChannels,
michael@0:                      uint32_t aOutputChannelCount,
michael@0:                      uint32_t aDuration);
michael@0: 
michael@0: // A version of AudioChannelsDownMix that downmixes int16_ts may be required.
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif /* MOZILLA_AUDIOCHANNELFORMAT_H_ */