1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/AudioChannelFormat.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,72 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim:set ts=2 sw=2 sts=2 et cindent: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +#ifndef MOZILLA_AUDIOCHANNELFORMAT_H_
1.10 +#define MOZILLA_AUDIOCHANNELFORMAT_H_
1.11 +
1.12 +#include <stdint.h>
1.13 +
1.14 +#include "nsTArrayForwardDeclare.h"
1.15 +
1.16 +namespace mozilla {
1.17 +
1.18 +/*
1.19 + * This file provides utilities for upmixing and downmixing channels.
1.20 + *
1.21 + * The channel layouts, upmixing and downmixing are consistent with the
1.22 + * Web Audio spec.
1.23 + *
1.24 + * Channel layouts for up to 6 channels:
1.25 + * mono { M }
1.26 + * stereo { L, R }
1.27 + * { L, R, C }
1.28 + * quad { L, R, SL, SR }
1.29 + * { L, R, C, SL, SR }
1.30 + * 5.1 { L, R, C, LFE, SL, SR }
1.31 + *
1.32 + * Only 1, 2, 4 and 6 are currently defined in Web Audio.
1.33 + */
1.34 +
1.35 +/**
1.36 + * Return a channel count whose channel layout includes all the channels from
1.37 + * aChannels1 and aChannels2.
1.38 + */
1.39 +uint32_t
1.40 +GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2);
1.41 +
1.42 +/**
1.43 + * Given an array of input channel data, and an output channel count,
1.44 + * replaces the array with an array of upmixed channels.
1.45 + * This shuffles the array and may set some channel buffers to aZeroChannel.
1.46 + * Don't call this with input count >= output count.
1.47 + * This may return *more* channels than requested. In that case, downmixing
1.48 + * is required to to get to aOutputChannelCount. (This is how we handle
1.49 + * odd cases like 3 -> 4 upmixing.)
1.50 + * If aChannelArray.Length() was the input to one of a series of
1.51 + * GetAudioChannelsSuperset calls resulting in aOutputChannelCount,
1.52 + * no downmixing will be required.
1.53 + */
1.54 +void
1.55 +AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,
1.56 + uint32_t aOutputChannelCount,
1.57 + const void* aZeroChannel);
1.58 +
1.59 +/**
1.60 + * Given an array of input channels (which must be float format!),
1.61 + * downmix to aOutputChannelCount, and copy the results to the
1.62 + * channel buffers in aOutputChannels.
1.63 + * Don't call this with input count <= output count.
1.64 + */
1.65 +void
1.66 +AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,
1.67 + float** aOutputChannels,
1.68 + uint32_t aOutputChannelCount,
1.69 + uint32_t aDuration);
1.70 +
1.71 +// A version of AudioChannelsDownMix that downmixes int16_ts may be required.
1.72 +
1.73 +} // namespace mozilla
1.74 +
1.75 +#endif /* MOZILLA_AUDIOCHANNELFORMAT_H_ */
