The Tor Browser: content/media/AudioChannelFormat.h@44a2da4a2ab2

Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

     2 /* vim:set ts=2 sw=2 sts=2 et cindent: */

     3 /* This Source Code Form is subject to the terms of the Mozilla Public

     4  * License, v. 2.0. If a copy of the MPL was not distributed with this

     5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 #ifndef MOZILLA_AUDIOCHANNELFORMAT_H_

     7 #define MOZILLA_AUDIOCHANNELFORMAT_H_

     9 #include <stdint.h>

    11 #include "nsTArrayForwardDeclare.h"

    13 namespace mozilla {

    15 /*

    16  * This file provides utilities for upmixing and downmixing channels.

    17  *

    18  * The channel layouts, upmixing and downmixing are consistent with the

    19  * Web Audio spec.

    20  *

    21  * Channel layouts for up to 6 channels:

    22  *   mono   { M }

    23  *   stereo { L, R }

    24  *          { L, R, C }

    25  *   quad   { L, R, SL, SR }

    26  *          { L, R, C, SL, SR }

    27  *   5.1    { L, R, C, LFE, SL, SR }

    28  *

    29  * Only 1, 2, 4 and 6 are currently defined in Web Audio.

    30  */

    32 /**

    33  * Return a channel count whose channel layout includes all the channels from

    34  * aChannels1 and aChannels2.

    35  */

    36 uint32_t

    37 GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2);

    39 /**

    40  * Given an array of input channel data, and an output channel count,

    41  * replaces the array with an array of upmixed channels.

    42  * This shuffles the array and may set some channel buffers to aZeroChannel.

    43  * Don't call this with input count >= output count.

    44  * This may return *more* channels than requested. In that case, downmixing

    45  * is required to to get to aOutputChannelCount. (This is how we handle

    46  * odd cases like 3 -> 4 upmixing.)

    47  * If aChannelArray.Length() was the input to one of a series of

    48  * GetAudioChannelsSuperset calls resulting in aOutputChannelCount,

    49  * no downmixing will be required.

    50  */

    51 void

    52 AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,

    53                    uint32_t aOutputChannelCount,

    54                    const void* aZeroChannel);

    56 /**

    57  * Given an array of input channels (which must be float format!),

    58  * downmix to aOutputChannelCount, and copy the results to the

    59  * channel buffers in aOutputChannels.

    60  * Don't call this with input count <= output count.

    61  */

    62 void

    63 AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,

    64                      float** aOutputChannels,

    65                      uint32_t aOutputChannelCount,

    66                      uint32_t aDuration);

    68 // A version of AudioChannelsDownMix that downmixes int16_ts may be required.

    70 } // namespace mozilla

    72 #endif /* MOZILLA_AUDIOCHANNELFORMAT_H_ */

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