The Tor Browser: content/media/AudioChannelFormat.cpp@44a2da4a2ab2 (annotated)

content/media/AudioChannelFormat.cpp@44a2da4a2ab2 (annotated)

content/media/AudioChannelFormat.cpp

Fri, 16 Jan 2015 04:50:19 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 04:50:19 +0100
branch: TOR_BUG_9701
changeset 13: 44a2da4a2ab2
permissions: -rw-r--r--

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

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "AudioChannelFormat.h"
 #include "nsTArray.h"
 #include <algorithm>
 namespace mozilla {
 enum {
   SURROUND_L,
   SURROUND_R,
   SURROUND_C,
   SURROUND_LFE,
   SURROUND_SL,
   SURROUND_SR
 };
 static const uint32_t CUSTOM_CHANNEL_LAYOUTS = 6;
 static const int IGNORE = CUSTOM_CHANNEL_LAYOUTS;
 static const float IGNORE_F = 0.0f;
 uint32_t
 GetAudioChannelsSuperset(uint32_t aChannels1, uint32_t aChannels2)
 {
   return std::max(aChannels1, aChannels2);
 }
 /**
  * UpMixMatrix represents a conversion matrix by exploiting the fact that
  * each output channel comes from at most one input channel.
  */
 struct UpMixMatrix {
   uint8_t mInputDestination[CUSTOM_CHANNEL_LAYOUTS];
 };
 static const UpMixMatrix
 gUpMixMatrices[CUSTOM_CHANNEL_LAYOUTS*(CUSTOM_CHANNEL_LAYOUTS - 1)/2] =
 {
   // Upmixes from mono
   { { 0, 0 } },
   { { 0, IGNORE, IGNORE } },
   { { 0, 0, IGNORE, IGNORE } },
   { { 0, IGNORE, IGNORE, IGNORE, IGNORE } },
   { { IGNORE, IGNORE, 0, IGNORE, IGNORE, IGNORE } },
   // Upmixes from stereo
   { { 0, 1, IGNORE } },
   { { 0, 1, IGNORE, IGNORE } },
   { { 0, 1, IGNORE, IGNORE, IGNORE } },
   { { 0, 1, IGNORE, IGNORE, IGNORE, IGNORE } },
   // Upmixes from 3-channel
   { { 0, 1, 2, IGNORE } },
   { { 0, 1, 2, IGNORE, IGNORE } },
   { { 0, 1, 2, IGNORE, IGNORE, IGNORE } },
   // Upmixes from quad
   { { 0, 1, 2, 3, IGNORE } },
   { { 0, 1, IGNORE, IGNORE, 2, 3 } },
   // Upmixes from 5-channel
   { { 0, 1, 2, 3, 4, IGNORE } }
 };
 static const int gMixingMatrixIndexByChannels[CUSTOM_CHANNEL_LAYOUTS - 1] =
   { 0, 5, 9, 12, 14 };
 void
 AudioChannelsUpMix(nsTArray<const void*>* aChannelArray,
                    uint32_t aOutputChannelCount,
                    const void* aZeroChannel)
 {
   uint32_t inputChannelCount = aChannelArray->Length();
   uint32_t outputChannelCount =
     GetAudioChannelsSuperset(aOutputChannelCount, inputChannelCount);
   NS_ASSERTION(outputChannelCount > inputChannelCount,
                "No up-mix needed");
   NS_ASSERTION(inputChannelCount > 0, "Bad number of channels");
   NS_ASSERTION(outputChannelCount > 0, "Bad number of channels");
   aChannelArray->SetLength(outputChannelCount);
   if (inputChannelCount < CUSTOM_CHANNEL_LAYOUTS &&
       outputChannelCount <= CUSTOM_CHANNEL_LAYOUTS) {
     const UpMixMatrix& m = gUpMixMatrices[
       gMixingMatrixIndexByChannels[inputChannelCount - 1] +
       outputChannelCount - inputChannelCount - 1];
     const void* outputChannels[CUSTOM_CHANNEL_LAYOUTS];
     for (uint32_t i = 0; i < outputChannelCount; ++i) {
       uint8_t channelIndex = m.mInputDestination[i];
       if (channelIndex == IGNORE) {
         outputChannels[i] = aZeroChannel;
       } else {
         outputChannels[i] = aChannelArray->ElementAt(channelIndex);
       }
     }
     for (uint32_t i = 0; i < outputChannelCount; ++i) {
       aChannelArray->ElementAt(i) = outputChannels[i];
     }
     return;
   }
   for (uint32_t i = inputChannelCount; i < outputChannelCount; ++i) {
     aChannelArray->ElementAt(i) = aZeroChannel;
   }
 }
 /**
  * DownMixMatrix represents a conversion matrix efficiently by exploiting the
  * fact that each input channel contributes to at most one output channel,
  * except possibly for the C input channel in layouts that have one. Also,
  * every input channel is multiplied by the same coefficient for every output
  * channel it contributes to.
  */
 struct DownMixMatrix {
   // Every input channel c is copied to output channel mInputDestination[c]
   // after multiplying by mInputCoefficient[c].
   uint8_t mInputDestination[CUSTOM_CHANNEL_LAYOUTS];
   // If not IGNORE, then the C channel is copied to this output channel after
   // multiplying by its coefficient.
   uint8_t mCExtraDestination;
   float mInputCoefficient[CUSTOM_CHANNEL_LAYOUTS];
 };
 static const DownMixMatrix
 gDownMixMatrices[CUSTOM_CHANNEL_LAYOUTS*(CUSTOM_CHANNEL_LAYOUTS - 1)/2] =
 {
   // Downmixes to mono
   { { 0, 0 }, IGNORE, { 0.5f, 0.5f } },
   { { 0, IGNORE, IGNORE }, IGNORE, { 1.0f, IGNORE_F, IGNORE_F } },
   { { 0, 0, 0, 0 }, IGNORE, { 0.25f, 0.25f, 0.25f, 0.25f } },
   { { 0, IGNORE, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, IGNORE_F, IGNORE_F, IGNORE_F, IGNORE_F } },
   { { 0, 0, 0, IGNORE, 0, 0 }, IGNORE, { 0.7071f, 0.7071f, 1.0f, IGNORE_F, 0.5f, 0.5f } },
   // Downmixes to stereo
   { { 0, 1, IGNORE }, IGNORE, { 1.0f, 1.0f, IGNORE_F } },
   { { 0, 1, 0, 1 }, IGNORE, { 0.5f, 0.5f, 0.5f, 0.5f } },
   { { 0, 1, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, IGNORE_F, IGNORE_F, IGNORE_F } },
   { { 0, 1, 0, IGNORE, 0, 1 }, 1, { 1.0f, 1.0f, 0.7071f, IGNORE_F, 0.7071f, 0.7071f } },
   // Downmixes to 3-channel
   { { 0, 1, 2, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F } },
   { { 0, 1, 2, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F, IGNORE_F } },
   { { 0, 1, 2, IGNORE, IGNORE, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, IGNORE_F, IGNORE_F, IGNORE_F } },
   // Downmixes to quad
   { { 0, 1, 2, 3, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, 1.0f, IGNORE_F } },
   { { 0, 1, 0, IGNORE, 2, 3 }, 1, { 1.0f, 1.0f, 0.7071f, IGNORE_F, 1.0f, 1.0f } },
   // Downmixes to 5-channel
   { { 0, 1, 2, 3, 4, IGNORE }, IGNORE, { 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, IGNORE_F } }
 };
 void
 AudioChannelsDownMix(const nsTArray<const void*>& aChannelArray,
                      float** aOutputChannels,
                      uint32_t aOutputChannelCount,
                      uint32_t aDuration)
 {
   uint32_t inputChannelCount = aChannelArray.Length();
   const void* const* inputChannels = aChannelArray.Elements();
   NS_ASSERTION(inputChannelCount > aOutputChannelCount, "Nothing to do");
   if (inputChannelCount > 6) {
     // Just drop the unknown channels.
     for (uint32_t o = 0; o < aOutputChannelCount; ++o) {
       memcpy(aOutputChannels[o], inputChannels[o], aDuration*sizeof(float));
     }
     return;
   }
   // Ignore unknown channels, they're just dropped.
   inputChannelCount = std::min<uint32_t>(6, inputChannelCount);
   const DownMixMatrix& m = gDownMixMatrices[
     gMixingMatrixIndexByChannels[aOutputChannelCount - 1] +
     inputChannelCount - aOutputChannelCount - 1];
   // This is slow, but general. We can define custom code for special
   // cases later.
   for (uint32_t s = 0; s < aDuration; ++s) {
     // Reserve an extra junk channel at the end for the cases where we
     // want an input channel to contribute to nothing
     float outputChannels[CUSTOM_CHANNEL_LAYOUTS + 1];
     memset(outputChannels, 0, sizeof(float)*(CUSTOM_CHANNEL_LAYOUTS));
     for (uint32_t c = 0; c < inputChannelCount; ++c) {
       outputChannels[m.mInputDestination[c]] +=
         m.mInputCoefficient[c]*(static_cast<const float*>(inputChannels[c]))[s];
     }
     // Utilize the fact that in every layout, C is the third channel.
     if (m.mCExtraDestination != IGNORE) {
       outputChannels[m.mCExtraDestination] +=
         m.mInputCoefficient[SURROUND_C]*(static_cast<const float*>(inputChannels[SURROUND_C]))[s];
     }
     for (uint32_t c = 0; c < aOutputChannelCount; ++c) {
       aOutputChannels[c][s] = outputChannels[c];
     }
   }
 }
 }

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content/media/AudioChannelFormat.cpp@44a2da4a2ab2 (annotated)

content/media/AudioChannelFormat.cpp