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bug 1220037 pack and unpack Nyquist for MOZ_LIBAV_FFT r=padenot

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BufferComplexMultiply knows nothing about this format and so ends up
corrupting the DC coefficient if packed Nyquists are multiplied.

--HG--
extra : rebase_source : feccac4be8d278dc0be020185065a1a9fa596d9c
This commit is contained in:
Karl Tomlinson 2015-10-30 14:48:08 +13:00
parent 68c055849f
commit f5856e8397
1 changed files with 12 additions and 1 deletions
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13
dom/media/webaudio/FFTBlock.h
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@ -83,6 +83,9 @@ public:
PodCopy(complex.Elements(), aData, mFFTSize);
av_rdft_calc(mAvRDFT, complex.Elements());
PodCopy((FFTSample*)mOutputBuffer.Elements(), complex.Elements(), mFFTSize);
// Recover packed Nyquist.
mOutputBuffer[mFFTSize / 2].r = mOutputBuffer[0].i;
mOutputBuffer[0].i = 0.0f;
#else
#ifdef BUILD_ARM_NEON
if (mozilla::supports_neon()) {
@ -110,6 +113,7 @@ public:
#if defined(MOZ_LIBAV_FFT)
{
PodCopy(aDataOut, (float*)mOutputBuffer.Elements(), mFFTSize);
aDataOut[1] = mOutputBuffer[mFFTSize/2].r; // Packed Nyquist
av_rdft_calc(mAvIRDFT, aDataOut);
// TODO: Once bug 877662 lands, change this to use SSE.
// Even though this function doesn't scale, the libav forward transform
@ -136,10 +140,17 @@ public:
void Multiply(const FFTBlock& aFrame)
{
uint32_t halfSize = mFFTSize / 2;
// DFTs are not packed.
MOZ_ASSERT(mOutputBuffer[0].i == 0);
MOZ_ASSERT(mOutputBuffer[halfSize].i == 0);
MOZ_ASSERT(aFrame.mOutputBuffer[0].i == 0);
MOZ_ASSERT(aFrame.mOutputBuffer[halfSize].i == 0);
BufferComplexMultiply(mOutputBuffer.Elements()->f,
aFrame.mOutputBuffer.Elements()->f,
mOutputBuffer.Elements()->f,
mFFTSize / 2 + 1);
halfSize + 1);
}
// Perform a forward FFT on |aData|, assuming zeros after dataSize samples,