diff options
Diffstat (limited to 'Source/WebCore/platform/audio/AudioBus.cpp')
-rw-r--r-- | Source/WebCore/platform/audio/AudioBus.cpp | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/Source/WebCore/platform/audio/AudioBus.cpp b/Source/WebCore/platform/audio/AudioBus.cpp index dd4746d..6f74471 100644 --- a/Source/WebCore/platform/audio/AudioBus.cpp +++ b/Source/WebCore/platform/audio/AudioBus.cpp @@ -32,6 +32,9 @@ #include "AudioBus.h" +#if !PLATFORM(MAC) +#include "SincResampler.h" +#endif #include "VectorMath.h" #include <algorithm> #include <assert.h> @@ -360,6 +363,90 @@ void AudioBus::sumWithGainFrom(const AudioBus &sourceBus, double* lastMixGain, d processWithGainFrom(sourceBus, lastMixGain, targetGain, true); } +#if !PLATFORM(MAC) +PassOwnPtr<AudioBus> AudioBus::createBySampleRateConverting(AudioBus* sourceBus, bool mixToMono, double newSampleRate) +{ + // sourceBus's sample-rate must be known. + ASSERT(sourceBus && sourceBus->sampleRate()); + if (!sourceBus || !sourceBus->sampleRate()) + return 0; + + double sourceSampleRate = sourceBus->sampleRate(); + double destinationSampleRate = newSampleRate; + unsigned numberOfSourceChannels = sourceBus->numberOfChannels(); + + if (numberOfSourceChannels == 1) + mixToMono = false; // already mono + + if (sourceSampleRate == destinationSampleRate) { + // No sample-rate conversion is necessary. + if (mixToMono) + return AudioBus::createByMixingToMono(sourceBus); + + // Return exact copy. + return AudioBus::createBufferFromRange(sourceBus, 0, sourceBus->length()); + } + + // First, mix to mono (if necessary) then sample-rate convert. + AudioBus* resamplerSourceBus; + OwnPtr<AudioBus> mixedMonoBus; + if (mixToMono) { + mixedMonoBus = AudioBus::createByMixingToMono(sourceBus); + resamplerSourceBus = mixedMonoBus.get(); + } else { + // Directly resample without down-mixing. + resamplerSourceBus = sourceBus; + } + + // Calculate destination length based on the sample-rates. + double sampleRateRatio = sourceSampleRate / destinationSampleRate; + int sourceLength = resamplerSourceBus->length(); + int destinationLength = sourceLength / sampleRateRatio; + + // Create destination bus with same number of channels. + unsigned numberOfDestinationChannels = resamplerSourceBus->numberOfChannels(); + OwnPtr<AudioBus> destinationBus(adoptPtr(new AudioBus(numberOfDestinationChannels, destinationLength))); + + // Sample-rate convert each channel. + for (unsigned i = 0; i < numberOfDestinationChannels; ++i) { + float* source = resamplerSourceBus->channel(i)->data(); + float* destination = destinationBus->channel(i)->data(); + + SincResampler resampler(sampleRateRatio); + resampler.process(source, destination, sourceLength); + } + + return destinationBus.release(); +} +#endif // !PLATFORM(MAC) + +PassOwnPtr<AudioBus> AudioBus::createByMixingToMono(AudioBus* sourceBus) +{ + switch (sourceBus->numberOfChannels()) { + case 1: + // Simply create an exact copy. + return AudioBus::createBufferFromRange(sourceBus, 0, sourceBus->length()); + case 2: + { + unsigned n = sourceBus->length(); + OwnPtr<AudioBus> destinationBus(adoptPtr(new AudioBus(1, n))); + + float* sourceL = sourceBus->channel(0)->data(); + float* sourceR = sourceBus->channel(1)->data(); + float* destination = destinationBus->channel(0)->data(); + + // Do the mono mixdown. + for (unsigned i = 0; i < n; ++i) + destination[i] = 0.5 * (sourceL[i] + sourceR[i]); + + return destinationBus.release(); + } + } + + ASSERT_NOT_REACHED(); + return 0; +} + } // WebCore #endif // ENABLE(WEB_AUDIO) |