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-rw-r--r--dom/media/AudioCompactor.h128
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+#if !defined(AudioCompactor_h)
+# define AudioCompactor_h
+
+# include "MediaQueue.h"
+# include "MediaData.h"
+# include "VideoUtils.h"
+
+namespace mozilla {
+
+class AudioCompactor {
+ public:
+ explicit AudioCompactor(MediaQueue<AudioData>& aQueue) : mQueue(aQueue) {
+ // Determine padding size used by AlignedBuffer.
+ size_t paddedSize = AlignedAudioBuffer::AlignmentPaddingSize();
+ mSamplesPadding = paddedSize / sizeof(AudioDataValue);
+ if (mSamplesPadding * sizeof(AudioDataValue) < paddedSize) {
+ // Round up.
+ mSamplesPadding++;
+ }
+ }
+
+ // Push audio data into the underlying queue with minimal heap allocation
+ // slop. This method is responsible for allocating AudioDataValue[] buffers.
+ // The caller must provide a functor to copy the data into the buffers. The
+ // functor must provide the following signature:
+ //
+ // uint32_t operator()(AudioDataValue *aBuffer, uint32_t aSamples);
+ //
+ // The functor must copy as many complete frames as possible to the provided
+ // buffer given its length (in AudioDataValue elements). The number of frames
+ // copied must be returned. This copy functor must support being called
+ // multiple times in order to copy the audio data fully. The copy functor
+ // must copy full frames as partial frames will be ignored.
+ template <typename CopyFunc>
+ bool Push(int64_t aOffset, int64_t aTime, int32_t aSampleRate,
+ uint32_t aFrames, uint32_t aChannels, CopyFunc aCopyFunc) {
+ auto time = media::TimeUnit::FromMicroseconds(aTime);
+
+ // If we are losing more than a reasonable amount to padding, try to chunk
+ // the data.
+ size_t maxSlop = AudioDataSize(aFrames, aChannels) / MAX_SLOP_DIVISOR;
+
+ while (aFrames > 0) {
+ uint32_t samples = GetChunkSamples(aFrames, aChannels, maxSlop);
+ if (samples / aChannels > mSamplesPadding / aChannels + 1) {
+ samples -= mSamplesPadding;
+ }
+ AlignedAudioBuffer buffer(samples);
+ if (!buffer) {
+ return false;
+ }
+
+ // Copy audio data to buffer using caller-provided functor.
+ uint32_t framesCopied = aCopyFunc(buffer.get(), samples);
+
+ NS_ASSERTION(framesCopied <= aFrames, "functor copied too many frames");
+ buffer.SetLength(size_t(framesCopied) * aChannels);
+
+ auto duration = media::TimeUnit(framesCopied, aSampleRate);
+ if (!duration.IsValid()) {
+ return false;
+ }
+
+ RefPtr<AudioData> data = new AudioData(aOffset, time, std::move(buffer),
+ aChannels, aSampleRate);
+ MOZ_DIAGNOSTIC_ASSERT(duration == data->mDuration, "must be equal");
+ mQueue.Push(data);
+
+ // Remove the frames we just pushed into the queue and loop if there is
+ // more to be done.
+ time += duration;
+ aFrames -= framesCopied;
+
+ // NOTE: No need to update aOffset as its only an approximation anyway.
+ }
+
+ return true;
+ }
+
+ // Copy functor suitable for copying audio samples already in the
+ // AudioDataValue format/layout expected by AudioStream on this platform.
+ class NativeCopy {
+ public:
+ NativeCopy(const uint8_t* aSource, size_t aSourceBytes, uint32_t aChannels)
+ : mSource(aSource),
+ mSourceBytes(aSourceBytes),
+ mChannels(aChannels),
+ mNextByte(0) {}
+
+ uint32_t operator()(AudioDataValue* aBuffer, uint32_t aSamples);
+
+ private:
+ const uint8_t* const mSource;
+ const size_t mSourceBytes;
+ const uint32_t mChannels;
+ size_t mNextByte;
+ };
+
+ // Allow 12.5% slop before chunking kicks in. Public so that the gtest can
+ // access it.
+ static const size_t MAX_SLOP_DIVISOR = 8;
+
+ private:
+ // Compute the number of AudioDataValue samples that will be fit the most
+ // frames while keeping heap allocation slop less than the given threshold.
+ static uint32_t GetChunkSamples(uint32_t aFrames, uint32_t aChannels,
+ size_t aMaxSlop);
+
+ static size_t BytesPerFrame(uint32_t aChannels) {
+ return sizeof(AudioDataValue) * aChannels;
+ }
+
+ static size_t AudioDataSize(uint32_t aFrames, uint32_t aChannels) {
+ return aFrames * BytesPerFrame(aChannels);
+ }
+
+ MediaQueue<AudioData>& mQueue;
+ size_t mSamplesPadding;
+};
+
+} // namespace mozilla
+
+#endif // AudioCompactor_h