gecko-dev/content/media/AudioSegment.h

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/* -*- 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/. */
#ifndef MOZILLA_AUDIOSEGMENT_H_
#define MOZILLA_AUDIOSEGMENT_H_
#include "MediaSegment.h"
#include "nsISupportsImpl.h"
#include "AudioSampleFormat.h"
#include "SharedBuffer.h"
namespace mozilla {
class AudioStream;
/**
* For auto-arrays etc, guess this as the common number of channels.
*/
const int GUESS_AUDIO_CHANNELS = 2;
// We ensure that the graph advances in steps that are multiples of the Web
// Audio block size
const uint32_t WEBAUDIO_BLOCK_SIZE_BITS = 7;
const uint32_t WEBAUDIO_BLOCK_SIZE = 1 << WEBAUDIO_BLOCK_SIZE_BITS;
/**
* An AudioChunk represents a multi-channel buffer of audio samples.
* It references an underlying ThreadSharedObject which manages the lifetime
* of the buffer. An AudioChunk maintains its own duration and channel data
* pointers so it can represent a subinterval of a buffer without copying.
* An AudioChunk can store its individual channels anywhere; it maintains
* separate pointers to each channel's buffer.
*/
struct AudioChunk {
typedef mozilla::AudioSampleFormat SampleFormat;
// Generic methods
void SliceTo(TrackTicks aStart, TrackTicks aEnd)
{
NS_ASSERTION(aStart >= 0 && aStart < aEnd && aEnd <= mDuration,
"Slice out of bounds");
if (mBuffer) {
MOZ_ASSERT(aStart < INT32_MAX, "Can't slice beyond 32-bit sample lengths");
for (uint32_t channel = 0; channel < mChannelData.Length(); ++channel) {
mChannelData[channel] = AddAudioSampleOffset(mChannelData[channel],
mBufferFormat, int32_t(aStart));
}
}
mDuration = aEnd - aStart;
}
TrackTicks GetDuration() const { return mDuration; }
bool CanCombineWithFollowing(const AudioChunk& aOther) const
{
if (aOther.mBuffer != mBuffer) {
return false;
}
if (mBuffer) {
NS_ASSERTION(aOther.mBufferFormat == mBufferFormat,
"Wrong metadata about buffer");
NS_ASSERTION(aOther.mChannelData.Length() == mChannelData.Length(),
"Mismatched channel count");
if (mDuration > INT32_MAX) {
return false;
}
for (uint32_t channel = 0; channel < mChannelData.Length(); ++channel) {
if (aOther.mChannelData[channel] != AddAudioSampleOffset(mChannelData[channel],
mBufferFormat, int32_t(mDuration))) {
return false;
}
}
}
return true;
}
bool IsNull() const { return mBuffer == nullptr; }
void SetNull(TrackTicks aDuration)
{
mBuffer = nullptr;
mChannelData.Clear();
mDuration = aDuration;
mVolume = 1.0f;
}
TrackTicks mDuration; // in frames within the buffer
nsRefPtr<ThreadSharedObject> mBuffer; // the buffer object whose lifetime is managed; null means data is all zeroes
nsTArray<const void*> mChannelData; // one pointer per channel; empty if and only if mBuffer is null
float mVolume; // volume multiplier to apply (1.0f if mBuffer is nonnull)
SampleFormat mBufferFormat; // format of frames in mBuffer (only meaningful if mBuffer is nonnull)
};
/**
* A list of audio samples consisting of a sequence of slices of SharedBuffers.
* The audio rate is determined by the track, not stored in this class.
*/
class AudioSegment : public MediaSegmentBase<AudioSegment, AudioChunk> {
public:
typedef mozilla::AudioSampleFormat SampleFormat;
AudioSegment() : MediaSegmentBase<AudioSegment, AudioChunk>(AUDIO) {}
void AppendFrames(already_AddRefed<ThreadSharedObject> aBuffer,
const nsTArray<const float*>& aChannelData,
int32_t aDuration)
{
AudioChunk* chunk = AppendChunk(aDuration);
chunk->mBuffer = aBuffer;
for (uint32_t channel = 0; channel < aChannelData.Length(); ++channel) {
chunk->mChannelData.AppendElement(aChannelData[channel]);
}
chunk->mVolume = 1.0f;
chunk->mBufferFormat = AUDIO_FORMAT_FLOAT32;
}
void AppendFrames(already_AddRefed<ThreadSharedObject> aBuffer,
const nsTArray<const int16_t*>& aChannelData,
int32_t aDuration)
{
AudioChunk* chunk = AppendChunk(aDuration);
chunk->mBuffer = aBuffer;
for (uint32_t channel = 0; channel < aChannelData.Length(); ++channel) {
chunk->mChannelData.AppendElement(aChannelData[channel]);
}
chunk->mVolume = 1.0f;
chunk->mBufferFormat = AUDIO_FORMAT_S16;
}
// Consumes aChunk, and returns a pointer to the persistent copy of aChunk
// in the segment.
AudioChunk* AppendAndConsumeChunk(AudioChunk* aChunk)
{
AudioChunk* chunk = AppendChunk(aChunk->mDuration);
chunk->mBuffer = aChunk->mBuffer.forget();
chunk->mChannelData.SwapElements(aChunk->mChannelData);
chunk->mVolume = aChunk->mVolume;
chunk->mBufferFormat = aChunk->mBufferFormat;
return chunk;
}
void ApplyVolume(float aVolume);
void WriteTo(AudioStream* aOutput);
static Type StaticType() { return AUDIO; }
};
}
#endif /* MOZILLA_AUDIOSEGMENT_H_ */