tor-browser

AudioPacketizer.h (6566B)

---

/* -*- 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 AudioPacketizer_h_
#define AudioPacketizer_h_

#include <AudioSampleFormat.h>
#include <mozilla/Assertions.h>
#include <mozilla/PodOperations.h>
#include <mozilla/UniquePtr.h>

// Enable this to warn when `Output` has been called but not enough data was
// buffered.
// #define LOG_PACKETIZER_UNDERRUN

namespace mozilla {
/**
* This class takes arbitrary input data, and returns packets of a specific
* size. In the process, it can convert audio samples from 16bit integers to
* float (or vice-versa).
*
* Input and output, as well as length units in the public interface are
* interleaved frames.
*
* Allocations of output buffer can be performed by this class.  Buffers can
* simply be delete-d.  This is because packets are intended to be sent off to
* non-gecko code using normal pointers/length pairs
*
* Alternatively, consumers can pass in a buffer in which the output is copied.
* The buffer needs to be large enough to store a packet worth of audio.
*
* The implementation uses a circular buffer using absolute virtual indices.
*/
template <typename InputType, typename OutputType>
class AudioPacketizer {
public:
 AudioPacketizer(uint32_t aPacketSize, uint32_t aChannels)
     : mPacketSize(aPacketSize),
       mChannels(aChannels),
       mReadIndex(0),
       mWriteIndex(0),
       // Start off with a single packet
       mStorage(new InputType[aPacketSize * aChannels]),
       mLength(aPacketSize * aChannels) {
   MOZ_ASSERT(aPacketSize > 0 && aChannels > 0,
              "The packet size and the number of channel should be strictly "
              "positive");
 }

 void Input(const InputType* aFrames, uint32_t aFrameCount) {
   uint32_t inputSamples = aFrameCount * mChannels;
   // Need to grow the storage. This should rarely happen, if at all, once the
   // array has the right size.
   if (inputSamples > EmptySlots()) {
     // Calls to Input and Output are roughtly interleaved
     // (Input,Output,Input,Output, etc.), or balanced
     // (Input,Input,Input,Output,Output,Output), so we update the buffer to
     // the exact right size in order to not waste space.
     uint32_t newLength = AvailableSamples() + inputSamples;
     uint32_t toCopy = AvailableSamples();
     UniquePtr<InputType[]> oldStorage = std::move(mStorage);
     mStorage = mozilla::MakeUnique<InputType[]>(newLength);
     // Copy the old data at the beginning of the new storage.
     if (WriteIndex() >= ReadIndex()) {
       PodCopy(mStorage.get(), oldStorage.get() + ReadIndex(),
               AvailableSamples());
     } else {
       uint32_t firstPartLength = mLength - ReadIndex();
       uint32_t secondPartLength = AvailableSamples() - firstPartLength;
       PodCopy(mStorage.get(), oldStorage.get() + ReadIndex(),
               firstPartLength);
       PodCopy(mStorage.get() + firstPartLength, oldStorage.get(),
               secondPartLength);
     }
     mWriteIndex = toCopy;
     mReadIndex = 0;
     mLength = newLength;
   }

   if (WriteIndex() + inputSamples <= mLength) {
     PodCopy(mStorage.get() + WriteIndex(), aFrames, aFrameCount * mChannels);
   } else {
     uint32_t firstPartLength = mLength - WriteIndex();
     uint32_t secondPartLength = inputSamples - firstPartLength;
     PodCopy(mStorage.get() + WriteIndex(), aFrames, firstPartLength);
     PodCopy(mStorage.get(), aFrames + firstPartLength, secondPartLength);
   }

   mWriteIndex += inputSamples;
 }

 OutputType* Output() {
   uint32_t samplesNeeded = mPacketSize * mChannels;
   OutputType* out = new OutputType[samplesNeeded];

   Output(out);

   return out;
 }

 // Return the number of actual frames dequeued -- this can be lower than the
 // packet size when underruning or draining.
 size_t Output(OutputType* aOutputBuffer) {
   uint32_t samplesNeeded = mPacketSize * mChannels;
   size_t rv = 0;

   // Under-run. Pad the end of the buffer with silence.
   if (AvailableSamples() < samplesNeeded) {
     rv = AvailableSamples() / mChannels;
#ifdef LOG_PACKETIZER_UNDERRUN
     char buf[256];
     snprintf(buf, 256,
              "AudioPacketizer %p underrun: available: %u, needed: %u\n", this,
              AvailableSamples(), samplesNeeded);
     NS_WARNING(buf);
#endif
     uint32_t zeros = samplesNeeded - AvailableSamples();
     PodZero(aOutputBuffer + AvailableSamples(), zeros);
     samplesNeeded -= zeros;
   } else {
     rv = mPacketSize;
   }
   if (ReadIndex() + samplesNeeded <= mLength) {
     ConvertAudioSamples<InputType, OutputType>(mStorage.get() + ReadIndex(),
                                                aOutputBuffer, samplesNeeded);
   } else {
     uint32_t firstPartLength = mLength - ReadIndex();
     uint32_t secondPartLength = samplesNeeded - firstPartLength;
     ConvertAudioSamples<InputType, OutputType>(
         mStorage.get() + ReadIndex(), aOutputBuffer, firstPartLength);
     ConvertAudioSamples<InputType, OutputType>(
         mStorage.get(), aOutputBuffer + firstPartLength, secondPartLength);
   }
   mReadIndex += samplesNeeded;
   return rv;
 }

 void Clear() {
   mReadIndex = 0;
   mWriteIndex = 0;
 }

 uint32_t PacketsAvailable() const {
   return AvailableSamples() / mChannels / mPacketSize;
 }

 uint32_t FramesAvailable() const { return AvailableSamples() / mChannels; }

 bool Empty() const { return mWriteIndex == mReadIndex; }

 bool Full() const { return mWriteIndex - mReadIndex == mLength; }

 // Size of one packet of audio, in frames
 const uint32_t mPacketSize;
 // Number of channels of the stream flowing through this packetizer
 const uint32_t mChannels;

private:
 uint32_t ReadIndex() const { return mReadIndex % mLength; }

 uint32_t WriteIndex() const { return mWriteIndex % mLength; }

 uint32_t AvailableSamples() const { return mWriteIndex - mReadIndex; }

 uint32_t EmptySlots() const { return mLength - AvailableSamples(); }

 // Two virtual index into the buffer: the read position and the write
 // position.
 uint64_t mReadIndex;
 uint64_t mWriteIndex;
 // Storage for the samples
 mozilla::UniquePtr<InputType[]> mStorage;
 // Length of the buffer, in samples
 uint32_t mLength;
};

}  // namespace mozilla

#endif  // AudioPacketizer_h_