gecko/content/media/nsAudioStream.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
2012-05-21 04:12:37 -07:00
/* 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(nsAudioStream_h_)
#define nsAudioStream_h_
#include "nscore.h"
#include "nsISupportsImpl.h"
#include "nsIThread.h"
#include "nsAutoPtr.h"
// Access to a single instance of this class must be synchronized by
// callers, or made from a single thread. One exception is that access to
// GetPosition, GetPositionInFrames, SetVolume, and Get{Rate,Channels,Format}
// is thread-safe without external synchronization.
class nsAudioStream : public nsISupports
{
public:
enum SampleFormat
{
FORMAT_U8,
FORMAT_S16_LE,
FORMAT_FLOAT32
};
nsAudioStream()
: mRate(0),
mChannels(0),
mFormat(FORMAT_S16_LE)
{}
virtual ~nsAudioStream();
// Initialize Audio Library. Some Audio backends require initializing the
// library before using it.
static void InitLibrary();
// Shutdown Audio Library. Some Audio backends require shutting down the
// library after using it.
static void ShutdownLibrary();
// Thread that is shared between audio streams.
// This may return null in the child process
nsIThread *GetThread();
// AllocateStream will return either a local stream or a remoted stream
// depending on where you call it from. If you call this from a child process,
// you may receive an implementation which forwards to a compositing process.
static nsAudioStream* AllocateStream();
// Initialize the audio stream. aNumChannels is the number of audio
// channels (1 for mono, 2 for stereo, etc) and aRate is the sample rate
// (22050Hz, 44100Hz, etc).
// Unsafe to call with a monitor held due to synchronous event execution
// on the main thread, which may attempt to acquire any held monitor.
virtual nsresult Init(PRInt32 aNumChannels, PRInt32 aRate, SampleFormat aFormat) = 0;
// Closes the stream. All future use of the stream is an error.
// Unsafe to call with a monitor held due to synchronous event execution
// on the main thread, which may attempt to acquire any held monitor.
virtual void Shutdown() = 0;
// Write audio data to the audio hardware. aBuf is an array of frames in
// the format specified by mFormat of length aCount. If aFrames is larger
// than the result of Available(), the write will block until sufficient
// buffer space is available.
virtual nsresult Write(const void* aBuf, PRUint32 aFrames) = 0;
// Return the number of audio frames that can be written without blocking.
virtual PRUint32 Available() = 0;
// Set the current volume of the audio playback. This is a value from
// 0 (meaning muted) to 1 (meaning full volume). Thread-safe.
virtual void SetVolume(double aVolume) = 0;
// Block until buffered audio data has been consumed.
// Unsafe to call with a monitor held due to synchronous event execution
// on the main thread, which may attempt to acquire any held monitor.
virtual void Drain() = 0;
// Pause audio playback
virtual void Pause() = 0;
// Resume audio playback
virtual void Resume() = 0;
// Return the position in microseconds of the audio frame being played by
// the audio hardware. Thread-safe.
virtual PRInt64 GetPosition() = 0;
// Return the position, measured in audio frames played since the stream
// was opened, of the audio hardware. Thread-safe.
virtual PRInt64 GetPositionInFrames() = 0;
// Returns true when the audio stream is paused.
virtual bool IsPaused() = 0;
// Returns the minimum number of audio frames which must be written before
// you can be sure that something will be played.
// Unsafe to call with a monitor held due to synchronous event execution
// on the main thread, which may attempt to acquire any held monitor.
virtual PRInt32 GetMinWriteSize() = 0;
int GetRate() { return mRate; }
int GetChannels() { return mChannels; }
SampleFormat GetFormat() { return mFormat; }
protected:
nsCOMPtr<nsIThread> mAudioPlaybackThread;
int mRate;
int mChannels;
SampleFormat mFormat;
};
#endif