The QAudioOutput 类提供将音频数据发送给音频输出设备的接口。 更多...
| 头： | #include <QAudioOutput> |
| Since: | Qt 4.6 |
| 继承： | QObject |
| QAudioOutput (const QAudioFormat & format = QAudioFormat(), QObject * parent = 0) | |
| QAudioOutput (const QAudioDeviceInfo & audioDevice , const QAudioFormat & format = QAudioFormat(), QObject * parent = 0) | |
| ~QAudioOutput () | |
| int | bufferSize () const |
| int | bytesFree () const |
| qint64 | elapsedUSecs () const |
| QAudio::Error | error () const |
| QAudioFormat | format () const |
| int | notifyInterval () const |
| int | periodSize () const |
| qint64 | processedUSecs () const |
| void | reset () |
| void | resume () |
| void | setBufferSize (int value ) |
| void | setNotifyInterval (int ms ) |
| void | start (QIODevice * device ) |
| QIODevice * | start () |
| QAudio::State | state () const |
| void | stop () |
| void | suspend () |
| void | notify () |
| void | stateChanged (QAudio::State state ) |
The QAudioOutput 类提供将音频数据发送给音频输出设备的接口。
可以构造音频输出采用系统的 默认音频输出设备 。它也是可能的，创建 QAudioOutput 采用特有 QAudioDeviceInfo 。当创建音频输出时，还应发送 QAudioFormat 用于回放 (见 QAudioFormat 类描述了解细节)。
要播放文件：
Starting to play an audio stream is simply a matter of calling start () 采用 QIODevice . QAudioOutput will then fetch the data it needs from the io device. So playing back an audio file is as simple as:
QFile inputFile; // class member.
QAudioOutput *audioOutput; // class member.
...
void startPlaying()
{
inputFile.setFileName("/tmp/test.raw");
inputFile.open(QIODevice::ReadOnly);
QAudioFormat format;
// Set up the format, eg.
format.setFrequency(8000);
format.setChannels(1);
format.setSampleSize(8);
format.setCodec("audio/pcm");
format.setByteOrder(QAudioFormat::LittleEndian);
format.setSampleType(QAudioFormat::UnSignedInt);
QAudioDeviceInfo info(QAudioDeviceInfo::defaultOutputDevice());
if (!info.isFormatSupported(format)) {
qWarning()<<"raw audio format not supported by backend, cannot play audio.";
return;
}
audioOutput = new QAudioOutput(format, this);
connect(audioOutput,SIGNAL(stateChanged(QAudio::State)),SLOT(finishedPlaying(QAudio::State)));
audioOutput->start(&inputFile);
}
The file will start playing assuming that the audio system and output device support it. If you run out of luck, check what's up with the error () 函数。
After the file has finished playing, we need to stop the device:
void finishedPlaying(QAudio::State state)
{
if (state == QAudio::IdleState) {
audioOutput->stop();
inputFile.close();
delete audioOutput;
}
}
At any given time, the
QAudioOutput
will be in one of four states: active, suspended, stopped, or idle. These states are described by the
QAudio::State
enum. State changes are reported through the
stateChanged
() signal. You can use this signal to, for instance, update the GUI of the application; the mundane example here being changing the state of a
play/pause
button. You request a state change directly with
suspend
(),
stop
(),
reset
(),
resume
()，和
start
().
While the stream is playing, you can set a notify interval in milliseconds with setNotifyInterval (). This interval specifies the time between two emissions of the notify () signal. This is relative to the position in the stream, i.e., if the QAudioOutput is in the SuspendedState or the IdleState, the notify () signal is not emitted. A typical use-case would be to update a slider that allows seeking in the stream. If you want the time since playback started regardless of which states the audio output has been in, elapsedUSecs () is the function for you.
If an error occurs, you can fetch the error type 采用 error () function. Please see the QAudio::Error enum for a description of the possible errors that are reported. When an error is encountered, the state changes to QAudio::StoppedState . You can check for errors by connecting to the stateChanged () signal:
void stateChanged(QAudio::State newState)
{
switch (newState) {
case QAudio::StoppedState:
if (audioOutput->error() != QAudio::NoError) {
// Perform error handling
} else {
// Normal stop
}
break;
另请参阅 QAudioInput and QAudioDeviceInfo .
Construct a new audio output and attach it to parent . The default audio output device is used with the output format 参数。
Construct a new audio output and attach it to parent . The device referenced by audioDevice is used with the output format 参数。
销毁此音频输出。
Returns the audio buffer size in bytes.
If called before start (), returns platform default value. If called before start () but setBufferSize () was called prior, returns value set by setBufferSize (). If called after start (), returns the actual buffer size being used. This may not be what was set previously by setBufferSize ().
另请参阅 setBufferSize ().
Returns the free space available in bytes in the audio buffer.
NOTE: returned value is only valid while in QAudio::ActiveState or QAudio::IdleState state, otherwise returns zero.
Returns the microseconds since start () was called, including time in Idle and Suspend states.
返回错误状态。
返回 QAudioFormat 被使用。
[signal]
void
QAudioOutput::
notify
()
This signal is emitted when x ms of audio data has been processed the interval set by setNotifyInterval (x).
Returns the notify interval in milliseconds.
另请参阅 setNotifyInterval ().
Returns the period size in bytes.
Note: This is the recommended write size in bytes.
Returns the amount of audio data processed by the class since start () was called in microseconds.
Note: The amount of audio data played can be determined by subtracting the microseconds of audio data still in the systems audio buffer.
qint64 bytesInBuffer = bufferSize() - bytesFree(); qint64 usInBuffer = (qint64)(1000000) * bytesInBuffer / ( channels() * sampleSize() / 8 ) / frequency(); qint64 usPlayed = processedUSecs() - usInBuffer;
Drops all audio data in the buffers, resets buffers to zero.
Resumes processing audio data after a suspend ().
集 error () 到 QAudio::NoError . Sets state () 到 QAudio::ActiveState if you previously called start( QIODevice *). Sets state () 到 QAudio::IdleState if you previously called start (). emits stateChanged () 信号。
Note: signal will always be emitted during execution of the resume() function.
Sets the audio buffer size to value in bytes.
Note: This function can be called anytime before start (), calls to this are ignored after start (). It should not be assumed that the buffer size set is the actual buffer size used, calling bufferSize () anytime after start () will return the actual buffer size being used.
另请参阅 bufferSize ().
Sets the interval for notify () signal to be emitted. This is based on the ms of audio data processed not on actual real-time. The minimum resolution of the timer is platform specific and values should be checked with notifyInterval () to confirm actual value being used.
另请参阅 notifyInterval ().
使用 device 作为 QIODevice to transfer data. Passing a QIODevice allows the data to be transferred without any extra code. All that is required is to open the QIODevice .
If able to successfully output audio data to the systems audio device the state () 被设为 QAudio::ActiveState , error () 被设为 QAudio::NoError 和 stateChanged () 信号发射。
If a problem occurs during this process the error () 被设为 QAudio::OpenError , state () 被设为 QAudio::StoppedState and stateChanged () 信号发射。
In either case, the stateChanged () signal may be emitted either synchronously during execution of the start() function or asynchronously after start() has returned to the caller.
另请参阅 QIODevice .
返回指针指向 QIODevice being used to handle the data transfer. This QIODevice can be used to write() audio data directly.
If able to access the systems audio device the state () 被设为 QAudio::IdleState , error () 被设为 QAudio::NoError 和 stateChanged () 信号发射。
If a problem occurs during this process the error () 被设为 QAudio::OpenError , state () 被设为 QAudio::StoppedState and stateChanged () 信号发射。
In either case, the stateChanged () signal may be emitted either synchronously during execution of the start () function or asynchronously after start () has returned to the caller.
另请参阅 QIODevice .
返回音频处理的状态。
[signal]
void
QAudioOutput::
stateChanged
(
QAudio::State
state
)
此信号被发射当设备 state has changed. This is the current state of the audio output.
Stops the audio output, detaching from the system resource.
集 error () 到 QAudio::NoError , state () 到 QAudio::StoppedState and emit stateChanged () 信号。
Stops processing audio data, preserving buffered audio data.
集 error () 到 QAudio::NoError , state () 到 QAudio::SuspendedState and emit stateChanged () 信号。