The QAudioOutput 類提供將音頻數據發送給音頻輸齣設備的接口。 更多...
| 頭： | #include <QAudioOutput> |
| Since: | Qt 4.6 |
| 繼承： | 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 類提供將音頻數據發送給音頻輸齣設備的接口。
可以構造音頻輸齣采用係統的 默認音頻輸齣設備 。也是可能的，創建 QAudioOutput 采用特有 QAudioDeviceInfo 。當創建音頻輸齣時，還應發送 QAudioFormat 用於迴放 (見 QAudioFormat 類描述瞭解細節)。
要播放文件：
開始播放音頻流的問題是隻需調用 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);
}
文件將開始播放，假定音頻係統和輸齣設備支持它。若運氣不好，校驗怎麼瞭是采用 error () 函數。
文件播放完成後，需要停止設備：
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;
另請參閱 QAudioInput and QAudioDeviceInfo .
Construct a new audio output and attach it to parent . The default audio output device is used with the output format 參數。
Construct a new audio output and attach it to parent . The device referenced by audioDevice is used with the output format 參數。
銷毀此音頻輸齣。
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 ().
另請參閱 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.
返迴錯誤狀態。
返迴 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).
返迴通知間隔 (以毫秒為單位)。
另請參閱 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.
再繼續處理音頻數據後於 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 () 信號。
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.
另請參閱 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.
另請參閱 notifyInterval ().
使用 device 作為 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 () 被設為 QAudio::ActiveState , error () 被設為 QAudio::NoError 和 stateChanged () 信號發射。
If a problem occurs during this process the error () 被設為 QAudio::OpenError , state () 被設為 QAudio::StoppedState and stateChanged () 信號發射。
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.
另請參閱 QIODevice .
返迴指針指嚮 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 () 被設為 QAudio::IdleState , error () 被設為 QAudio::NoError 和 stateChanged () 信號發射。
If a problem occurs during this process the error () 被設為 QAudio::OpenError , state () 被設為 QAudio::StoppedState and stateChanged () 信號發射。
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.
另請參閱 QIODevice .
返迴音頻處理的狀態。
[signal]
void
QAudioOutput::
stateChanged
(
QAudio::State
state
)
此信號被發射當設備 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 () 信號。
Stops processing audio data, preserving buffered audio data.
集 error () 到 QAudio::NoError , state () 到 QAudio::SuspendedState and emit stateChanged () 信號。