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> |
| qmake: | QT += multimedia |
| 繼承： | QObject |
| QAudioOutput (const QAudioFormat & format = QAudioFormat(), QObject * parent = nullptr) | |
| QAudioOutput (const QAudioDeviceInfo & audioDevice , const QAudioFormat & format = QAudioFormat(), QObject * parent = nullptr) | |
| virtual | ~QAudioOutput () |
| int | bufferSize () const |
| int | bytesFree () const |
| QString | category () 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 | setCategory (const QString & category ) |
| void | setNotifyInterval (int ms ) |
| void | setVolume (qreal volume ) |
| void | start (QIODevice * device ) |
| QIODevice * | start () |
| QAudio::State | state () const |
| void | stop () |
| void | suspend () |
| qreal | volume () const |
| void | notify () |
| void | stateChanged (QAudio::State state ) |
| const QMetaObject | staticMetaObject |
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 sourceFile; // class member. QAudioOutput* audio; // class member. { sourceFile.setFileName("/tmp/test.raw"); sourceFile.open(QIODevice::ReadOnly); QAudioFormat format; // Set up the format, eg. format.setSampleRate(8000); format.setChannelCount(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; } audio = new QAudioOutput(format, this); connect(audio, SIGNAL(stateChanged(QAudio::State)), this, SLOT(handleStateChanged(QAudio::State))); audio->start(&sourceFile); }
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 AudioOutputExample::handleStateChanged(QAudio::State newState) { switch (newState) { case QAudio::IdleState: // Finished playing (no more data) audio->stop(); sourceFile.close(); delete audio; break; case QAudio::StoppedState: // Stopped for other reasons if (audio->error() != QAudio::NoError) { // Error handling } break; default: // ... other cases as appropriate break; } }
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 AudioOutputExample::handleStateChanged(QAudio::State newState) { switch (newState) { case QAudio::IdleState: // Finished playing (no more data) audio->stop(); sourceFile.close(); delete audio; break; case QAudio::StoppedState: // Stopped for other reasons if (audio->error() != QAudio::NoError) { // Error handling } break; default: // ... other cases as appropriate 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。
[虛擬]
QAudioOutput::
~QAudioOutput
()
銷毀此音頻輸齣。
This will release any system resources used and free any buffers.
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 number of free bytes available in the audio buffer.
注意： The returned value is only valid while in QAudio::ActiveState or QAudio::IdleState state, otherwise returns zero.
Returns the audio category of this audio stream.
Some platforms can group audio streams into categories and manage their volumes independently, or display them in a system mixer control. You can set this property to allow the platform to distinguish the purpose of your streams.
另請參閱 setCategory ().
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 a certain interval of milliseconds of audio data has been processed. The interval is set by setNotifyInterval ().
返迴通知間隔 (以毫秒為單位)。
另請參閱 setNotifyInterval ().
Returns the period size in bytes. This is the amount of data required each period to prevent buffer underrun, and to ensure uninterrupted playback.
注意： It is recommended to provide at least enough data for a full period with each write operation.
Returns the amount of audio data processed since start () was called (in microseconds).
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。
Sets the audio buffer size to value in bytes.
注意： 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 - call bufferSize () anytime after start () to return the actual buffer size being used.
另請參閱 bufferSize ().
Sets the audio category of this audio stream to category .
Some platforms can group audio streams into categories and manage their volumes independently, or display them in a system mixer control. You can set this property to allow the platform to distinguish the purpose of your streams.
Not all platforms support audio stream categorization. In this case, the function call will be ignored.
Changing an audio output stream's category while it is opened will not take effect until it is reopened.
另請參閱 category ().
Sets the interval for notify () signal to be emitted. This is based on the ms of audio data processed, not on wall clock time. The minimum resolution of the timer is platform specific and values should be checked with notifyInterval () to confirm the actual value being used.
另請參閱 notifyInterval ().
把輸齣音量設為 volume .
按綫性比例縮放的音量是從
0.0
(無聲) 到
1.0
(全音量)。將鉗製超齣此範圍的值。
默認音量為
1.0
.
Note: Adjustments to the volume will change the volume of this audio stream, not the global volume.
通常，UI 音量控件應按非綫性比例縮放。例如，使用對數比例縮放將産生感知響度的綫性變化，這通常是用戶期望的音量控製。見 QAudio::convertVolume () 瞭解更多細節。
另請參閱 volume ().
Starts transferring audio data from the device to the system's audio output. The device 必須已打開以 ReadOnly or ReadWrite 模式。
若 QAudioOutput is able to successfully output audio data, state () 返迴 QAudio::ActiveState , error () 返迴 QAudio::NoError 和 stateChanged () 信號發射。
若在此過程中齣現問題， error () 返迴 QAudio::OpenError , state () 返迴 QAudio::StoppedState 和 stateChanged () 信號發射。
另請參閱 QIODevice .
返迴的指針指嚮內部 QIODevice being used to transfer data to the system's audio output. The device will already be open and write() can write data directly to it.
注意： 指針將變為無效，在流被停止或啓動另一個流之後。
若 QAudioOutput 能夠訪問係統音頻設備， state () 返迴 QAudio::IdleState , error () 返迴 QAudio::NoError 和 stateChanged () 信號發射。
若在此過程中齣現問題， error () 返迴 QAudio::OpenError , state () 返迴 QAudio::StoppedState 和 stateChanged () 信號發射。
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 並發射 stateChanged () 信號。
Returns the volume between 0.0 and 1.0 inclusive.
另請參閱 setVolume ().