播放使用了QIODevice（Qt4.6用VC ++）音频数据 [英] Play audio data using QIODevice (Qt4.6 with VC++)
问题描述
我正在使用VC ++与QtMultimedia库中的音频流播放音频。由于我不是太与Qt的图书馆经历，我开始通过阅读.wav文件，并将其写入缓冲区：
I'm working on playing audio from an audio stream using VC++ with the QtMultimedia library. Since I'm not too experienced with Qt's libraries I started by reading in a .wav file and writing it to a buffer:
ifstream wavFile;
char* file = "error_ex.wav";
wavFile.open( file, ios::binary );
在这之后，我用的ifstream的.read（）函数，所有的数据写入到缓冲区中。在缓冲区被写入后，它的被罚下到音频笔者，prepares它的Qt：
After that, I used ifstream's .read() function and write all the data into a buffer. After the buffer is written it's sent off to the audio writer that prepares it for Qt:
QByteArray fData;
for( int i = 0; i < (int)data.size(); ++i )
{
fData.push_back(data.at(i));
}
m_pBuffer->open(QIODevice::ReadWrite);
m_pBuffer->write( fData );
m_pBuffer->close();
（m_pBuffer的类型是ΣQ缓冲的）
(m_pBuffer is of type QBuffer)
一旦ΣQ缓冲准备好我尝试播放缓冲：
Once the QBuffer is ready I attempt to play the buffer:
QIODevice* ioDevice = m_pAudioOut->start();
ioDevice->write( m_pBuffer->buffer() );
（m_pAudioOut的类型是QAudioOutput的）
(m_pAudioOut is of type QAudioOutput)
这导致从扬声器小流行，然后停止播放。任何想法，为什么？
This results in a small pop from the speakers and then it stops playing. Any ideas why?
使用Qt库4.6.3在Windows XP SP2上运行的视觉工作室2008年。
Running Visual Studios 2008 on Windows XP SP2 using Qt library 4.6.3.
推荐答案
弗兰克指出，如果你的要求是简单地从一个文件播放音频数据，更高级别的API会做的作业，可以简化您的应用程序code。 声子将是一个选项;此外，该项目将QtMobility提供 QMediaPlayer API，用于高层次的用例。
As Frank pointed out, if your requirement is simply to play audio data from a file, a higher-level API would do the job, and would simplify your application code. Phonon would be one option; alternatively, the QtMobility project provides the QMediaPlayer API for high-level use cases.
由于这个问题是专门关于使用的QIODevice 然而，那你提到阅读从WAV文件只是你的初使的方法，我会假设你确实需要一个流API，即其中一个允许客户端来控制缓冲，而不是交给这个控件到更高层次的抽象，如声子。
Given that the question is specifically about using QIODevice however, and that you mentioned that reading from a WAV file was just your intitial approach, I'll assume that you actually need a streaming API, i.e. one which allows the client to control the buffering, rather than handing over this control to a higher-level abstraction such as Phonon.
QAudioOutput 的可以在两种不同模式下使用，这取决于<$的c超载$ C>开始（）正所谓：
QAudioOutput can be used in two different modes, depending on which overload of start() is called:
在此模式下，QAudioOutput将拉动从提供的QIODevice数据，而不从客户端进一步干预。这是一个很好的选择，如果正在使用的QIODevice是其中之一是由Qt的（如： QFile时提供 ， QAbstractSocket 等）。
In this mode, QAudioOutput will pull data from the supplied QIODevice without further intervention from the client. It is a good choice if the QIODevice being used is one which is provided by Qt (e.g. QFile, QAbstractSocket etc).
推模式： 的QIODevice * QAudioOutput ::开始（）
在这种模式下，客户端QAudioOutput必须通过调用推送模式，音频设备的QIODevice ::写（）。这将需要在一个循环做，是这样的：
In this mode, the QAudioOutput client must push mode to the audio device by calling QIODevice::write(). This will need to be done in a loop, something like:
qint64 dataRemaining = ... // assign correct value here
while (dataRemaining) {
qint64 bytesWritten = audioOutput->write(buffer, dataRemaining);
dataRemaining -= bytesWritten;
buffer += bytesWritten;
// Then wait for a short time
}
如何等待实现将取决于应用程序的情况下 - 如果声音是从一个专门的线程编写的，它可以简单的睡眠（）。另外，如果声音是从主线程写的，你可能会想在写一个 QTimer被触发。
How the wait is implemented will depend on the context of your application - if audio is being written from a dedicated thread, it could simply sleep(). Alternatively, if audio is being written from the main thread, you will probably want the write to be triggered by a QTimer.
既然你不提关于使用周围的写入（一个循环任何东西）在你的应用程序调用，它看起来像正在发生的事情是，你写数据的短段（其中扮演一个弹出），然后穿上未写了。
Since you don't mention anything about using a loop around the write() calls in your app, it looks like what is happening is that you write a short segment of data (which plays as a pop), then don't write any more.
您可以使用它使用Qt提供的例子/多媒体/ audiooutput应用这两种模式见code。
You can see code using both modes in the examples/multimedia/audiooutput app which is delivered with Qt.
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