bool QProcessProto::isWritable() const
{
QProcess *item = qscriptvalue_cast<QProcess*>(thisObject());
if (item)
return item->isWritable();
return false;
}
/** Runs the specified command (should be ffmpeg), and lets
* writeFrame pipe data into it 1 frame at a time.
*
* @param[in] strCmd A string containing the command to execute and
* all of its arguments
* @param[out] progress A function that takes one float argument
* (the percentage of the ffmpeg operation complete) and
* may display the output to the user in any way it
* sees fit.
* @param[in] writeFrame A function that takes two arguments, a
* process (the ffmpeg process) and an integer
* (frames processed or -1, see full description).
* This function should write a single frame to the
* process. The function returns true value if it
* actually wrote a frame.
*
* This function operates generally as follows:
* 1. Spawn process with the command from strCmd
* 2. Check ffmpeg's output for a progress update.
* 3. Add frames with writeFrame until it returns false.
* 4. Repeat from step 2 until all frames have been written.
*
* The idea is that there are two forms of processing occuring
* simultaneously, generating frames to send to ffmpeg, and ffmpeg
* encoding those frames. Whether these this actually occur
* concurrently or one after another appears to depend on the environment.
*
* The writeFrame function deserves a bit of extra details. It does
* not only return false when there is an error in generating or
* writing a frame, it also does it when it wants to "return control"
* to the rest of the executeFFMpegPipe function for the purposes of
* reading updates from ffmpeg's output. This should be done every
* once in a while if possible, but with some formats (specifically gif),
* all frames must be loaded before any processing can continue, so
* there is no point returning false for it until all frames have
* been written. writeFrame is also responsible for closing the writeChannel
* of the process when it has finished writing all frames. This indicates
* to executeFFMpegPipe that it no longer needs to call writeFrame.
*
* @return Returns Status::OK if everything went well, and Status::FAIL
* and error is detected (usually a non-zero exit code for ffmpeg).
*/
Status MovieExporter::executeFFMpegPipe(QString strCmd, std::function<void(float)> progress, std::function<bool(QProcess&, int)> writeFrame)
{
qDebug() << strCmd;
QProcess ffmpeg;
ffmpeg.setReadChannel(QProcess::StandardOutput);
// FFmpeg writes to stderr only for some reason, so we just read both channels together
ffmpeg.setProcessChannelMode(QProcess::MergedChannels);
ffmpeg.start(strCmd);
if (ffmpeg.waitForStarted())
{
int framesGenerated = 0;
int lastFrameProcessed = 0;
const int frameStart = mDesc.startFrame;
const int frameEnd = mDesc.endFrame;
while(ffmpeg.state() == QProcess::Running)
{
if (mCanceled)
{
ffmpeg.terminate();
return Status::CANCELED;
}
// Check FFmpeg progress
int framesProcessed = -1;
if(ffmpeg.waitForReadyRead(10))
{
QString output(ffmpeg.readAll());
QStringList sList = output.split(QRegExp("[\r\n]"), QString::SkipEmptyParts);
for (const QString& s : sList)
{
qDebug() << "[ffmpeg]" << s;
}
if(output.startsWith("frame="))
{
lastFrameProcessed = framesProcessed = output.mid(6, output.indexOf(' ')).toInt();
}
}
if(!ffmpeg.isWritable())
{
continue;
}
while(writeFrame(ffmpeg, framesProcessed))
{
framesGenerated++;
const float percentGenerated = framesGenerated / static_cast<float>(frameEnd - frameStart);
const float percentConverted = lastFrameProcessed / static_cast<float>(frameEnd - frameStart);
progress((percentGenerated + percentConverted) / 2);
}
const float percentGenerated = framesGenerated / static_cast<float>(frameEnd - frameStart);
const float percentConverted = lastFrameProcessed / static_cast<float>(frameEnd - frameStart);
progress((percentGenerated + percentConverted) / 2);
}
QString output(ffmpeg.readAll());
QStringList sList = output.split(QRegExp("[\r\n]"), QString::SkipEmptyParts);
for (const QString& s : sList)
{
qDebug() << "[ffmpeg]" << s;
}
if(ffmpeg.exitStatus() != QProcess::NormalExit)
{
qDebug() << "ERROR: FFmpeg crashed";
return Status::FAIL;
}
}
else
{
qDebug() << "ERROR: Could not start FFmpeg.";
return Status::FAIL;
}
return Status::OK;
}
