Problem recording webcam with FFMPEG and QProcess

Guigiidre

Hi everybody, I need some help for a very strange problem:

I try to reccord a video with my webcam and FFMPEG, when I use the Command line everything is OK:

ffmpeg.exe -y -f dshow -i video="Logitech HD Webcam C270" out.avi

but when I try to do the same thing with QProcess, it does not work:

QString program="C:/FFmpeg/bin/ffmpeg.exe";

     mProcess->setReadChannel(QProcess::StandardOutput);
     mProcess->setProcessChannelMode(QProcess::MergedChannels);

   QStringList  list;
   list<<"-y"<<"-f"<<"dshow"<<"-i"<<"video=Logitech HD Webcam C270"<<"output.avi";
  

  mProcess->start(program,list);

I ve got the following error:

"Stream mapping:\r\n  Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg4 (native))\r\nPress [q] to stop, [?] for help\r\nvideo=Logitech HD Webcam C270: I/O error\r\n"

I use Qt 5.11.3 with mingw

Thank you in avance for your help!

mranger90

did you try embedding quotes around "Logitech HD Webcam C270" in the argument list ?

Christian Ehrlicher

Does it work on the command line without Qt?

Guigiidre

@Christian-Ehrlicher yes it works with the command line and furthermore this code used to work properly before...
So I suspect the virus of defender of Windows 10 to annoy me...

jsulm

@Guigiidre said in Problem recording webcam with FFMPEG and QProcess:

So I suspect the virus of defender of Windows 10 to annoy me

Disable it and try again

SGaist

Hi,

@Guigiidre said in Problem recording webcam with FFMPEG and QProcess:

video=Logitech HD Webcam C270

Try passing video=\"Logitech HD Webcam C270\” to QProcess.

Guigiidre

Yes I disabled the virus defender end it worked well....
But on another laptop with the last version of Windows I had another type of problem.
I have an error of the type : QProcess::FailedToStart.
I Checked that the exe existed so I suspect that the last version of Windows is incompatible with the QProcess class (Qt 5.11.3)

jsulm

@Guigiidre You should connect the error signals to a slot and check what happens. QProcess should work on latest Windows as well, there is probably something else on that machine.

Guigiidre

@jsulm I did :-) but I have no more information...
Anyway I will stop using the QProcess class to reccord video with my webcam, it seems too tricky, instead
I think I will use a library like LibVLC to do it...