Running bash script from Qt using QProcess or system() give difference result from terminal

[Wong]

Hi..

I am trying the capture the image from usb camera using QProcess to run bash file. My bash script content is

mplayer -quiet -tv device=/dev/video0 -frames 1 -vf-add screenshot tv://

When I run this bash script from the terminal, it works fine (see picture)

However, when I run this bash script from within qt using

QProcess process ;
process.startDetached("/bin/bash", QStringList() << "-c" << "/path_to_file/capture.bash");

there is something mixed up with the camera's buffer. The resulted picture looks like an superimposed version from previous position here (the camera is on a pan-tilt base.

Has anyone ever encountered this problem?

[JonB]

@Wong
There is no effective difference between running a bash script directly from e.g. a terminal versus running QProcess::startDetached("/bin/bash", QStringList() << "-c" << "/path_to_file/capture.bash"). So I don't know why you find it is behaving any differently.

[Jessevg]

There would be no effective difference here, this looks more like your camera doing something funky with it's framebuffers, I don't think Qt would be doing something so wrong it's messing up framebuffer data that's captured from inside a script you're running

[SGaist]

Hi,

Since your bash script is basically a one liner, can you check what happens if you call mplayer directly from it ?