[FFmpeg-user] Python / Qprocess misfires commands.

Bouke bouke at editb.nl
Tue May 18 13:05:40 EEST 2021

> On 18 May 2021, at 09:33, Moritz Barsnick <barsnick at gmx.net> wrote:
> On Mon, May 17, 2021 at 09:19:46 +0200, Bouke wrote:
>>> You will have to show/look at the console output of both commands.
>>> (It's there for a reason, and most likely says what the issue is.)
>> I know, but there was ’nothing’ on stdErr / stdOut.
> Then you're capturing your output incorrectly.

Nah, this was an apology for an earlier message where I ment ’nothing except the banner'

>> It turns out that FFmpeg crashes, nothing wrong with the command line.
>> QProcess sees an error, and either QProcess terminates FFmpeg (I don’t think so) or FFmpeg crashes by itself.
> If QProcess terminates it unconditionally, there's nothing we can do(?).

I understand, but now it’s the blame game, what happens where / when / why?

> If ffmpeg crashes, that's bad. You would have to convince your system
> to create a core dump, and would have to look at a backtrace. (Or run
> ffmpeg within gdb.)

Eeh, I’m a simple scripter, not a coder, no clue how to do that...

>> in Python:
>> cmd = "bash"
>> args = ["-c", "/Applications/ffmpeg -loglevel trace -report -f avfoundation -i :0 /Volumes/Data/test.mov"]
> Do you need to run it in bash? Can you not set cmd to "ffmpeg" and
> properly pass the arguments?

Normally I do that, especially as that saves tons of headaches on escaping stuff.
But this was a suggestion from the QT forum, hoping it would provide a bit more insight.
https://forum.qt.io/topic/126674/escaping-colon-in-command-line-argument/8 <https://forum.qt.io/topic/126674/escaping-colon-in-command-line-argument/8>

Trust me, it makes no difference if I use separate args or run it as bash.


> Regards,
> Moritz
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