complete-request callback not called in Qt5 program

[Barnabás Pőcze]

Hi

2025. 05. 15. 12:12 keltezéssel, Stefan Geißler írta:
> Hello
> 
> I use libcamera 0.5 in C++ in a Qt5 program on an NXP 8.
> 
> The callback for the request completed is not called, while the program runs.

How do you confirm that? The steps I would take:

   1. attach a debugger and place a breakpoint to confirm that it is not called
   2. use `strace` to check if there are any `ioctl(VIDIOC_DQBUF, ...)`
   3. attach a debugger and inspect the stack traces of all threads
      to see if anything in libcamera or your code is maybe waiting for
      a futex or similar


> 
> It is called after I ended the program.

Can you clarify what you mean by this? When a camera is stopped, all outstanding
requests should be returned to the application as "cancelled". Maybe that is
what you're seeing.


> 
> The libcamera source code is based on the C++ code in the tutorial.
> 
> The C++ tutorial code as command line program works well.

In that case you should check if the camera is properly configured and started,
and if enough requests are actually queued. You could run both with `LIBCAMERA_LOG_LEVELS=DEBUG`
and potentially compare them.


Regards,
Barnabás Pőcze

> 
> What am I missing?
> 
> Thank you
> 
> Stefan
>