[gstreamer-bugs] [Bug 516649] [v4l2src] tries to VIDIOC_S_PARM without checking capabilities

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-good | Ver: HEAD CVS

Tim-Philipp Müller changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #105313|none                        |rejected
               Flag|                            |
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|HEAD                        |0.10.8




------- Comment #4 from Tim-Philipp Müller  2008-03-25 12:33 UTC -------
> I believe this patch is not correct. The statement
>   if (v4l2src->v4l2object->vcap.capabilities & V4L2_CAP_TIMEPERFRAME)
> is in error, because vcap is a v4l2_captureparm structure, whereas the flag
> V4L2_CAP_TIMEPERFRAME is only present in a v4l2_capability structure.

I think you're right. This is is the list of flags used in the capabilities
field of a v4l2_capability structure according to the docs:
http://www.linuxtv.org/downloads/video4linux/API/V4L2_API/spec/r13105.htm#DEVICE-CAPABILITIES

> You may wish to look at the corresponding part of the proposed patch in bug
> #520092 to see how (I believe) this may be done correctly.

I've committed something based on your patch now:

  2008-03-25  Tim-Philipp Müller  <tim at centricular dot net>

        Based on patch by: William M. Brack <wbrack at mmm com hk>

        * sys/v4l2/v4l2src_calls.c: (fractions_are_equal),
          (gst_v4l2src_set_capture):
          Check whether the device supports setting the framerate before
          trying to set it and then posting a warning or error if it doesn't
          work (#516649, #520092). Also compare fractions more correctly.

I guess it's better to output data with a non-wanted framerate than to error
out, at least while we require a framerate to be specified in the caps. Some
refactoring might be in order here one day.


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