[gst-devel] Getting converted frame from playbin2 element

Marco Ballesio gibrovacco at gmail.com
Tue Jan 18 21:43:29 CET 2011


Hi,

looks like my time machine for jumping 11 days in the future
eventually works.. (lame excuse for my late reply)

Maybe you've already fixed your issue, but I still have a few ideas.

On Mon, Jan 10, 2011 at 4:15 PM, vaisaari <vaisaari at gmail.com> wrote:
>
>> imo this should not happen, as the signal handler (delegated to
>> playsink) internally calls gst_play_sink_get_last_frame, which locks
>> playsink. Can you post to pastebin the output you get after setting
>> GST_DEBUG=playsink:5 ?
>
> You can find the output from  http://pastebin.com/raw.php?i=HgD1S8Uz here  .
> The output looks the same whether or not the conversion is successful.

yep, it looks good.

>
>> Which video decoder are you using?
>
> I have tried it with both uncompressed and MPEG4 encoded videos.
>
>> Besides, if you're trying to render a video clip in Qt, you may
>> consider using QtGStreamer..
>
> It looks very promising. At some point, I most certainly will.

here:

http://doc.qt.nokia.com/qt-maemo-4.7/qimage.html#QImage-4

is stated the validity of the data into memory must last at least as
long as the QImage itself and in the list you've reported it appears
you're not handling buffer references at all. At best, you're leaking
memory like there's no tomorrow, at worst (depending on the pov) the
buffer "buffer" gets unreffed somewhere by chances and then you might
observed teared images (depending on the color space) or even
segfaults. Another good reason for using QtGstreamer ;)

Even if it worked, I would anyway not use such an approach to convert
all the frames in a clip (check what does the gst_video_convert_frame
function do to be convinced). It's imo better to use a color space
conversion element (e.g. ffmpegcolorspace) at the end of the pipeline
or after a tee and an appsink element.

Regards,
Marco

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