Bug#863663: libgstreamer1.0-0: plays MJPEG AVI files (and possibly other formats) at degraded quality

[Sebastian Dröge]

On Thu, 2017-06-01 at 23:47 +0200, Francesco Poli wrote:
> On Thu, 01 Jun 2017 09:21:16 +0300 Sebastian Dröge wrote:
> 
> > On Wed, 2017-05-31 at 22:14 +0200, Francesco Poli wrote:
> 
> [...]
> > > How can I force GStreamer to use the ffmpeg based decoder with
> > > gst-launch-1.0?
> > > And from within an application that uses the GStreamer library?
> > 
> > See what I wrote in the upstream bug report. You can explicitly use
> > avdec_mjpeg in a custom pipeline.
> 
> It seems to me that there are two identical command lines in the
> upstream bug report. Or did I misunderstand something?
> 
> I tried with
> 
>   $ gst-launch-1.0 filesrc location=wave_anim.avi \! avidemux \!
> avdec_mjpeg \! autovideosink
>   $ gst-launch-1.0 filesrc location=wave_anim.avi \! avdec_mjpeg \!
> autovideosink
> 
> to no avail.
> Both pipelines abort with errors (although they spit different error
> messages).

The first, but with adding jpegparse between avidemux and avdec_mjpeg
should work. And potentially adding a videoconvert before
autovideosink.

> I apologize, but I am totally clueless about the meaning of GStreamer
> pipelines... Please bear with me...   :-(
> 
> > 
> > For using it automatically in decodebin/playbin, you would have to
> > adjust the ranks of jpegparse and avdec_mjpeg. Either by changing
> > their
> > code, or from your application with gst_plugin_feature_set_rank().
> 
> As documented [here]?
> 
> [here]: <http://www.manpagez.com/html/gstreamer-1.0/gstreamer-1.0-1.4
> .5/GstPluginFeature.php#gst-plugin-feature-set-rank>
> 
> Which is the feature that corresponds to avdec_mjpeg?
> Which is the one corresponding to jpegdec?

You could get them from the registry by exactly those names with
gst_registry_find_feature(). The type is GST_TYPE_ELEMENT_FACTORY.
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