Gstreamer Basic Tutorial / API (3: Dynamic pipelines)

[Nicolas Dufresne]

Le mer. 15 mai 2019 22 h 40, R C <cjvijf at gmail.com> a écrit :

> Hello,
>
> I am trying to get a little more familiar with gstreamer, and thought I'd
> do some
>
> of the "basic" programming tutorial examples.
>
>
> I did play with the 3rd example:
>
>
> https://gstreamer.freedesktop.org/documentation/tutorials/basic/dynamic-pipelines.html?gi-language=c
>
>
> If I copy the example, and compile it, it works, no surprise there. But
> when I change it and do the "exercise", I get some weirdness.
>
>
> What I noticed is (well I probably missed something)...  but the function
> call:
>
> data.sink = gst_element_factory_make ("autoaudiosink", "sink");
> According to the docs, the 2nd parameter can be 'whatever' you want to name it.
> Since I wanted to do the video part too, I figure I should change the name to
> "audio-something", and changed the second function call to:
>   data.convert = gst_element_factory_make ("audioconvert", "convert");   (original)
>   data.sink = gst_element_factory_make ("autoaudiosink", "audiosink");   (changed name)
>
> of course in the even handler (pad_added_handler), the name needs to be changed in to:
> GstPad *sink_pad = gst_element_get_static_pad (data->convert, "audiosink");
>
> Browsing through the code, that should be it, BUT it seems "sink_pad" always is NULL
>  and the pipeline elements don't/can't be linked. (see errors below)
>
> since this is supposed to be a simple example,  what am I missing?
>
> thanks,
>
> Ron
>
>
> errors:
> # ./basic-tutorial-3
> Pipeline state changed from NULL to READY:
> Received new pad 'src_0' from 'source':
>
> (basic-tutorial-3:14679): GStreamer-CRITICAL **: 20:22:54.991: gst_pad_is_linked: assertion 'GST_IS_PAD (pad)' failed
> It has type 'video/x-raw' which is not raw audio. Ignoring.
>
> I'm not really able to see all steps that lead you to this, but I can give
you a trick to help. G_DEBUG=fatal_criticals will make it abort on the
assertion, run this in gdb, and analyse the context that lead to that pad
being null.

>

> (basic-tutorial-3:14679): GStreamer-CRITICAL **: 20:22:54.992: gst_object_unref: assertion 'object != NULL' failed
> Received new pad 'src_1' from 'source':
>
> (basic-tutorial-3:14679): GStreamer-CRITICAL **: 20:22:54.992: gst_pad_is_linked: assertion 'GST_IS_PAD (pad)' failed
>
> (basic-tutorial-3:14679): GStreamer-CRITICAL **: 20:22:54.992: gst_pad_link_full: assertion 'GST_IS_PAD (sinkpad)' failed
> Type is 'audio/x-raw' but link failed.
>
> (basic-tutorial-3:14679): GStreamer-CRITICAL **: 20:22:54.992: gst_object_unref: assertion 'object != NULL' failed
> Error received from element source: Internal data stream error.
> Debugging information: gstbasesrc.c(2950): gst_base_src_loop (): /GstPipeline:test-pipeline/GstURIDecodeBin:source/GstSoupHTTPSrc:source:
> streaming stopped, reason not-linked (-1)
>
>
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