rtspsrc - pad-added signal - correct handling

[Nicolas Dufresne]

Le lun. 4 nov. 2019 15 h 10, Bill Klein <bill at orbit.org> a écrit :

> I am using a pipeline with an rtsp src in C code. Everything has been
> working mostly wonderfully, but recent issues have led me to believe that I
> am doing something wrong in certain situations. Specifically, I am
> wondering if I am handling the *pad-added* signal correctly.
>
> My pad-added handler is something simple like (simplified for the sake of
> readability):
>
> void on_pad_added(GstElement* element, GstPad* pad, void *data) {
>     GstPad* sinkpad = gst_element_get_static_pad(depay_el, "sink");
>     if(!sinkpad) ... // handle error
>
>     auto r = gst_pad_link(pad, sinkpad);
>
>     auto padnm = gst_pad_get_name(pad);
>     log("on_pad_added - "+padnm+" result:"+getPadLinkRespStr(rs));
>     // free paddnm...
>
>     gst_object_unref(sinkpad);
> }
>
>
> A few questions about this:
>
>    - Is the above correct/sufficient?
>
>    - Sometimes gst_pad_link returns GST_PAD_LINK_NOFORMAT. Is that
>    expected/normal? Do I need to perform additional handling in that case (ex
>    unrefing the element)?
>
>
Means the link failed. There was not matching formats on these pads. You
are doing something incorrect. Trace the caps on both ends to debug.


>    -
>    - Sometimes gst_pad_link returns GST_PAD_LINK_WAS_LINKED. Is that
>    expected/normal? Do I need to perform additional handling in that case (ex
>    unrefing the element)?
>
> You are trying to link twice a pad, this is a programming error. If you
need to relink, the make sure to unlink first.

>
>    -
>    - For some networks/rtsp cameras, I see only a few pad-added signals
>    called. In others, I see 100s (recv_rtp_src_***). Is that normal?
>
> Most cameras will expose two streams, audio and video. This seems rather
strange to see so many pads, would need more data.

Thank you!
>
> - Bill
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