Trouble playing HTTP-URIs gapless in "playbin"

[Henner Zeller]

Hi,
I am maintainer of gmrender-resurrect [1], a UPnP renderer (forked from the
dormant 'gmrender' project). It is using gstreamer as backend.

Using the gstreamer "playbin" feature to set the next URI in an
"about-to-finish" callback, this UPnP renderer successfully implements
gapless playback, alas, not without trouble.

It turns out, that playing gapless with inputs from HTTP-URLs is leaking
threads, up to the point that things stop working. This is with
gstreamer-0.10. With gstreamer-1.0 setting HTTP URLs in the
"about-to-finish" callback does not seem to work at all.

This _does_ work with local file-URIs, so I believe this has to do with
different handling of network resources vs. local resources, i.e.
buffering, probably a separate thread handling the network input (and it
would explain why this hasn't been noticed before, because the usual
use-case is to read from files).

To reproduce, I created simplified test-code including Makefile and
test-sound in this public git repository that illustrates the behavior:

  https://github.com/hzeller/gstreamer-gapless-test

All it does is to re-set the original URI back once the "about-to-finish"
callback is called ... and exhibiting the described behavior:
  - gstreamer-0.1: runs out of threads on gapless playing URIs
  - gstreamer-1.0: does not handle well having the URI set in
about-to-finish callback.
   - both work with file URIs

Instructions to reproduce are under
  https://github.com/hzeller/gstreamer-gapless-test/blob/master/README.md

Maybe, this is a usage error, but I suspect it to be a bug. If you can
confirm that this _should_ work, then I am happy to file a bug, and
probably dig into the code to help working on a fix.

Thanks,
  Henner.

[1] https://github.com/hzeller/gmrender-resurrect
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