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rtpjitterbuffer: stops processing when mode=buffer and drop-on-latency=1

Submitted by tia..@..il.com

Link to original bug (#646167)

Description

I was doing some tests with gstrtpjitterbuffer, basically generating audio with audiotestsrc and sending it using rtp (ptime must be 20ms on my tests).

The pipeline used to generate audio is:

gst-launch -m audiotestsrc is_live=true ! alawenc ! audio/x-alaw,rate=8000,channels=1 ! rtppcmapay min-ptime=20000000 max-ptime=20000000 ! udpsink host=127.0.0.1 port=5000

And on the receive side i have an application that does some measurements using pad probing on the gstrtpjitterbuffer element. Everything was ok until i started to set the gstrtpjitterbuffer "mode" property to "buffer". I got a little audio and them silence. First thing i thought was "my test must be broken". But when i started to debug to find out what i was doing wrong i found that what was making my test getting locked was:

g_object_set(G_OBJECT (jitter_buffer), "drop-on-latency", TRUE, NULL);

so i tried to reproduce the problem using gst-launch and it really stops processing, (the "buffering" message gets on 71% and stops, no audio is heard). If i don't set drop-on-latency=1, this don't happens, or if the mode is not buffer it works with drop-on-latency=1.

Basically:

works: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=none drop-on-latency=1 ! decodebin ! autoaudiosink

works: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=none drop-on-latency=0 ! decodebin ! autoaudiosink

works: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=slave drop-on-latency=1 ! decodebin ! autoaudiosink

works: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=slave drop-on-latency=0 ! decodebin ! autoaudiosink

works: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=buffer drop-on-latency=0 ! decodebin ! autoaudiosink

stop processing on 71%: gst-launch udpsrc port=5000 caps=application/x-rtp,clock-rate=8000 ! gstrtpptdemux ! gstrtpjitterbuffer mode=buffer drop-on-latency=1 ! decodebin ! autoaudiosink

i didn't find anything saying that the drop-on-latency property must not be set to true when the buffering mode is "buffer", so i thought this must be a bug (it is pretty simple to reproduce and the pipelines are quite simple too).

The problem happened on Ubuntu 10.10/Gstreamer 0.10.30.