[gst-devel] playback hangs with wallclock change

[Babineau, Denis]

Hi,

 

I'm thinking this might be a bug report but I thought I'd run it by the
mailing list first. I'm having an issue where video stutters/freezes
completely when the system clock is changed. I can cause this to happen
by simply playing  a video with playbin (in this case a theora stream)
and moving the clock ahead and back. For example, if I move back the
clock 1 minute, the video will hang for 1 minute. I have a callstack
that looks something like so:

 

#0  0xffffe410 in __kernel_vsyscall ()

#1  0xb794ce50 in ppoll () from /lib/libc.so.6

#2  0xb7b50db3 in gst_poll_wait (set=0x8468af0, timeout=63569646) at
gstpoll.c:1131

#3  0xb7b5e509 in gst_system_clock_id_wait_jitter_unlocked
(clock=0x8647848, entry=0x863cbb8, jitter=0xb1fa2be0, restart=1)

    at gstsystemclock.c:569

#4  0xb7b5ec73 in gst_system_clock_id_wait_jitter (clock=0x8647848,
entry=0x863cbb8, jitter=0xb1fa2be0) at gstsystemclock.c:658

#5  0xb7b231ea in gst_clock_id_wait (id=0x863cbb8, jitter=0xb1fa2be0) at
gstclock.c:381

#6  0xb612806f in gst_base_sink_wait_clock (sink=0x813a020,
time=4733333333, jitter=0xb1fa2be0) at gstbasesink.c:1689

#7  0xb612ab07 in gst_base_sink_render_object (basesink=0x813a020,
pad=0x8138850, obj=0x85abc10) at gstbasesink.c:1978

#8  0xb612c6b5 in gst_base_sink_queue_object_unlocked
(basesink=0x813a020, pad=0x8138850, obj=0x85abc10, prerollable=1)

    at gstbasesink.c:2558

#9  0xb61314dd in gst_base_sink_chain_unlocked (basesink=0x813a020,
pad=0x8138850, buf=0x85abc10) at gstbasesink.c:2916

...

 

The timeout (nanoseconds) in frame 2 appears to be reasonable given the
framerate, however it seems to be looping somewhere on those calls. I
have yet to delve deep enough into the code to completely understand the
clock synchronization but is there something that would easily allow me
to change the clock to perhaps rely on the CLOCK_MONOTONIC time instead
of CLOCK_REALTIME? (which appears to be the case)

 

Thanks

Denis

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