[vdr] xine plugin sync problems on analog channels

[Reinhard Nissl]

Hi,

Cristiano wrote:

> I am having some problem with vdr xine and analogtv plugin.
> 
> I have a client-server vdr installation based on vdr 1.3.34, xine 0.7.6 
> plugin, when I select a DVB channel I have no problems but if I select 
> an analog channel (stream generated by analogtv plugin 0.9.37 with ivtv 
> 0.4.0 and PVR 150 card) I had some sync problem: here is the xine log:
> 
> audio jump, diff=-51840
> audio_out: inserting 27627 0-frames to fill a gap of 51815 pts
> video jump
> bad_frame
> video jump
> video jump
> bad_frame
> video_out: throwing away image with pts 653020 because it's too old 
> (diff : 6489
> 9).
> 200 frames delivered, 14 frames skipped, 1 frames discarded
> video_out: throwing away image with pts 2753839 because it's too old 
> (diff : 418
> 6).
> bad_frame
> bad_frame
> video jump
> bad_frame
> bad_frame
> audio jump, diff=-51850
> audio_out: inserting 27655 0-frames to fill a gap of 51866 pts
> video jump
> bad_frame
> video jump
> bad_frame
> bad_frame
> 200 frames delivered, 7 frames skipped, 1 frames discarded
> video_out: throwing away image with pts 5052089 because it's too old 
> (diff : 4544).
> 200 frames delivered, 0 frames skipped, 1 frames discarded
> bad_frame
> audio jump, diff=-45370
> audio_out: inserting 24197 0-frames to fill a gap of 45382 pts
> video jump
> video jump
> video jump
> bad_frame
> video_out: throwing away image with pts 6157260 because it's too old 
> (diff : 54139).
> 
> Searching on the vdr mailing list I found a thread ("problem 
> vdr-xine-0.7.3 plugin") that seems to be related to this issue.
> I tried to "play" with WRAP_THRESHOLD values without good results
> 
> Did you have any suggestion?

Have a look into xineDevice.c, cXineDevice::PlayCommon3() and comment 
out the first "if (0)" (i. e. => "// if (0)"). This enables logging of 
PTS values on console and you can check the offset between audio and 
video PTS as well as the offset to xine's metronom.

The offset to xine must allways be positive and should be around 60000 
pts (= 2/3 seconds). If it gets too small or even negative, then xine 
will get buffer underruns which may cause the above issue.

Another parameter to play with is vdr-xine's prebuffer setting. If you 
enlarge the setting then the above offset to xine should enlarge, too. 
But there are some drawbacks: when VDR cannot dispose its data to the 
device, it clears the device (after consecutive poll timeouts) which 
discards the buffers and causes vdr-xine to setup the prebuffer again 
and again.

Especially the analogtv plugin uses "little" buffers for the encoder and 
therefore it is likely that vdr-xine's prebuffering overflows the 
encoder buffers which are then in turn cleared. The result is that there 
is almost no buffer although vdr-xine thinks to have a reasonable sized 
one (it's on my todolist to change prebuffering to consider xine's 
metronom).

For any reason (I still haven't discovered why) there is a difference in 
the achieveable buffer size when xine is already connected to vdr-xine 
and you switch to an analogtv channel respectively when xine connects to 
vdr-xine after VDR was tuned to the analogtv channel. Most often the 
latter works without the above mentioned issue.

Bye.
-- 
Dipl.-Inform. (FH) Reinhard Nissl
mailto:rnissl at gmx.de