Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
On Mon, 19 Jul 2010 19:46:00 +0100 Darren Salt li...@youmustbejoking.demon.co.uk wrote: I demand that Tony Houghton may or may not have written... I've noticed sync problems on those and they could well have been ones I recorded from one of the C4 channels. But I usually record them from satellite rather than Freeview. Well... if the patch fixes those problems... It looks like it does. I had a recording of an old (but colour) film from Film 4 where the sync was way out, but it's much improved with the patch. Can the patch (or similar fix) be included in the next Debian release of libxine1? I had a lot of trouble satisfying its build dependencies on my unstable system. ___ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
I demand that Tony Houghton may or may not have written... On Mon, 19 Jul 2010 19:46:00 +0100 Darren Salt li...@youmustbejoking.demon.co.uk wrote: I demand that Tony Houghton may or may not have written... I've noticed sync problems on those and they could well have been ones I recorded from one of the C4 channels. But I usually record them from satellite rather than Freeview. Well... if the patch fixes those problems... It looks like it does. I had a recording of an old (but colour) film from Film 4 where the sync was way out, but it's much improved with the patch. Looks like I guessed right when including the patch in 1.1.19, then. :-) Can the patch (or similar fix) be included in the next Debian release of libxine1? No, but it could be in libxine1-bin. ;-) I had a lot of trouble satisfying its build dependencies on my unstable system. No such trouble here, but then I always build from the repository or from packaged source... -- | Darren Salt| linux at youmustbejoking | nr. Ashington, | Toon | using Debian GNU/Linux | or ds,demon,co,uk| Northumberland | back! | Let's keep the pound sterling How sharper than a hound's tooth it is to have a thankless serpent. ___ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
I demand that Günter Merz may or may not have written... I've found a solution to my longstanding problem: Video and audio being out of sync on my vdr system using xine-lib as output display/control application. [snip] --- src/libmad/xine_mad_decoder.c.old 2010-07-17 20:00:54.0 +0200 +++ src/libmad/xine_mad_decoder.c 2010-07-17 20:02:10.0 +0200 [snip] I hope this is helpful to other people. Probably. (Would be nice if you – and others – would Cc xine-lib patches to xine-devel, or mention them in #xine.) Anyway, I've (sometimes) seen sync problems with Channel 4 channels on Freeview, though I rarely watch those channels; it's possible that both cause and fix are the same. I've committed the patch locally (for now). -- | Darren Salt| linux at youmustbejoking | nr. Ashington, | Toon | using Debian GNU/Linux | or ds,demon,co,uk| Northumberland | back! | + Travel less. Share transport more. PRODUCE LESS CARBON DIOXIDE. Microsoft. What Shall We Tell You That You Can Do Today? ___ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
On Mon, 19 Jul 2010 17:00:12 +0100 Darren Salt li...@youmustbejoking.demon.co.uk wrote: Anyway, I've (sometimes) seen sync problems with Channel 4 channels on Freeview, though I rarely watch those channels; it's possible that both cause and fix are the same. I've committed the patch locally (for now). Were they old black white films by any chance? I've noticed sync problems on those and they could well have been ones I recorded from one of the C4 channels. But I usually record them from satellite rather than Freeview. ___ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
I've found a solution to my longstanding problem: Video and audio being out of
sync on my vdr system using xine-lib as output display/control application.
Having excluded basically any other component, I started debugging xine-lib.
The first thing I've found was: When video and audio become out of sync,
metronome doesn't seem to get any audio pts anymore, they are always 0.
I checked the mpeg_pes demuxer but the audio pts were read from the stream
throughout.
The xine libmad adaptor seemed not to forward the pts to the metronome:
It buffers the MPEG audio packets until a threshold is reached (MAD_MIN_SIZE:
2889 bytes) and then has libmad decode the packets which is send to audio out.
The pts of the last audio packet is forwarded on to metronome which can then
sync video with audio.
For the channel4 channels MPEG audio packets have a size of 576 bytes which
means it takes five packets to fill the buffer enough for processing. In the
stream every fifth audio packet contains a pts.
The result of this is: If after a seek, the last audio packet is the one with
the pts, video and audio are in sync. If the pts is in any of the four previous
ones no pts will reach metronome and video and audio will never be synced before
a new seek and even then there's a one in five chance that video and audio are
not synced.
Other channels did not show this behaviour because e.g. BBC One has an audio
packet size of about 750 bytes and send a pts every fifth packet as well. This
means that not every pts from the stream gets through to metronome but some do.
This also means that syncing after a seek is probably not as quick as it could
be but it will sync.
My workaround to this problem is for the libmad xine adaptor (1.2 version) to
start decoding not only when a the buffer has reached a theshold but also when a
pts != 0 arrives. This does mean however that the buffer isn't always filled to
the theshold and decoding might not perform as well as it could (xine developers
are welcome to think of a better solution):
--- src/libmad/xine_mad_decoder.c.old 2010-07-17 20:00:54.0 +0200
+++ src/libmad/xine_mad_decoder.c 2010-07-17 20:02:10.0 +0200
@@ -190,7 +190,7 @@
mad_stream_buffer (this-stream, this-buffer,
this-bytes_in_buffer);
-if (this-bytes_in_buffer MAD_MIN_SIZE)
+if (this-bytes_in_buffer MAD_MIN_SIZE buf-pts == 0)
return;
if (!this-needs_more_data) {
I hope this is helpful to other people.
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Re: [vdr] A/V out of sync for BSkyB channels Channel4, More4, E4, Film4
Meanwhile, I've played back a vdr recording in xine (xine-ui) (the file itself, not through vdr) and can confirm the a/v sync problem is still there. I played back the same recording with mplayer and the a/v sync problem seems to be gone---maybe with the small note that mplayer takes a few moments to adjust. This pretty much rules out vdr and vdr-xine as the source of the problem as well. As far as I know, mplayer and ffmpeg use the same codebase (mostly). From the above, I deduce that xine-lib or my configuration thereof produces the a/v sync problem. Can anyone confirm or contradict my thesis? If it is in fact xine-lib that is the problem, does anyone know how to approach the problem? ___ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
