[mythtv-users] Re: DVD recording sync issues with PVR 350
Cory Papenfuss
papenfuss at juneau.me.vt.edu
Fri May 6 13:35:40 UTC 2005
> After having used Project X for a long time now, and reading of these
> problems, I had a hunch it was the deumxing of the streams initially
> that may be causing the sync issues. After all, remuxing cannot add
> back what is not present in the demuxed streams, and so if the sync is
> not fixed at this stage, I can't see the remuxing magically sorting it
> out.
>
I had pretty much figured out that it was the demux/remux stage in
almost all of the "MythTV to DVD" scripties and HOWTOs out there that was
breaking the sync. After I looked into it, I discovered the that the
PTS/DTS info is that the ProgramStream level... once it's demuxed into ES
or PES's, you've screwed the pooch....
... UNLESS it's fixed before it's demuxed. After playing with ProjectX a
bit more, I see that at the end of his little parsing, he spits this out:
--> MPEG Audio (0xC0)
Audio PTS: first packet 00:00:00.333, last packet 02:08:19.185
Video PTS: start 1.GOP 00:00:00.400, end last GOP 02:08:21.192
-> adjusting audio at video-timeline
-> src_audio: MPEG-1, Layer2, 48000Hz, stereo, 192kbps, noCRC @ 00:00:00.000
!> 81 frame(s) (1944ms) added @ 02:07:16.992p
audio frames: wri/pre/skip/ins/add 318289/0/0/0/81 @ 02:07:18.936 done...
---> new File: /space/HOME_VIDEOS/Tape5.mpa
summary of created media files:
.Video (m2v): 228939 Frames 02:07:18.930
'/space/HOME_VIDEOS/Tape5.m2v'
Audio 0 (mp2): 318289 Frames 02:07:18.936 0/0/0/81
'/space/HOME_VIDEOS/Tape5.mpa'
=> 4372557132 bytes written...
That looks like he added 81 frames of audio (as padding?) to keep
demuxed sync. Also, he threw out a bunch of bad B-frames, etc in the .m2v
file.
> On my 2.4G system, demuxing takes only a few minutes - if its >30
> minutes there could either be significant errors, non standard
> settings in ProjectX, or lots of other disk activity occuring at the
> same time.
>
I'll second that. It's not *too* slow... I'd say 5-10 minutes on
a 2-3 gig, 1-hour capture. That's certainly acceptable if it's scripted.
> Haven't played much with the CLI yet as my video processing is not
> done on my myth box, but this may now soon change if a suitable
> demux/edit/remux combo is found.
>
>>
I haven't convinced myself that a simple byte offset ASCII file is
sufficient for a cutlist. If it is, I'd like to try exporting a cutlist
from mythtv to try GOPCHOPing.
-Cory
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
More information about the mythtv-users
mailing list