Encoded a VBR-SVCD and the mpg2 file is fine with regard to

[jeremymiller]

video/audio sync on the PC. However, after burning with Nero and played it on a DVD player, the video/audio is slightly out of sync. I wonder if it is a file conversion problem or some other issues. For those SVCD creators out there, have you encountered this problem? How do you correct the problem? Thanks,

Jeremy

[adam]

Most audio sync problems on your hardware player are caused by improper multiplexing. From my experience, TMPGenc does not do a very good job multiplexing mpeg2, and for some reason this problem is even worse when you encode audio and video together rather than multiplexing in the end. In any case, TMPGenc does not support SVCD scan offsets which is used by nearly all dvd players to maintain sync during playback.

Try using bbmpeg to multiplex your mpg. If you have a program stream (mpg) you will first have to demultiplex (TMPGEnc's mpeg tools/simple demultiplex,) so for conveniance's sake its best to just encode your video and audio separately in the future. BBmpeg can be found in the tools section and a guide can be found in the EDIT section. Just follow the bbmpeg cutting guide and ignore the part about cutting and it shows how to use its multiplexing functions.

The default SVCD template will use SVCD scan offsets, which may solve your sync problems. If any PTS underflows occur during multiplexing then remultiplex with a forced mux rate of 0 (automatic.)

[jeremymiller]

Thank you so much. I will sure to try it. Those who have similar problems should give it try also.

[Martyn1980]

Adam i have a problem using BBmpeg to mulitplex, most of my stuff is 4or 5 pass VBR with a min300 max4000-6000, depends on the source, and if i use BBmpeg to mulitplex, it works fine on the PC but in my DVD player its extremely jerky in anything high action, when the bitrate obviously must be hitting the max, but if i use Tmpeg its perfect, although i have had one out of sync film using it, but it was tiny and i was the only person who could see it.

Am i missing some settings in BBmpeg, cause ive tried everything and it still does it, does BBmpeg not like high bitrates multiplexed as a SVCD or is it just the DVD player.



P.S. So thats what SVCD Scan Offsets is Fit CD says you dont need it, but doesn't say what it is or why you dont need it.

[kwag]

Do NOT use SVCD scan offsets in a SVCD stream. There are no known firmwares or MPEG decoders that support it. Period. Read the Readme file included in FitCD and search the web on this topic for more information.

-kwag

[kinneera]

Putting the scan offsets in is not likely to cause any adverse effects.

As for bbMPEG, if you are encoding an XSVCD at bitrates up to 6000Kbps, the SVCD default settings will use a pack size that is too small and will probably cause substantial underflows.

[Martyn1980]

Thanks guys, thats kinda what i thought, but mulitplexing as a Mpeg 2 program stream will make the filesize appear bigger to SVCD authoring programs so do you recommed i stick with Tmpeg to mulitplex, 90% of the time it works fine with no audio sync problems.



1. Don't use SVCD scan offsets in a SVCD stream. No known firmware
and/or MPEG-decoder-chip even parses this [overhead].

You mean this bit, i have read it, thats why i was confused with what Adam said.

[kinneera]

A word of caution, I believe disc authoring software generally will look for the scan offsets in the stream to generate the scandata.dat file, which is used by firmware/decoders. VCDImager warns if it can't locate scan offsets, in any case.

If you are doing XSVCD, yes, you may have to stick with TMPGEnc unless you want to muck around with bbMPEG's settings. I think maybe bbMPEG restricts what you can do unless you're working with program streams, though. I recall not being able to get it to mux an XVCD.

[adam]

If you multiplex as a SVCD using non-standard bitrates this will certainly cause PTS underflows which often cause sync problems. Usually setting the forced mux rate to 0 prevents all PTS underflows regardless of your bitrate. In any case, use what works for you. In general, I do consider bbmpeg a much more compliant and better overall multiplexor than TMPGenc, at least for mpeg2.

Kwag there is certainly enough conflicting evidence regarding SVCD scan offsets thats its hardly advisable to simply say, don't use it ever. This is especially the case since the only drawback to using them is slightly increased filesize. Other than that they don't actually hurt anything and their function IS to maintain sync, specifically during seeking and there is evidence which supports this. I can only speak from experience on this matter. If I do not use SVCD scan offsets then jumping to a new chapter or resuming play after a ff or rw ALWAYS results in desync for up to 5 secs on my Apex AD600a and my Dad's Pioneer. With the SVCD scan offsets sync is maintained perfectly and instantly in both of these situations. In helping people sort out desync problems the inclusion of the SVCD scan offsets did solve their problems on several occasions. I can only conclude that the SVCD scan offsets DO, do something, at least on some hardware players. Shh (author of FitCD) is very knowledgable and I respect his opinions, however while his conclusions regarding SVCD scan offsets may be generally correct, I do not feel they are entirely correct. In any case you cannot draw an absolute conclusion based on the research and advice of ONE person, especially when there is a multitude of conflicting evidence and opinions.

Bottom line, the SVCD scan offsets may solve sync problems. Try multiplexing with and without them. If they help then great. If they don't help than don't bother using them.

[Martyn1980]

I think im understanding this now, if as you say and i believe it does, Create more comliant SVCD(BBmpeg) then this is probably the reason this is happening as what im doing is far from compliant.

As for the scan offsets, this explains why i get a smaller filesize when i use Tmpeg, and why when i change chapters, i loose sync for a second,if i put a chapter in the middle of a scene(which i rarely do anyway).

Thanks for the help in clearing things up guys, i think my options are drop my Max bitrate, or risk a little desync occasionally.

I think i'll stick with Tmpeg for now as i plan to put most of the stuff i do on DVD when i get a burner, so i want the quality as good as i can get it at the moment.