Any problems with setting forced mux rate to 6972?

andy

When I make SVCDs with video 2500 CBR + audio 224 the first couple or few secs (and when I skip forward using chapters) provide distorted audio (and a touch of video jerkiness)...the sort of thing you'd expect when you exceed your player's bitrate limit. The rest of the film is fine though. I've just been using 10 sec overlap

Anyway I decided to figure out what was doing this, and it turns out it doesn't happen if the mux rate is 6972 - the SVCD spec default. Only tried it with a 1 min sample btw.

Now as the bitrates I'm using are within SVCD spec, is it the case that there's absolutely no disadvantage to me setting the mux rate to 6972? From the search feature I understand that the use of 0 is only purposeful when the bitrates are greater than spec.

Thanks

edit: tried muxing a 3 cd film and got one underflow error on the second file. Presumably due to the inaccuracy of CBR (i.e. bitrate above svcd spec at a certain point in time). Guess I'll just live with the distortion, it's no huge deal.

Hi Matthew,

shouldn't be a problem setting the forced muxrate to 6972 as it is the default setting for SVCD MPEG2 streams. I did quite some testing on that subject in the past as the drive of my DVD player is sometimes a little picky. And sometimes indeed the movie playback was slightly better especially at the beginning - the same effect you were experiencing during your testing.

But I never had any under/overflow errors with a muxrate of 6972 yet - but this depends on the movie, your audio bitrate and your bitrate settings also. But only one underflow error is not bad at all and chances are good you will not see this glitch at this stream packet in the end.

With the automatic setting of 0 bbMPEG tends to use a very safe muxrate for the stream you can try to tame it a little bit by setting the quot;Computed Bitratequot; to quot;Use Avgquot; - this should result in a slightly lower muxrate than the quot;Use Maxquot; setting in the end. TMPGEnc for example tends to create streams with a lower muxrate from the same material than bbMPEG does.

In the end it's all testing.

Hope this helps,
Gerti

Thanks gerti

In regards to the film I got an error on, well I tried muxing it again and there were no overflow errors

I think what I'll do is stick with 6972 unless there are overflow errors - but the problem is that there's no way to tell this without sitting there watching bbmpeg is there?

My solution is to leave the DVD2SVCD bbmpeg setting at 0. When it's done I can run the following batch files simultaneously (for a 3 cd film).

@echo off
del H:\bbMPEG1\default.ini
copy quot;bbMPEG Movie Settings1.iniquot; H:\bbmpeg1\default.ini
H:
cd\bbmpeg1
RunbbMPEG.exe quot;H:\bbmpeg1\bbMPEG_Muxed_File.mpgquot;

@echo off
del H:\bbMPEG2\default.ini
copy quot;bbMPEG Movie Settings2.iniquot; H:\bbmpeg2\default.ini
H:
cd\bbmpeg2
RunbbMPEG.exe quot;H:\bbmpeg2\bbMPEG_Muxed_File.mpgquot;

@echo off
del H:\bbMPEG3\default.ini
copy quot;bbMPEG Movie Settings3.iniquot; H:\bbmpeg3\default.ini
H:
cd\bbmpeg3
RunbbMPEG.exe quot;H:\bbmpeg3\bbMPEG_Muxed_File.mpgquot;

I can look to see if there are any error messages as 3 copies of bbmpeg will be open even when the muxing is finished. If there are errors I can use the DVD2SVCD cd images. If not I will substitute my mpgs for those in the DVD2SVCD directory and run crash recovery from quot;SVCD Authoringquot;.

Not really much extra effort at all really

BTW I tried setting the quot;Computed Bitratequot; to quot;Use Avgquot; and got a whole lot of errors, so I cancelled the muxing.