SVCD data rate & muxing problem with bbMPEG

[jp1234]

Hello, I am trying to create an SVCD compliant MPEG file from an AVI capture file.

The video file is processed through CCE 2.64 and TooLame processes the audio at 224 Kbps.

Now when I try to mux the two streams together for the final file, bbMPEG says something similar to "mux rate too low. Look out for PTS/DTS underflow."

Since this is my first SVCD, I am not sure what the reason is. I don't want to create something that is out of spec, and I understand that the data rate has to be lower than 2600 Kbps at all times for this.

I have tried to reduce the video data rate in CCE, but it doesn't seem to have any effect on the warning in bbmpeg. My original idea was to create one disk with two TV shows of about 22 minutes each. With my initial settings in CCE, I got an MPV file of about 365 MB. After bbMpeg complained as above I tinkered with the settings in CCE (see below for my current settings) and got the file size down to 310 MB.

Am I not changing the CCE parameters enough or does it have anything to do with the audio? Any other suggestions?

My current CCE settings are Q=55, One-pass VBR, Min bitrate=800, max=2496, Image quality priority=25, Quantize Matrix Preset="Ultra Low Bitrate"

Incidentally, I am using bbmpeg version 1.24 beta 18, but once I start the program, the About dialog says its V 1.24 beta 13.

Thanks for any help

[wrestleantares]

The correct values for SVCD are pack size = 2324 and mux rate = 2,788,800

Word on Muxing SVCD - and on playbacktroubles in general:

When capturing to SVCD with default SVCD-template of 2400kb/s videobitrate and 224kb/s audiobitrate - you might sometimes experience VERY short peaks up to about 3000kb/s. And you might ask yourself if this is not a problem since the SVCD-specs states a maxbitrate of only 2600kb/s ? Will it not cause my SVCD to stutter in my dvd-player ?

Well - no it wont - actually its a very common mistake to focus exclusively on max bitrate when creating compliant svcd. What is really much more important is muxingrate and packetsize. No encoder - software or hardwarebased is capable of keeping precisly within the max bitrate you specify, not even the DVCII. But this is not the biggest problem in itself - most modern standaloneplayers are capable of handling these very short peakbitrates within reason - the biggest problem is that most softencoders do not encode using the right muxingrates and/or packetsizes for SVCD - and this is mostly what is causing playbacktroubles like stuttering and breakups in video with ugly big green blocks sometimes even with peakbitrates lower than those of the DVCII. The DVCII however DO encode using the correct muxingrate and packetsize which is why a SVCD created with the DVCII will play correctly on 99% of the players even if the peakbitrates is close to 3000kb/s.

The correct values for SVCD are pack size = 2324 and mux rate = 2,788,800

Now the muxingrate is closely tied together with the datarate - this means that IF the peakbitrate much exceeds about 3000kb/s - the datarate WILL get to high for the standard SVCD-muxingrate to handle - and this will cause playbacktroubles - even if you do have a player capable of playing files with higher bitrates. The cure for this is simply to demux the file and mux it back together using BBmpeg setting the muxingrate to 0 - this will force BBmpeg to calculate the needed muxingrate to fit the datarate. The muxingrate will get higher and will nolonger be 100% SVCD-compliant - but it will make the file play correctly. This cure can also be used if you have older SVCD-files created with softencoders that are giving you playbacktroubles.

Please note however - that there are still limits to what bitrates can be used. Different players have different cappabilities in handling bitrates - some players may be able to handle almost any bitrate, while others may play fine with peaks at 2600 but immediately start breaking up with peaks at 2700 - muxingrates cannot ovecome these barriers - so you will have to try and figure out what peakbitrates your specific player can handle.

[jp1234]

Thanks for the precise reply. You have no idea how much I googled all over the web and usenet to find an answer.

My pack and forced mux rate (taken from bbmpeg's SVCD settings) are set as you mentioned.

My DVD player's broken at the time, so I can't check what I encoded.

Just finished checking the peak & avg bitrates with bitrate viewer - peak=2549, avg=1931. Pretty good for my my 1st SVCD (although I encoded it over 4 times by now)

Thanks again for you help!