VBR vs. CBR

[richardofstvictor]

I've been learning to rip and encode movies into DivX 5. One my problems is that when I play a DivX movie encoded with VBR audio, the audio goes out of sync whenever I fast forward or skip ahead. Actually what happens is the video starts at the right place, but the audio starts from the very beginning. After I convert the audio to CBR I have no such problems.

This is what I do:
I encode using Gordian Knot following the DivX 5 guide on doom9. On audio part of the bitrate page I select either "1x ac3" or "1x vbr mp3," it doesn't matter because it has always come out VBR. In the DivX encoding page I check "mp3."

This creates an avi file with VBR. Then after I have created the avi, I have to go back, save the wav and then re-encode the avi with CBR mp3 using virtualdub. But it makes the file, once just the right size to fit on 1 CD, too big.

Questions:
1. Why can't my players (DivX player 2.0 Alpha, Win Media Player) play files with VBR? How do I get them to do so? Or should I get another player?

2. Can I encode directly to CBR using GKnot? Or is there a quicker way to convert the VBR AVI to CBR?

3. Is there a guide describing in fuller detail the audio options in GKnot? Like what is "mux?" And what are the settings to retain DD 5.1 sound?

Thanks in advance!

[theReal]

On audio part of the bitrate page I select either "1x ac3" or "1x vbr mp3," it doesn't matter because it has always come out VBRThis is only for the filesize calculation (the overhead is different). Only set it to AC3 if you're using AC3, or the bitrate of your movie will be wrong (might be enough to make it not fit on a CD anymore...).

To encode the audio to CBR in Gknot, choose the expert-mode and enter as Lame-parameters: "--alt-preset cbr 128"

Encode, ready!

I don't know what the problem of your mediaplayers is - all I can say is that I'm having the same problem with BSplayer. It just runs out of sync with VBR and ABR mp3. Mediaplayer 6.4 is doing fine, though.

[richardofstvictor]

Originally posted by theReal


To encode the audio to CBR in Gknot, choose the expert-mode and enter as Lame-parameters: "--alt-preset cbr 128"

Encode, ready!

I don't know what the problem of your mediaplayers is - all I can say is that I'm having the same problem with BSplayer. It just runs out of sync with VBR and ABR mp3. Mediaplayer 6.4 is doing fine, though.

Thanks for replying!

I tried using those codes in G-Knot but it still came out as VBR. I opened it in VirtualDub and it said VBR error... yada yada yada. So I had to save the AVI again to get it right. Am I still missing something?

[theReal]

You don't have to encode the avi file again - only encode the audio and then mux (=combine) it with the video as soon as everything is correct.


Try to set the audio encoder tab like this:
http://www.computerfuzzies.de/temp/gknot.jpg
(of course you can use another bitrate than 128kbit, I just assumed you wanted to encode the audio at 128. Better don't go below 112 though).
Then hit the "Add Audio Job to Encoding Queue (No Video!)" Button.

The mp3 should be ready in about 20-40min, depending on your cpu and stuff. Then you can check if it is right, sounds right and if the size is ok to match with your already encoded video. If it is, use Nandub to mux video and audio (I think this is described in the guides somewhere).

P.S.: I always encode the audio before the video to see if everything is ok and if it sounds good, then I encode the video without audio and mux both in the end.