MP3 muxing and Delay values question

[1Stein]

Hi there,

I got a question which concerns only a few ms... you guessed it: it's about adding the audio to video. I reckon it can be best answered by somone who knows the ins of GKnot and Nandub and how exactly they work, though of course all input is very welcome :-) If I've overlooked the topic on the board please accept my excuses and be so kind to point me where I have to look. Thx.

Here's my scenario: I use GKnot to encode DivX5.0x...

In the first step I encode the two audio-streams (ususaly the language the film was shot in and my local language) to two 128 VBR-mp3's.

I then add the larger of the two to the bitrate calculator in GKnot and start another encoding step for the movie (trimed main movie and credits) and let the larger mp3 file be added in the process through GKnot.

As I want a second CD with the other language I've setup GKnot to NOT delete the intermediate files. You get the drift: Add credits to main movie with VDub, then add second mp3-file to the resulting movie using NanDub. Voila I have a second CD with the other language.

Here's my question: when there's a Delay value to set for the audio stream, it can be set the first time in GKnot when I do only the audio encoding. Later in the second step when I do the video encoding in GKnot and tell it to mux the mp3 file in the process I can set the Delay value again. Same in the third step when I mux the mute movie and the second mp3-file in Nandub: again the Delay value can be set. So do I

a) have to set that Delay value only once when encoding the audio streams (and leave it a 0 when muxing audio and video),

b) only once when muxing audio and video (and set it to 0 when encoding the audio) or

c) do I have to set the Delay value both times when encoding and later when muxing?

Wouldn't the c) scenario lead to the Delay being considered twice and thus being too large?

Thanks to everyone who can help.

Dunno if this is the right place. But I'd like to thank this anybody who's involved increating GKnot and the programs it contains. Great stuff!!!

Cheers

PS: unrelated (more or less) question. I noticed that when following the above process with Nandub the resulting avi files sometimes come with VBR mp3 audio and sometimes with CBR mp3 audio even though I always use the same settings. How come and is there a downside to either?

[jggimi]

Audio transcoders (LAME/Azid/BeSweet) don't have anything to do with delay. Gknot passes the delay value to Nandub for final mux. When interleaving by hand, enter the delay value in the audio interleaving window. If the delay is negative, which is an advance, enter the value as a negative number.

The delay (or advance) value is taken from the filename, assigned by DVD2AVI when you demux the audio track from the .vob stream. Gknot keeps the file name when encoding .mp3 streams. The value is used by Gknot when it uses Nandub to interleave audio files (.mp3 or .ac3) with the completed DivX video (_movie.avi and optionally _end_credits.avi).

So an "audio only" Gknot job doesn't use the entered delay value.

I do multiple audio tracks, too, but I prefer having both tracks on the same set of CDs. When I do 2-audio encodings, though, I'll usually do at least a 2-CD encoding, unless the content is very short (such as a featurette).

I can't answer why you seem to get CBR audio. It's not recommended for movies, since there are often many areas of silence in movie soundtracks.

[1Stein]

Thanks a lot for the quick reply. No prob on the muxing front anymore :). Just hope this CBR vs VBR problem doesn't re-occure or I'll have to bother you again. Thanks again for the quick help -- wish I could give something back... maybe when I've learned a bit more about all this.