AC3 delay: is it possible to correct it without reencoding the audio file ?

[solvalou]

Stupid question here -- > So I have these 2 DVDs and I want to fit them in a 4.3 gb DVD-R media. I extracted the AC3 audio and video streams and recompressed the video stream. I know that for encoding a vcd/svcd/divx you have to correct the AC3 delay but in my case I want to author the DVD again. Do I have to reencode the AC3 file to correct the delay or can I just leave it like that and mix it again using DVDMaestro ?

If I have to correct the audio delay (in my case its -67ms) how can I do it without loosing audio quality (no recompression)??

any info will be greatly apreciated

[oddyseus]

-67ms means that audio is starting before video does. Since a video frame is 33.??? msecs in NTSC, this is 2 video frames exactly.

Obviously u cant shift audio beyond video in Maestro timeline only positive shifts r allowed, so what u can do is to use the Sync Audio feature of Maestro that would syncronize your video with your audio provided ofcourse that both of them r correctly timecoded. If both r form the same original, they r.

If u don't know how Sync Audio works, there r a few threads that deal with it and describing with details, that I believe is reduduncy to repeat here.

[SurfDrifter]

There is also another solution that is called "AC3 Delay Corrector" and you can download from the software section...

http://www.doom9.org/Soft21/Audio/ac3delay_all.zip

You enter the ac3 file with the delay and it cuts or adds (according to the delay) the amount of frames that are required...

[KpeX]

How about something like this:

besweet.exe -core ( -input "dvd.lst" -substream 0x80 -payload -output "audio.ac3" ) -ota ( -d auto )

Where dvd.lst lists your .vob files and making sure you have vobinput.dll in your besweet directory, also substitute stream 0x80 for whichever one you want. Or use a dvd authoring software solution like oddyseus suggested.

[Matthew]

My solution is to cut frames using ac3 delay corrector so the delay is positive then drag audio to right in maestro. ac3 delay correct by itself in innacurate, because 1 frame = 32 ms.

In this case -67 + 96 (cut 3 frames, each 32 ms) = +29ms. Then drag to right until delay is 29ms.

Or you could just cut 2 frames (64ms) and not worry about -3 ms delay :)

[solvalou]

Thanks for the tips guys !!! Really apreciate it.

Let me see if I get it right. Like oddyseus said, -67ms delay means that the audio (to be in synch) should start 2 frames before the video. correct ? To fix this -67ms thing I should cut the first 2 frames of my ac3 file and for that I need ac3delay_all.zip proggie.

When i set it to -67ms it will cut the first 2 frames right ? not the last 2. :) sorry for this stupid question , its just that when it finished the process i got this message

"2 frames (62ms) have been cut.
46232 frames (00:24:04,750) have been written.
Last frame was too short. Ignored.
There are 32 frames in one second."

Im worried about the >>Last frame was too short. Ignored.<< what does it have to do with cutting the first 2 frames ? :)

[Matthew]

The last frame too short is a separate issue. It just means the last frame was left off when AC3 delay corrector re-saved the AC3 file because it was a partial frame (often happens, say, if you have ripped up to the end of a chapter rather than the movie). Don't worry about it :)