Audio sync, (DivX, XviD) cut/merge re-encode

BoardinGar · Post by **BoardinGar** » Wed Aug 22, 2007 6:24 pm

I am having major issues with audio sync when I convert DivX or XviD to DivX or XviD. I know that these are highly compressed files and are not made for decoding and recompressing on the fly. Sometimes it works fine, and others it is seconds out of sync. I have split the streams(vid/aud), lengthened some, shortened others, but that process is very time consuming and I did not get it to work many times.

I am cutting these files(DivX,XviD), inserting other clips which could be in any format(currently mpg, but I've tried using avis also, same problem), and then I am re-encoding them. Is the only way to convert to mpg first? Would that fix the sync issues? If I was OK with a little loss in picture quality what would be the best solution for me? I also don't want the process to take a day to complete, but a few hours is fine!!

I would greatly appreciate any suggestions. Thanks

nmehta · Post by **nmehta** » Wed Aug 22, 2007 7:07 pm

Hi BoardinGar,

I am not sure if the following videos tutorial directly addresses your problem but it may help:

http://takeoneflix.com/ulead-videostudi ... high-gear/

Regards

Neel

Edit by sjj1805 - Web Board Administrator 26 Feb 2009.
When this post was created the video tutorials mentioned were all free.
That has now changed and members are advised that they have to be purchased. I must point out that these links are only provided for the purpose of convenience to our members. Neither Corel, the Forum Management or myself endorse any of the products listed and I/We have no associations with the vendors of any software listed below. I/We do not guarantee the quality of any of these products or their compatibility with the Corel products they are designed to work with. I/We will not enter into any negotiations between Members and the Company providing these tutorials.

BoardinGar · Post by **BoardinGar** » Wed Aug 22, 2007 7:26 pm

Hey thanks for a reply. I had not seen that tutorial before, but I already knew most of the stuff on there.

There wasn't anything on decoding or getting the audio in sync though!! Any other thoughts? Thanks

DVDDoug · Post by **DVDDoug** » Wed Aug 22, 2007 8:10 pm

I am having major issues with audio sync when I convert DivX or XviD to DivX or XviD.

If you get sync problems symply by converting (without any editing), your DivX or Xvid file is corrupted. I don't know of any programs that can repair DivX/Xvid files, but you may be able to find one. (VideoReDo and Womble have tools to repair MPEG-2 files.) If you can find a repair tool, the idea would be to repair the file before converting it... The resulting out-of-sync file is probably not corrupted.*

You could also try a different conversion program. SUPER is FREE!!!

I am cutting these files(DivX,XviD), inserting other clips which could be in any format(currently mpg, but I've tried using avis also, same problem), and then I am re-encoding them. Is the only way to convert to mpg first?

Editing these highly-compressed files can cause corruption that shows-up as sync problems, or worse. The same problems sometimes show-up when editing MPEG-2. (I bought a special-purpose MPEG editor from Womble because of this.) You may need to find a special-purpose DivX/Xvid editor... if one exists...

I think your best bet is to convert everything to AVI/DV before editing. (AVI/DV files are 13GB per hour.) The more compressed the format, the more likely you are to run into trouble. MPEG-2 sometimes causes trouble. DivX and Xvid (MPEG-4 variations) seem to cause lots of trouble. (Note than not all AVI files are DV encoded. AVI is a container format, and it can contain any type of compression from DV to DivX.)

If I was OK with a little loss in picture quality what would be the best solution for me?

There will always be some quality loss when converting from one lossy format to another. These are all lossy compression methods, and you loose some quality everytime you compress. The video has to be de-compressed before it is re-compressed to a new format. Most editing also requires the video to be de-compressed and re-compressed. If the quality loss is noticeable or not depends on many different factors.

The conversion to AVI/DV should not create a noticeable quality loss, since DV is much less-lossy than the other formats. So, a DivX-to-AVI/DV-to-Xvid conversion should not look any different than a DivX-to-Xvid conversion.

I also don't want the process to take a day to complete, but a few hours is fine!!

A lot of people complain that it takes 8 hours or more to make a DVD from a DivX/Xvid file. Whenever you see a post about long render times, it's a good bet that they are using DivX/Xvid. If this happens to you, you might try a different conversion program.

I know that these are highly compressed files and are not made for decoding and recompressing on the fly.

These formats are not designed to be converted or edited at all! The same is true of MPEG-2 (the DVD format). The best procedure is to compress once to the final format after all editing is done. I'm not saying it can't be done.. but it can be a pain, and there is always some quality loss.

* Imagine that you have a bad (corrupt) video frame. If the bad frame gets thrown-away during conversion, but the associated audio remains, you've now got a sync problem. That may not be exactly what's happening, but it's an example.

BoardinGar · Post by **BoardinGar** » Wed Aug 22, 2007 9:48 pm

Wow, I wasn't expecting such a long, detailed response. You answered all of my questions and more. Thank you so much, I really appreciate it.