flv to avi audio sync issues

pmr2011 · Post by **pmr2011** » Thu Sep 25, 2008 1:34 pm

Okay, I'm trying to convert an flv movie to avi (xvid/mp3). The file converts but ends up with a major audio lag that is barely noticeable at the start of the video but gets progressively worse until it's several seconds (and highly noticeable) after about the first 40-50 minutes.

My belief--and if anyone has an alternative theory please tell me!--is that the problem lies in the converted video's frame rate--the original video is at 24.97 fps but no matter what I do the outputted video is forced to 25.00 fps, which over the course of a 90 minute movie equals about 5-6 seconds of difference by the end, which is about what the lag seems to be. I've tried tampering with every relevant setting I can but nothing works; the end product is still at 25 fps even. I tried again with an audio delay of -400 ms but all that did was reverse the delay, putting it out of sync at the beginning of the video instead of the end.

Does anyone know why mediacoder refuses to encode my video at the original 24.97 fps instead of 25.00? I suspect that if I could get it to do that it would fix the problem. And if mediacoder can't do it is there a free program that CAN?

For the record...
*MC version: 0.6.1.4190, Windows XP SP3
*Source: MPlayer
Encoder: FFmpeg and MEncoder (haven't tried any others yet, neither of these worked.)
*Frame rate box is checked, set to either 24.97 or original (but unchecking it doesn't do anything.)
*"Force setting frame rate," "Do not skip any frame," and "Do not increase frame rate" options have all been tested unsuccessfully.

The video was downloaded from megavideo. File is ~300 mb, 4995.8 seconds long pre-conversion; after converting it's slightly larger (same bitrates) but only 4989.8 seconds, 6 seconds shorter than it is at 24.97, exactly as expected. Why mediacoder can't encode to 24.97 fps is beyond me btw...

Placio74 · Post by **Placio74** » Thu Sep 25, 2008 3:28 pm

It's probably VFR (variable frame rate).

Give me link to source video.

pmr2011 · Post by **pmr2011** » Fri Sep 26, 2008 1:27 am

The video source is here: http://tinyurl.com/3nrpl6
The original video page is here: http://tinyurl.com/3zr5z2 (through surfthechannel.com)

Interestingly, when I put the source url into mediacoder it reads the original video as having a frame rate of 25.00 fps, not 24.97. I'll try converting it directly from the source this time; it might take awhile (unreliable, often slow internet connection) but maybe it'll help. I'll keep you posted, assuming I don't have to wait a day and a half for the video to download!

Update: Downloading and converting directly from the source didn't work; the lag is still present in the encoded video. Incidentally, the conversion speed got progressively slower and slower while encoding even though my internet connection speed stayed fairly constant, which was a little frustrating.

Placio74 · Post by **Placio74** » Fri Sep 26, 2008 6:21 am

When transcode FLV's (with VFR)...

MPlayer or MEncoder as Source = possible out of sync A/V
FFmpeg as source = OK

However actual can't use correctly FFmpeg as source - no problem in older MediaCoder builds.

At this moment transcoding FLV with variable frame rate, it's not good idea (exclude some older builds).

Waiting for fix bug...

pmr2011 · Post by **pmr2011** » Fri Sep 26, 2008 6:34 am

I see what you mean. Using FFmpeg as the source would work, but there's a bug keeping MC from converting flv with FFmpeg as the source (I can't get it to work either.) Hopefully the next build will fix this bug! Thanks a lot placio, at least I understand what's going on now.

pmr2011 · Post by **pmr2011** » Sat Sep 27, 2008 9:08 am

Thanks mixer, but that's not the issue. It starts off okay and gets progressively worse and worse until it's several seconds off by the middle-end of the movie. Adding an audio delay just reversed the lag.

sclinac · Post by **sclinac** » Sun Sep 28, 2008 6:09 pm

Deleted Content by Moderator due to Spam and commercial software.

Note: If you continue to do this, you will be banned--moderator

pmr2011 · Post by **pmr2011** » Fri Oct 03, 2008 1:44 am

Just to keep y'all updated (and to bump the thread

), build 4095 has NOT corrected this, I still get error code 011 when trying to convert flv videos using FFmpeg as the source and encoder. Will try using an older build, see if that works better.

m-p{3} · Post by **m-p{3}** » Thu Feb 26, 2009 11:25 pm

Looks like I'm not alone with this problem.

I also get gradual sound out-of-sync issue. Putting a time offset doesn't fix the problem.

m-p{3} · Post by **m-p{3}** » Sat Feb 28, 2009 5:47 am

from "jalad pitt" frankly speaking, this is the third message i am going to post in this forum today. and seems that my answer is the same:-) This question actually still concern about conversion from one video format to another. and i noticed this time it's the sync issue between audio and video. (SPAM, rest of content deleted, user banned, admin)

Tried it in Sandboxie (I don't trust closed-source softwares), same out-of-sync problem. Also, not interested to purchase anything that I cannot openly tweak for myself the way I want. That is the whole point of MediaCoder.

And by the way, I'm posting here to fix the problem within MediaCoder, not to be redirected to another software. If we don't do this, the software will never make any progress.