Avi to DVD and Audio Sync Issue

[macbuz]

I've searched the forums and found similar issues as I am having but .... well, not sure if I have read the answer or not. The avi file plays fine in VLC or QT, there's no sync issue. After encoding the dvd file has that creeping, ever increasing sync issue. This has occurred on two files now.

From what I've read I don't think I have a hardware issue, should have plenty of 'poop' to manage these encodes. It could be that I have had other processes going while encoding that perhaps taxed things to far. Then there's the possibility of the video bitrate being too high. This is certainly a possibility with the last encode where I 'cranked' the video bitrate.

I intend to re-encode these making adjustments i.e. - maintain a lower video bitrate and stop other cpu intense processes in the back ground. For the most part I accept the default settings except for ticking the 3:2 pulldown if necessary and making sure Author as Video_TS is ticked. Both are mpeg4, ac3 formats encoding to mpeg2, ac3.

Are there other settings that may help solve the sync'ing problem?

[John-Paul]

From a quick glance at your other post (https://forum.videohelp.com/topic362189.html), it seemed that you were having framerate issues. If your source avi is 25 fps and you're converting to NTSC DVD my suggestion would be to extract and process the video and audio separately, changing the framerate and audio duration to the equivalent of 23.976fps. Then encode/author with pulldown.

With a 23.976fps .avi, author to DVD directly with pulldown.

If you encounter a 29.97fps .avi, simply author to DVD.

The first step should always be view the video file info in Gspot, Media Info or similar.

[macbuz]

Yes, my issues are more along the lines of being fairly new to encoding and being in the learning curve. Am getting my head around the framerate issues. Your pointers to 23.976 + pull down = author and 29.97 = author are simple and straight forward.

I have MediaInfo now - how nice. I'm curious, when I drop a file on Ffmpeg and it fills in the blanks, should that data be checked against MediaInfo data to make sure they match?

Edit: The reason for the above question is this: Ffmpeg > Summary LCD says Audio bitrate is 192, Ffmpeg > Audio Tab has the bitrate at 448 and Media info has the bitrate at 192. So for some reason, when the file is dropped on Ffmpeg it construes the Audio bitrate at 448 instead of 192.

Could this be the cause of the sync'ing issue. Gonna encode again with this change and see what happens.

[tomlee59]

The audio *tab* shows the target bitrate of the file you produce, not the bitrate of the source. The Summary panes in ffmpegx tell you what ffmpegx believes to be the characteristics of the source.

The creeping sync problem is very common, and not always readily fixable within ffmpegx. If the error starts at zero, and ends up with the audio out of sync by about 3.5 seconds per hour of video, then properly selecting pulldown will likely fix it. In other cases, selecting "decode with QT" will help. If you haven't tried these, give them a go.

In most cases, however, the sync drift rate is about a third of the value above. In my experience, if "decode with QT" won't fix it, nothing will. Here's what I've done in those situations (besides using PC-based tools). Carefully note the offset throughout the movie to verify that the drift is truly linear. Compute the difference in offsets between that at the beginning, and that at the end. This number is the amount by which the audio needs to be shortened/lengthened. Use a tool like Audacity (free and powerful), whose Adjust Tempo effect allows you to alter duration. Accuracy is important; a 50-100ms error is noticeable and 200ms is intolerable.

[macbuz]

Thank you. I've encoded this maybe 4 times now experimenting with different settings. Each time it has been with pull down and decode with QT set in the options tab. Wondering about the constant bitrate in options, CBR is selected in the audio tab, should it also be 'ticked' in the options tab?

For a 'hobbyist' I may be starting to get in over my head, but I'm going to continue cause I like challenges sometimes and perhaps if I'm able to manage this in the end .... well ..... I'll continue with my project.

I have Audacity downloaded, took the 1.3.6 beta. I see there is support for import / export with Ffmpeg.

My biggest problem is going to be the fact that this is an animated movie so sync'ing is very hard to 'pin point'. At any rate I'm off to see what I can do with Audacity.

<laughing at myself> ...... (Maybe Audacity has a forum) - how do I get the audio to 'work with'. Assuming I need the 'corrupted' file from the DVD file - take it out, fix it, put it back??? Or do I split it out of the avi file, fix it and recombine? Kinda lost if it isn't obvious.

[macbuz]

I've been encoding to my desktop and just remembered that besides the dvd file there are three other resulting files from the encode - is it one of these that I use in Audacity? Seems the m2v, ac3 and mpg files are selectable to import to Audacity - guess I'll 'mess' with the ac3 file for starters and see what happens. Need to somehow figure the 'offset' from beginning to end - how much it lags.

Thanks a million though for the pointer here.

[macbuz]

I may well be way over my head here. Having trouble pointing Audacity to the library files. I have downloaded and installed them. In Audacity prefs when it asks for location of avformat-52.dll I paste in /usr/local/lib/audacity/ just ahead of it and it fails. I noticed however that the file in /usr/local/lib/audacity is actually avformat52.dll .... without the hyphen. Can I just delete the hyphen in the /usr/local/lib/audacity/ directory?

[macbuz]

Still trying to get Aud to locate lib files .... in the mean time though I'm wondering about MediaInfo data regarding video length and audio length.

Video Stream Length -> 1h 17mn 58s 428ms
Audio Stream Length -> 1h 17mn 58s 387ms
Audio Stream Delay -> 1s 250ms

Do these values mean anything in regards to sync'ing? The values come from the avi file that is used to create the dvd file so my pea brain says the avi file would also show the issue, but it doesn't.

[tomlee59]

Re: pinpointing. Often the most accurate readings come from discrete events, like explosions, door slams, etc.

As to Audacity, I don't know what that is all about. I just download Audacity, point it to the Lamelib (for MP3 encoding only; you don't need that here), and it's good to go. Perhaps you ought to download the stable version, not the beta. Could be there's some oddness in that latest build. Betas are not good choices for someone who is starting out. Too many sources of problems!

Feed the audio stream into Audacity. If you have it lying around, great. If not, demux your (badly sync'd) track, and feed the audio stream to Audacity.

[macbuz]

Re: pinpointing. Often the most accurate readings come from discrete events, like explosions, door slams, etc.

I have bookmarked a few spots in the movie with video/audio that will have the best chance for me to 'see' the sync stage. Again, this is an animated show and, well, while very good animation, leaves a little to be desired at this detail level.

As to Audacity, I don't know what that is all about. I just download Audacity, point it to the Lamelib (for MP3 encoding only; you don't need that here), and it's good to go. Perhaps you ought to download the stable version, not the beta. Could be there's some oddness in that latest build. Betas are not good choices for someone who is starting out. Too many sources of problems!

Reading my mind on this - thot I would give the beta a go but it does seem much less than ready for prime time.

Feed the audio stream into Audacity. If you have it lying around, great. If not, demux your (badly sync'd) track, and feed the audio stream to Audacity.

When I encode the avi file I wind up with four files on my desktop (default location to encode to for me), there's the dvd file, and an m2v, ac3 and mpg files as well. Can I just use the ac3 file and then mux it together with my dvd?

[macbuz]

Audacity has an alpha build now that I am using, found the ffmpeg libraries np. From an earlier post of mine >>>>

Video Stream Length -> 1h 17mn 58s 428ms
Audio Stream Length -> 1h 17mn 58s 387ms
Audio Stream Delay -> 1s 250ms

...... are these significant to my sync problem? It is MediaInfo data from the avi file?

[tomlee59]

That collection of files is a superset of what you need to produce a dvd, to faciliate use with different authoring tools.

You can operate directly on the ac3 file, if you wish. Just check to make sure that it's complete. If you export the result in mp2 form (48kHz sampling rate), and mux that with your m2v, the resulting mpeg will generally be acceptable to authoring tools.

As to the delay information, etc., provided by your avi tool, ignore it. It will be of little or no help in determining the numerical values you need to fix up sync. That ~40ms duration difference is interesting, but too small to be problematic. That fact that you are noticing a sync problem indicates something more needs to be done.

[macbuz]

Ok guys ... you've been super and I need a little more .....

I found a timer i could use to figure my sync error and it looks like the error is same from beginning to end, around 1.25 - 1.5 seconds. The range is relative to my 'aged' clicking ability. The audio is ahead of the video e.g. speech ............. then action.

Am I correct in thinking that to fix this in Audacity, if I add 1.25 seconds to the front end of the audio, in effect delaying it's start, it should line up better with the video?

First I mixed and rendered the six tracks, then I used the time shift tool to move the audio tracks ahead 1 second. Rendered again and export as mp2 file. Muxed the m2v and mp2 files and mux failed .........

INFO: [mplex] mplex version 1.9.0 (2.2.7 $Date: 2006/02/01 22:23:01 $)
INFO: [mplex] File /Users/buz/Desktop/*******.(2008).DVD.m2v looks like an MPEG Video stream.
**ERROR: [mplex] File /Users/buz/Desktop/*******.(2008).DVD.mp2 unrecogniseable!
**ERROR: [mplex] Unrecogniseable file(s)... exiting.

Enough info here to tell me what I did wrong?

Edit: I tried muxing again this time as a mpeg-2 and it failed again.

[tomlee59]

I think you're almost there -- you're to be commended for sticking with it!

The muxing failure could be caused by several things, some easy, some hard. Let's try the easy stuff first. Some muxing tools are needlessly fussy about the file extension. Try changing xxx.mp2 to xxx.mpa and see if you can successfully mux. If still no joy, we'll go to Plan B.

[Herve]

INFO: [mplex] mplex version 1.9.0 (2.2.7 $Date: 2006/02/01 22:23:01 $)
INFO: [mplex] File /Users/buz/Desktop/*******.(2008).DVD.m2v looks like an MPEG Video stream.
**ERROR: [mplex] File /Users/buz/Desktop/*******.(2008).DVD.mp2 unrecogniseable!
**ERROR: [mplex] Unrecogniseable file(s)... exiting.

Enough info here to tell me what I did wrong?

I suppose you used an out-dated version of FFmpeg to encode audio to mp2 (an old version of FFmpeg had this "bug": it tagged mp2 files as mp3 -same family but non compatible with mplex)
just encode to ac3 (instead of mp2) and mplex will accept to mux

bye

[macbuz]

Yes that worked thank you.

My version is ffmpegX v0.0.9x r2 Sep 28, 2006 - is there a more recent version I should be using?

EDIT: Nevermind, I found .9y - hoping this may improve my track record a bit

[macbuz]

Finally, persistence pays. Your help, some help from the Audacity forum and it is fixed. At least it's much much better. Not going to say it's perfect, but certainly acceptable.

Got a 1.3 second sound clip added to the front end and it's just enough ... hard to imagine getting the sync within the <200ms suggestion, must take a microscope.

Is there a utility that can help 'measure' these sync problems?

Thank you all very much. Successes come so slowly/rarely.

[tomlee59]

Well done -- congratulations!

I don't know of any tool that would automate the process much. To determine the sync errors, I use VLC, which has the ability to alter the sync by amounts you specify. Through a little trial and error, you can figure out the necessary numbers to acceptable precision without too much labor. A bit clunky, yes, but it gets the job done.

There are other ways to achieve the same thing. Mplayer, for example, allows you to increment/decrement on the fly while playing (which VLC does not).

Congrats again!

[macbuz]

tomlee59 ....

Hmmm, I'll have to look closer at those two apps. Do they 'just' help determine the sync error or do they 'repair' as well.

... and congrats to you as well for persistence in pushing this hobbyist through.

BTW - I no sooner got the mux'ing done, and checked, ready to burn and the door bell rang - FedEx with my new Taiyo Yuden 8x DVD-R's. Timing couldn't have been better.

[Herve]

My version is ffmpegX[...]

I said ffmpeg (the biggest video library) not ffmpegX (just an application)

Mplayer, for example, allows you to increment/decrement on the fly while playing (which VLC does not).

VLC does it
launch your video file, play with keys "f" and "g" (on my french keyboard, I don't know with us) to change audio sync (negative or positive values are allowed). And report them to audacity…

bye

[macbuz]

I suppose you used an out-dated version of FFmpeg to encode audio to mp2 (an old version of FFmpeg had this "bug": it tagged mp2 files as mp3 -same family but non compatible with mplex)
just encode to ac3 (instead of mp2) and mplex will accept to mux

bye

Can anyone tell me how to check my library for, if it's latest or not. I believe it should be, I recall the process involved 3 other files to install separately and recall some difficulty in finding them.

[tomlee59]

My version is ffmpegX[...]

I said ffmpeg (the biggest video library) not ffmpegX (just an application)

Mplayer, for example, allows you to increment/decrement on the fly while playing (which VLC does not).

VLC does it
launch your video file, play with keys "f" and "g" (on my french keyboard, I don't know with us) to change audio sync (negative or positive values are allowed).
bye

Je vous remercie de nouveau, Herve!

--Tom