adjusting audio (ms) - not a noob question

[ZiGGY909]

Hi There

I have converted a 23.976 AVI into a 29.97 MPV, I use CCE with a 3:2 pulldown.

Then I saved a uncompressed WAV from the original AVI with VirtualDub. But it's difficult to tell whether or not the audio is perfectly in sync, its pretty close but I really want this to be dead accurate.

My original audio is 1:55:31.39 (VirtualDub info)
My saved WAV is 1:55:31.008 (Nero Wave Editor info)

I need my outputted WAV to match the original. I have tried VirtualDub's Interleaving option by fiddling with the milliseconds, but it just wont work.

Am I right in saying "1:55:31.39" is "1:55:31.390" or is it really "1:55:31.039" ???

Thanks for any info, quite technical this is

[mh2360]

It could be that the audio length is fine, even though it's not EXACTLY the same as the video, it might be just out of sync.

You could experiment with cutting or inserting a few milliseconds to the beginning of the audio file.

Instead of having to edit/encode/remux a 2 hour audio file each time, you could just cut a 10 minute piece from the start of the audio and video files and experiment with these. This should tell you how much you need to add/cut from the final audio file.

It it then starts off in perfect sync, but drifts out later then its the audio length that's the problem.

[manono]

quite technical this is

Hardly. You muxed them already, right? And they seem to be in synch, right? If they were really 382ms out of synch, believe me, you'd know.

Am I right in saying "1:55:31.39" is "1:55:31.390"

Yes.

[ZiGGY909]

Thank You !!!

Yes, it does seem in sync, even though after extracting WAV it said I lost 382ms. But as you said, it must be correct because it looks good to me.

Is CCE the best app to use for 3:2 pulldown? (23>29). Or should I be using AviSynth script instead? (I do use AviSynth with CCE) If so, what command do I use for a 3:2 pulldown?

cheers guys, you have been great help

[Alex_ander]

Is CCE the best app to use for 3:2 pulldown? (23>29). Or should I be using AviSynth script instead? (I do use AviSynth with CCE) If so, what command do I use for a 3:2 pulldown?

Those 2 ways are different:

1)You encode just 23.976 frames per each second (with flags added for playback at 29.97) => bitrate is used more effectively. + If someone some day wants to restore progressive frames from your encoding, it would be easy to do.

2)This way you'd modify video before encoding by building extra interlaced frames that complement framerate to 29.97. Encoding duplicate fields used for this takes 20% of bitrate.

[TBoneit]

TMPGEnc Xpress 3 always shows me the audio length as different than the video more or less like what you are seeing and it plays in sync after encoding. Especially after extracting VBR to wave wity VdubMod.

I've always just assumed that the difference was at the end during the credit roll where it doesn't matter. I could also be wrong.

[Cornucopia]

Just to help ease people's minds about this "sync" thing, here's a little bit to remember (beware, it may UNEASE some people's minds):

ANY time Pulldown is used, there is motion judder. This also means that audio, which doesn't get pulled-down, won't exactly match the video during those pulled-down frames.

Note this example: 25 frames of a 24fps show = 1 sec + 1/24 sec = 1.04166666666 sec.
If this is "pulled-down", it's either going to be 31 frames (=1.0333333 sec.) or 32 frames (1.06666666 sec.)--this using 30fps (I won't even go into it if it's 23.976 & 29.97!).
The audio is still 1.0416666666 sec.

"The audio is out of sync", you say. Not really. It "corrects" itself every frame or two. And those who are used to pulldown mostly can ignore this slight shifting going on.

.............

Now, this may not clear up your mind about a piece of audio that "was a different length after extracting". This could be due to a number of factors, some ignorable and some not.

How does each app extract the audio? How does each app COUNT the audio? -- By Samples? By Frames (linked to video)?
What's the resolution of it's counting? (and it's display of that #?)

Some apps will count by samples, but display by msec, frames, fractions of whole sec., which may require some rounding in the display, making it not match how some other app, also counting by samples but displaying differently. Unfortunately, there are MANY variations on this. Usually, though, it's the same file with the same true internal length, so one shouldn't need to worry.

Now, if it's TRULY not extracting the WHOLE audio stream, that's a bad thing. If you're worried about this, have 2 different apps extract the same stream from the same file and do a Binary File compare to see how they're different, or load both in a multitrack-capable audio editor and line them up to visually see the difference in the waveforms.

Scott

[ZiGGY909]

Thanks for the info, its all quite complicated for me.

I can safely say "its good enough", but it's not perfect.

When I convert 25>25 I can see its perfect, but when doing 23>29 conversions, the sound does not see to be perfect.

Can anyone please suggest the best method on converting 23.976 to 29.97? Or will it always be juddery??

thanks for help

[Pinstripes23]

I have converted a 23.976 AVI into a 29.97 MPV, I use CCE with a 3:2 pulldown.

The mpv file should be encoded as 23.976 if you used pulldown, not 29.97fps. Run the mpv through g-spot to see you encoded as 23.976. As long as you encoded to the same framerate as the original source and the audio does not have some delay before you decompress to wav, it should stay in sync after muxing. Pulldown are just flags inserted into the encoded file. They are more for authoring progs and dvd players. But if you play the muxed file on your PC with something like MPC, it should just display the encoded progressive frames at the framerate of 23.976.

[ZiGGY909]

It is I think.

It just don't look good enough. All my 25>25 conversions are perfect, can actually see the audio is perfectly in sync... But when ever I convert 23>29, they always look like crap. Audio is in sync, but it looks strange and un-natural.

hope im making sense

[ZiGGY909]

please help

[manono]

Help what? In what way is it strange and unnatural? Do you mean the Aspect Ratio is off? Aren't you using an AviSynth script generated by FitCD to frameserve into CCE for the encoding? Got a sample you can upload that shows the problem? Or are you talking only about the audio? Or about the slightly jerky movement?

Can anyone please suggest the best method on converting 23.976 to 29.97? Or will it always be juddery??

Playback will always be "juddery" That's the nature of 3:2 pulldown. It doesn't usually bother NTSC people, because we're so used to it. PAL people, used to completely smooth playback, are sometimes bothered by it. This assumes you're doing it right. Are you bothered by commercial retail NTSC DVDs which also have 3:2 pulldown, or are you saying the ones you make are different somehow? Again, got a small sample showing the problem? 10 seconds of a section with movement will be enough.

[Pinstripes23]

It is I think.

It just don't look good enough. All my 25>25 conversions are perfect, can actually see the audio is perfectly in sync... But when ever I convert 23>29, they always look like crap. Audio is in sync, but it looks strange and un-natural.

hope im making sense

Yes provide a sample as suggested. Are you saying it seems different from the original source avi?

[ZiGGY909]

Hi guys

The video/aspect is fine. What I meant it don't look as good compared to all my pal>pal encodes. But I guess as manano said, this is the consequence of 3:2 pulldown.

Here's a sample vob... when they open theres mouths, the audio doesn't look natural... but it could be just me. Guess im being to fussy!

http://download.yousendit.com/5A08FBD70F2ED5D2

password: videohelp

[manono]

Looks good to me. In fact, you did a pretty good job on it. If pulldown bothers you, about all I can suggest is to encode it for PAL. Make it 720x576, add in AssumeFPS(25) to the script, encode for 25fps in CCE, and adjust the audio by speeding it up.

There's always a chance, I suppose, that whatever you're using to play it back is contributing to the problem. I only played the VOB using Media Player Classic. When you play the DVD on the TV, if your player or TV set doesn't do a good NTSC2PAL conversion, that might contribute to the problem.

[the * dude]

ha not a noob q ???

why don't you just encode it in its native frame rate and use dgpulldown to covert to to any frame rate.... :P

you eliminate any fear of miss sync.... less your source is to blame!!!!