Get the feeling AC3 audio and TMPGEnc MPEG2 don't mix

[Bullworth]

I beginning to think the reason that TMPGEnc video and IFOEdit have problems is with the AC3 audio. I've already conducted several test encoding a single VOB demuxed according to Doom9's and Derrow's guides and while the m2v file plays smoothly as soon as I remux in the AC3 audio it is completely out of whack. The audio plays fine the but the video plays in a jerky fashion that leaves is further and further out of synch. I've re-encoded the audio into mp2 and wav and remuxed it and it plays smoothly. Might be on to somthing. probably not. Thinking there has to be a way to demux the audio and then remux it back into the vob somehow. By the way, what audio formats are acceptable for DVD? I know Ac3 is most desirable due to surround sound but I'm willing to part with it until some better method comes along If it means it will solve the problem for keeping the original menus.

[tonyp12]

Just to make sure (NTSC):

Must use "force film" in DVD2AVI

TMGENC use 23 (29 internally) and encode mode: 2:3 pulldown


You are using this guide?
http://www.doom9.org/mpg/tmpg-dvdencoding.htm

[Bullworth]

I've double checked the settings and saved them as a template to make sure everything stays as it should be. Do you mean 3:2 pulldown as mentoined in the guide? I've encoded the VOB about 4 times to see what the results will be: one using Doom9's specs, one changing the VBV to 224, the original setting; one with the 3:2 pull down filter activated and another without. Gonna see if any of these help. What is the diffence between the Encode mode 3:2 pulldown and the one in the filters tab? Sure hope it works this time. ReMPEG is OK for drama but is bad for action sequences ( read Scorpion King, The Fast and the Furious)

[tonyp12]

VBV should be set to: 0

3:2 pulldown.

This is how NTSC DVDs works:

They are encoded at 23.976 frames/second.
(the same framerate as in the movie theather)

During Playback your DVD player adds an extra frame every 4th frame.
And uses the TV interlace feature to mix that in to two frames, so you
can not really notice it.


When you copy a DVD you should do that at 23.976 with encode mode
3:2 (just a flag) as that how the original DVD is done.



I just found some more info here, but I think I got it right.
http://www.doom9.org/synch.htm

[BJ_M]

not all dvd's are 23.97 .. check first always if 23.97 progressive or 29.97 interlaced ..

TMPGEnc has a little bug if you set VBV (buffer level) to 0 .. it should be set to 224 for dvd's .. if you dont it varies right at the start and causes buffer over/underflows ussually right at the first few frames -- at least we see this on all tmpgenc versions up to 2.53 , havnt checked more recent versions ..


What is 3:2 Pulldown?
"Film" is shot at 24 frames per second (fps), but NTSC television signals run at 30 fps. As a result, it is necessary to convert the 24 distinct frames in a second of film into 30 new frames that can be played back on television; if you were to ignore this different frame rate and attempt to play back your film material at a 1:1 ratio with video frames, your material would play back at 125% of the actual speed -- a one minute film clip would playback in 48 seconds! Please note that only NTSC video contains this 3:2 pattern, as PAL video runs at 25 fps and contains an altogether different pattern to solve the problem (24:1 pulldown).

During "telecine" (aka film-to-tape transfer) when film material is transferred to video, a 3:2 pulldown sequence is introduced into the footage which mixes alternating combinations of 3 and 2 video fields. This sequence essentially stretches the 24 frames in a second of film into 30 frames, so that when they are played back as video they transpire in the same 1 second that they would have on film.

Why does 3:2 pulldown work? Because there are 2 fields per frame of NTSC (see the fields white paper for more info on fields and NTSC) which adds up to 60 fields in a second. For those of you who like math: 24 and 60 have a common denominator of 12; 2*12=24, and 3*12=36. Thus, by mixing 2 and 3 patterns of fields (24+36), we get to 60 fields in a second!

Let's consider how these frames of film get mapped into fields of video. If the first frame of film is taken and placed on 2 fields of video, then the next frame is taken and placed on 3 fields, then 2, then 3 (and so on)... the result is that every 4 frames of film will land on every five frames of video (24/6=4 frames at film rate, 30/6=5 frames of video at rate).



This pattern of video frames is what is called 3:2 Pulldown. It is a repeating sequence with five (5) variations, although by looking at the various language and methods used by software/hardware tools that insert and remove this pattern, you would think there were 100 flavors of 3:2 Pulldown! What Avid's Film Composer calls an "A Frame" on video, is what Accom DDRs call "Phase 3", and Adobe After Effects calls "WWSSW".

the bottom field is called field 1 and top field is called field 2 ..

[Bullworth]

Wow! That's a sh!tload of info, way more than I expected but I personally like it that way. At least I get a good understanding as to what it going on rather than simply trying to figure it out. Thanks tony & BJ.

[tonyp12]

I just did my first transcode, the moive do have some jerky movement
and the audio is out of sync right from the start and get worse torwards
the end.

The IFOEDIT guides says that tmpgenc does have the sync problem.
But how do you get rid of them?

I will try to rencode with a VBV: 224.

I use TMPGENC 2.58 so I do not know if that bug is still there.

[BJ_M]

yes but buffer underruns will not cause your audio to go THAT out of sync ..

there would be another problem .. tmpgenc doesnt have a problem with sync - it is that the source and/or settings cause it to go out ..

[Bullworth]

Just finished re-encoding a movie VOB and the same thing keeps happening. m2v plays fine but is jerky and out of synch when I remux it. I hate to say it but this DVD stuff is really starting to get on my last f***ing nerve. I've tried encoding using both Force Film and None, using 0 VBV and 224, using Force Picture Type and not using it and nothing is working. I've double checked all the settings and it always ends up the same no what. Hey BJ-M, what settings to you use and how do you go about transcoding. I've followed the Doom9 guide but something isn't right since it goes out of what every time.

[Bullworth]

I just finished encoding a batch of VOBs, one of them I did a regular 29.97 d2v and the other was force film. I encoded the 29.97 on using 0 and 224 for the VBV buffer and with and without the Force Setting checked. Did the same with the Force Film d2v. Gonna see what the results are and will post in a few hours. Read on Doom9's site that there are times when it is not necessary to encode at 29.97/. This link explains it.

[tonyp12]

Do anyone know if you still have to do what's quoted below for v0.932?

How to use:
Load the IFO file of your main-movie, and press the button 'Create Tmpg T.'.
In the filedialog, specify where you want to have the Template.txt file written to.
Now IfoEdit starts to scan the first VOB file. You must press now the 'CANCEL' button in the progress dialog (after 1% or 2% completion).
IfoEdit displayes you now the GOP structures, that have been found in the VOB file. You need to select one of them, which will be assumed to be the STANDARD GOP STRUCTURE.
When you have selected one, and clicked 'OK', then IfoEdit will start creating the Template.txt file.
It writes all I frames to the template-file, and when ever it finds a GOP structure, different then the one you specified as STANDARD, then IfoEdit will write all frames of that structure into the template file.

[tonyp12]

I will try to rencode with a VBV: 224.

I use TMPGENC 2.58 so I do not know if that bug is still there.

I gave up using tmpgenc and moved to ReMpeg.

The sound is in sync but the movie freeze a few frames every second.
(both on PowerDVD and standalone DVD player)

So the Verdict:
The re-mux part of IFOedit needs work.

If a movie is bigger than 4.3GB even after
being stripped I will not go on transcoding.

[Bullworth]

Read in a post elsewhere that since version 0.62 there has been a problem with the re-mux portion. Use 0.62 for remuxing and the latest for anything else. I transcoded a single VOB remuxed and it played fine.

[dazsafc]

When you said Pal is 24:1 rather than 3:2 pull down is that the telecine option 30fps to 24 on TMPGenc. Would that be converting from 23.9 to 25 or 29.7 . Or does TMPgwnc not have that 24:1 option.