Variable FRAMErate dvd demuxing

[gbi]

Hi, i'm trying to demux a dvd with VFR Just the standart routine - extract the movie only and leave it with only one audio stream to fit on dvd 5.

Usually for demuxing i use vobedit, PGCdemux or TMPGenc but this time it seems they can not handle variable fps .vob files
Right after the demuxing the duration of the m2v stream is shorter than the real one and of course when i mux it back together the audio is totally out of sync

(sorry for my bad english)

[guns1inger]

The DVD specification doesn't allow for variable framerates, so either you don't have variable frame rates, and something else is wrong, or you don't have a compliant DVD.

How are you ripping the DVD to your HDD in the first place ?

[jagabo]

The DVD specification doesn't allow for variable framerates

That's not exactly true. Each GOP can use a progressive frame rate between 20 an 29.97 fps and pulldown flags to specify the final 59.94 field per second output (nominally called 29.97 frames per second). So the progressive frame rate of successive GOP can vary, even though the final field output rate must always be 59.94 fields per second. Many tools don't handle varying pulldown patterns properly because they look only at the first GOP and assume the rest of the video is the same. In fact, some tools don't even handle straight 25 fps with 3:2:3:2:2 pulldown flag properly.

I often see the studio logo at the start of a VOB file with a different frame rate than the main movie. Or videos that switch randomly between 29.97 fps interlaced and 23.976 fps progressive with pulldown flags.

I'm not sure if something similar can happen with PAL DVDs.

[guns1inger]

Not something I have seen with PAL DVDs, but given the simplicity of the PAL format - a straight 25 fps for all material, no pulldown requirements etc. - it is not something I would expect to see.

I have certainly seen mixed 23.976/29.970 material on NTSC discs, but I cannot recall ever have seen it mixed in the one title, or framerates outside this range.

Edit :

If this is the case with the OP's problem then the issue is not one of demuxing, but of getting a converter that can read and and correctly interpret the variable pulldown settings in the stream. All demuxing can ever do it retrieve the video as it was encoded. It is up to whaever is doing the reading/encoding to work out the rest.

[manono]

I think the guy doesn't know what he's talking about, and agree with guns1inger. He said the length after demuxing isn't correct, where most people know a player doesn't give the correct length when playing an M2V. Out of synch audio could be for a number of reasons not having anything to do with VFR. There's very little chance of him having anything remotely resembling a VFR DVD (if PAL). At the worst, he's got an NTSC DVD which is a mixture of film and video.

He may never come back, but if he does I, for one, would like to see a small sample of a VFR DVD.

[gbi]

jagabo, at first i also thought it is something about switching 29.97 and 23.976 but this dvd is PAL :P
This is the dvd - http://www.amazon.com/Live-at-Montreux-2007-Naturally/dp/B0012IWNYK

I use ffdshow for computer playback and until now it reports always the correct fps but with this dvd the fps is varying between roughly 24,4 and 25,6

guns1inger, i used dvddecrypter for ripping

[manono]

You say it's PAL; the link says it's NTSC.

I use ffdshow for computer playback and until now it reports always the correct fps but with this dvd the fps is varying between roughly 24,4 and 25,6

Means nothing. If it really is PAL it's 25fps and only 25fps. Maybe some or even all has been converted to PAL from film and/or NTSC video, but it still plays back at 25fps.

[guns1inger]

ffdshow is just a codec - what player do you use ?

I know mpc never shows stable framerates when playing back DVDs on my system, even though I also know they are constant framerate videos, and they are playing correctly.

I would run the DVD structure through fixvts or try ripping with DVDFab HD Decrypter

[jagabo]

Yes. the video renderer filter can't show a stable frame rate because the display is typically running at 60 Hz. So some frames of 23.976 fps material are being displayed for 2 scans, some for 3. That is, some frames are being displayed for 1/30 second, some for 1/20 second. This causes the fps counter to bounce around.