Comments

riredale wrote on 9/26/2002, 2:31 AM
I am definitely NOT a Guru, but since DV is a pretty transparent format, I would not expect much degredation. On the other hand, DV and MPEG2 are different enough (colorspace is one example) that there might be some unhealthy interaction. Perhaps someone else here has done just what you propose.
jeffy82 wrote on 9/26/2002, 7:17 AM
I'm no guru either, I am basing this on my own experience.

Hurdle #1. Is the DVD Macrovision copyprotected. If so, I cannot help you. Your camcorder will stop as soon as you start recording. If it isn't copyprotected, (ie. if you or someone else burned it) you won't have a problem.

Methods:
1. Basically there are two ways. The way you suggest-- Connect the DVD player to your DV camcorder. But there is a higher degradation with this method, since its having to go from MPEG2---> Analog (S-video)---> DV (for editing)--->MPEG2 (reencoding). However this method assisted by the TBC in the Camcorder, can sometimes smooth out some of the issues experienced when performing a more direct digital transfer.

2. Depending on the amount and type of "Slight Edits" you are referring, you may be able to retain the MPEG2 quality without any loss in degradation, however, its by no means the easy way. Oversimplified, it's like editing a book by changing the table of contents.

3.Of course there are many ways in between. There are tradeoffs with each. You can look at some guides at doom9.org
or vcdhelp.com

Welcome to the world of Digital Editing.
Jeffy82@aol.com
Widetrack wrote on 9/26/2002, 6:57 PM
Jefferey:

Thanks for the reply. I'm actually not taking it back to MPEG, but VHS, so the re-encoding will not be a problem.

But I keep re-reading your post and I'm not seeing the second method you mentioned. Can you clarify?

Thanks
mikkie wrote on 9/27/2002, 12:09 PM
If I've got it right, you're going from DVD to VHS. The best way, without going through much if any degradation, is to take the mpeg2 on the DVD and record it. Sad to say, the folks that came up with the DVD spec thought of this long ago, and threw in a bunch of hurtles, both legal and through technology. Staying away from all legal aspects and issues....

The DVD video stream is pretty pristine (assuming the DVD was done well), but most all stand alone players are limited to something like VHS quality on playback, if your VHS deck will even record them since they play with the signal through macrovision to trigger your VHS not to record or record in B&W etc...

The DVD drives for PCs are a different animal though, and there's a ton of software out there to transfer the files to your hard drive and unprotect them at the same time. Simply playing these back while outputting to tape is the easiest method, though the quality you get on tape is dependant on your video out hardware. It might not look as good on tape because you're often playing back a 24 fps progressive picture to a 29.97 interlaced format, and again, some hardware handles this better then others.

If you try to simply record the DVD playback from the DVD disc, Macrovision again causes problems, though in some cases there are software mods out there to make this work, and if you check out the video lan project, you might be satisfied with their client software.

In any case, there doesn't seem to be any benefit to actually record the video stream to your hard drive rather then transferring the mpeg2 files intact. And if you're not doing any editing & just going right back out, there seems to be little reason to bother converting the files to anything -- just play them back as they are.

If you are doing editing or have another reason for converting the files, the process gets much more involved as you not only have to deal with the mpeg 2 encoded as vob files, but separate audio streams too. Places like digital-digest have tons of info on that stuff -- far, far more then there's room for here.

As short as possible, you could convert all the vob files to avi (I would use something like picvideo instead of DV), and the way I'd do that is to use dvd2avi, then vfapi, & graphedit for the audio. This would give you a sort of virtual file that you could open in VV3 & edit, but you'd still be working with the original mpeg2 video files until you did the final render.

If you have ntfs discs, you could render one large file and play it back while recording to tape. If you use fat32, you might want to use virtual dub to create segmented avi files first, edit those files you have to, saving just those segments you edit in VV3 (keeping the segmented avi's in other words), & playing back in your choice of software -- you have to watch out for gaps between segments on playback, and might wind up using something like avi-io's playback options.

To change the existing vob files off the dvd with really the minimum if any recompression, I *Think* you would look at something like graphedit to extract more or less pure mpeg2 files, use freeware to cut out the parts you wanted to edit without recompressing these mpeg2 files, do your edits, saving them as separate mpg2 files to the same DVD specs, then put together another DVD structure with DVD software. In my opinion, you wouldn't notice the quality difference going to VHS, so I'ld stick with the option above, rendering to avi from VV3.

Hope that helps
John_Cline wrote on 9/27/2002, 12:17 PM
DVDs are not 24 frame progressive. While the film was originally 24P, it was converted to 29.97 interlaced using 3:2 pulldown for the DVD. Some DVD players will convert it back to 24P, but you would have to have a player that specifically does this and a television that accepts the signal.

John
mikkie wrote on 9/27/2002, 1:31 PM
Oops

Apologies first to the nice folks trying to read this thread looking for answers and stuff -- what this bickering contributes I have no idea, unless some folks enjoy baiting. Not a big deal really, but upsetting perhaps when it presents disinformation solely for that purpose....

Sorry John, but the way I understand it, DVD can incorporate 24 fps, 25 fps PAL, or 29.97 NTSC. Films converted for TV viewing go through a telicine process etc. to convert them to 29.97 -- the pull down you refer to.

It makes little sense with an internationally released DVD to encode all these different formats, fps, etc., so they most often retain their basic 24 fps with the player hard or soft ware handling the conversion on the fly while playing. As I said, most often... Every DVD I've seen has the film at 24 fps, with maybe a US market intro done NTSC and so on. The easiest way to tell that I'm aware of is run the VOB files off your hard drive through DVD2AVI -- chose the preview option and it will tell you what you've got in the specs window.

At any rate, let the readers check it out -- go to digital-digest.com or any host of dvd spec related sites, or check out any dvd on a hard drive with DVD2AVI.

As far as the other stuff, about dvd players converting fps, got it backwards 1, and 2, what would be the purpose of having a DVD player perform IVT (reversing the telecine process) if the DVD were encoded at 29.97 fps? IVT is a difficult, troubleprone process. TV's are interlaced devices, in the US running at 60 fields per second -- a 24 fps picture would look bad, and if progressive screen, really bad.

Computer monitors are progressive though, and display either interlaced or progressive video, whatever fps you choose. Deinterlacing is built in with some TV cards &/or their drivers, and the picture looks better -- else why would they include it. So, John, tell me the name of the software that displays a progressive, 24 fps picture when fed an NTSC video stream and I'm all ears.