Editing MPEG-2 Files / Jumpy Rendered Quality

Ginger wrote on 5/6/2003, 4:26 PM
Frustrated newbie here needing serious help! I have an MPEG-2 source file that I am trying to edit. I opened the file in V4, made my edits, saved and rendered it. I then used DVD-A to create my menus and burned the DVD using DVD-NTSC format). The final results were horrible. The video was severely jumpy throughout. After days and weeks, I finally ran a test and skipped the rendering process in V4 altogether. I pulled up the source file in DVD-A and burned it directly onto the DVD. The outcome was exactly as I'd hoped - no jumpy video.

Here's my problem: How do I edit the commercials out of my original MPEG-2 source file since this isn't possible in DVD-A, and not possible in V-4 without losing major quality (producing jumpy video)? I've come to the conclusion that the jumpy video is a result of the double rendering process from V4 to DVD-A, correct?

I'm using a new external Sony DRX-500ULX burner hooked up with firewire. BTW, the re-rendered output plays great in my Windows Media Player and other such programs. It's on all of my DVD players that it's jumpy. I have four different DVD players, all relatively new. I've determined it's not the DVD players since the file I burned from the MPEG-2 directly (without having rendered it in V4 first) played just fine.

Your help is greatly appreciated. I have a huge project ahead of me, with over 60 hours of editing - and have spent weeks trying to get just my first 45 minutes of video work done. Please let me know if there's any other I need to provide.

Comments

JohnnyRoy wrote on 5/6/2003, 11:16 PM
It sounds like it might be an interlace field order problem. If the original MPEG was rendered upper field first you re-render it lower field first (or visa versa) it will play OK on a computer screen (which is progressive scan) but will be jumpy on a TV, which is interlaced.

Check the interlace of the MPEG while on the timeline in Vegas by using the Properties dialog on the Media tab. It will say either lower field first, upper filed first, or progressive scan. Make sure when you re-render it, you go into the Options dialog and check that you are rendering it the same way it was originally.

I would have to say that MPEG2 is not best format for editing. You should really use DV source on future projects as you will always get noticeable quality loss in the re-render of the MPEG file. It shouldn’t be jumpy, but it will have additional compression artifacts that you wouldn’t get if you started with DV or even MJPEG source files.

~jr
RBartlett wrote on 5/7/2003, 2:39 AM
for straight cuts, TMPGEnc can do this by breaking the streams into new files instead of rendering. I think VirtualDub does this too.
Files need to be .mpg .mp2 or possibly .vob or .vro (unpack/demux as necessary)

Vegas has to recompress unless you use uncompressed or DV that go out in either of these same formats. Going out with MPEG-2, and thereby recompression makes it difficult to choose an appropriate bitrate/GOP irresepctive of what information you have about the source file.

When jumpy, is it fluid frame updates but jittery on motion? If so, then you might have a fielding issue, but 480 MPEG-2 is unusual to have this trouble. As you say it plays back ok on a PC player, that makes this more likely. Have you got a TV-out card that you could check the field dominance upon from mediaplayer through?

I thought DVDA was ok at doing in/out points from a single MPEG-2 source A/V set? I'd guess that would be without recompression and without putting more onto the DVD than is actually viewable.
Ginger wrote on 5/7/2003, 7:23 PM
I checked the field order as indicated in your message, but that still didn't work. The finished product remains jumpy...choppy like. I've checked and checked and can't figure out what to do. Unfortunately, the source files are all in MPEG-2 format which I can't control.

Any other suggestions?

Thanks.
JohnnyRoy wrote on 5/8/2003, 10:41 AM
It sounds like you’ve ruled out the field order problem. I guess it’s a problem with Vegas re-encoding the MPEG2 file. I wish I could be more help.

~jr
RBartlett wrote on 5/8/2003, 4:12 PM
It might be worth converting your source MPEG-2 into I-frames only.
Perhaps even uncompressed, MJPEG or DV first.

It is possible to frameserve MPEG using VFAPI from TMPGEnc, and possibly helped by Dvd2AVI. Vegas will receive uncompressed 4:2:2 without having to fit an additional instance of your sources on any drive.

Tolerance to an MPEG needs to consider such things as GOP, timecode/header validity and whether the stream is system, program, elementary or transport.

Give Vegas its best chance at fairly inspecting every frame.
I wouldn't blame Sony for removing MPEG-2 editing from Vegas but would rather they didn't have the same blinkers as Micro$oft.