Editing Mpeg 2 files and re-compression

PDB wrote on 4/13/2004, 3:45 AM

Hi all,

Just a quick question (or three...) regarding working with mpeg 2 files in Vegas. What exactly are the caveats with editing these files? What quality can one expect if one edits a mpeg 2 file and the compresses it back to mpeg 2? Does the compression work like in DV? (ie. only the edited frames -transitions, effects etc - will be recompressed while the untouched frames will be "copied"?

Thanks for any light on this!

all the best,

Paul.

Comments

Chienworks wrote on 4/13/2004, 4:11 AM

Vegas is not optimized for MPEG sources. The caveat is "don't do it."

If your source file is very high bitrate and is all I-frames then you might get some usable results with moderately useful speed. You're not likely to come accross much of this sort of source material though unless you create it that way yourself. And, if you're going to go through that much trouble to create such files, you might as well use DV instead.

If your source file is a medium or low bitrate then you can expect rapidly increasing amounts of artifacts with each re-render. Vegas will always decompress and recompress every frame of MPEG even if no changes are being made.

If your file contains anything other than I-frames then expect long delays as you scroll through the timeline while Vegas reconstructs the frames in order to display them. It can get bad enough that you might feel like your computer is locking up and crashing.

If your source material is only available in MPEG format then you should probably consider converting it to DV .avi files first before trying to edit. This won't save you from any of the quality problems, but it will speed up the editing process enormously.

retrofilms wrote on 4/13/2004, 6:55 AM

If you really want effortless and frame-accurate editing of MPEG2 files check out MPEG-VCR found here:

www.womble.com

I use it all the time for cutting the commercials from MPEGs created with my ReplayTV. If all you do is edit, there is no recompression when saving, which makes the process really fast! It also includes other useful tools and the interface is wonderful.

When I bought this program a few years back, it was more than worth the $250 I paid for it. Now it sells for a ridiculously low $70!!! It is an excellent value if you need to cut up or splice together MPEGs. On top of all that, it is try-before-you-buy, which eliminates any excuse to ignore it. Vegas is great, but this program rules the MPEG editing world.

PDB wrote on 4/13/2004, 11:04 AM

N/t