[Mediaman_12]

I have a load of .MPG files that I need to reduce in size (both dimension's and file size). I can open and play them in QT no problem, but if I edit them (using the movie properties to reduce the size) and save or export them it strips the Audio.
I foolishly brought them home from work, I thought it would be no problem, and nice an fast on my Twin G4.
Oh the properties says it is a MPEG1 Muxed track (I know, from my dealings with VCD's that it means that the Audio and Video share the same track).
Any Idea what I can do this with? An app I can download would be best.

[Nap]

You have to go outside of QT to solve the problem, as this article notes that QT does not support mpeg sound export:
http://docs.info.apple.com/article.html?artnum=61608
You can look for a rather new program for OS X (that I have heard of but not tried) called Export to QT. Look on VersionTracker to find it.
The other alternative is to demultiplex the mpegs with a program like BBDemux, then trick iTunes to convert the sound track to a non-mpeg format by changing the extension to .mp3 instead of m1a. The reason you have to do that is that QT will not let you export a demuxed audio stream so you have to convert it to a wave or AIFF file, for example.
Export the mpeg to a non-mpeg format video track(like component video or NONE, copy that track to the clipboard, then use Add Scaled to add the track to the non-mpeg audio track. You will then have a video/audio clip that QT will let you edit. If you do not change both demuxed tracks to a non-mpeg format QT definitely will not let you edit them.

[Uncle Skeleton]

I recommend you use ffmpeg. It can read and write mpeg just fine so you won't have to bother with any intermediate files

[Mediaman_12]

Used the export to QT app to get them in to QT .Mov files, then used QT pro to turn them in to MP4's (yay! loads smaller 30+MB to around 6MB). Does anyone know if a standard install of WMP9 on XP will play these?

[Uncle Skeleton]

they won't. but if they install 3ivx they will

[Mediaman_12]

Awww crud! these are for downloading from a commercial website. So having to install 3ivx to play them isn't really an option. But I couldn't work any of the other options to give a good reduction in file size, without the quality going to crap.
Any suggestions, the originals are 320x240 pixels and are just under 4 mins long, thay come in at around 35Mb (for the original mpg, the QT .mov files are 76MB!!!) and the .mp4's are 220x165 and come in at a nicer 7Mb.

[Uncle Skeleton]

mpeg1 is the most compatible, and the only video format that you can rely on people being able to play without any additional installation. Next most compatible is mov/mp4, since QuickTime is cross-platform and has a reasonably wide installed base. After that comes asf/wmv, rm and divx "avi," which are all technically available for most platforms, but have serious limitations and obstacles for mac users.

You always have to make trade-offs between the latest compression technology and how much of your audience you can expect to already have the capability to use that latest technology. Since you're apparently scaling down anyway, try scaling down to mpeg1 and see if that's small enough for you. Also you can set a lower bitrate (at the cost of quality) if you encode with an encoder like ffmpeg's (as opposed to Toast's which gives you no control).