How to recompress video clips for internet transfer or CD burning

When transferring video clips over the internet it's important to limit file length. This goes for cd burning as well, the limit being 700 MB. VirtualDub is a great tool for cutting clips down to size.

Let's take an example. A 55 minute clip (size: 2,25 GB) originally recorded with the ATI All in Wonder Radeon card using the Morgan Multimedia MJPEG V3 video codec and the CCITT A-law audio codec can be boiled down to 500 MB without serious loss of picture quality and no sound quality loss at all. Here's the recipe:

1) In VirtualDub's Video menu, select Full processing mode and choose compression:

2) Select the Microsoft MPEG-4 Video Codec V2 with these settings, keyframe=1 being the crucial change:

3) Select Audio/Full processing mode

4) Select Audio/Conversion with these settings:

Select File/save as avi, give the file a name and let VirtualDub do the rest.

The result is a file with a reasonable download size that can be used by the receiver without further processing for scene change detection.

You may bring down the size even more (to less than 3 MB per minute) by recompressing sound with the MPEG layer 3 (mp3) codec:

1) Select Audio/Full processing mode

2) Select MPEG Layer-3 with these settings:

3) As MP3 compression may give sync problems, use audio skew correction if necessary. Select Audio/Interleaving:

A value of -300 ms normally yields good sync results when converting Dazzle MPEG files to MPEG-4/MP3 files, else experiment! Even if you make/receive a out-of-sync conversion you can always reconvert it with new audio delay values without any loss of video or audio quality.

If you're having problems viewing the MPEG-4 video clip, a quick solution is to install the freeware codec handler FFDshow from http://sourceforge.net/project/showfiles.php?group_id=53761