Edited Video - Rendered File Size

[FunkHammer]

I am using Vegas Video 6 to do some basic editing of AVI/MPG files. The original files vary in size, usually between 400 - 500 MB. All I intend is to use Vegas to do some simple clipping/cutting in order to move around some of the video content, and perhaps add a quick title or two.

For example, a pre-edited file has the following specs:

TYPE: AVI (XviD)
VIDEO: 640x360, 29.970 fps, 552 MB
AUDIO: 192 kps 44, 100 Hz Stereo MPEG

After editing it (removing and rearranging some content) in Vegas and rendering it with the following specs...

TYPE: MPEG-2
VIDEO: 720x480, 29.97 fps
AUDIO: 224 kps, 44, 100 Hz, Layer 2

...the resulting output file is almost TWICE as large (over 800 MB) as the original. Is this because of the increased frame size and audio rate? How can I keep the rendered output file to a size closer to the orginal file? They need to each fit on a single disc for archiving.

Thanks.

[jagabo]

file size = bitrate * running time

"bitrate" is the sum of audio and video bitrates.

MPEG2 requires higher bitrates than MPEG4 (Xvid) to maintain image quality (2x to 4x usually).

Larger frame sizes require more bitrate to maintain quality.

Higher frame rates require more bitrate.

Higher audio sampling frequencies require more bitrate.

Use a bitrate calculator to determine the bitrates to fit the running time of your video on a DVD.

[guns1inger]

For mpeg2 material you are better off using a dedicated mpeg2 editor such as videoredo or womble. This will only re-encode the minimum required to perform your edits, whereas Vegas must uncompress and re-encode the entire video. If you use similar bitrates to the original to match the size you risk introducing artifacts.

For AVI files, consider virtualdub in Direct Stream Copy mode, if you can live with I-frame cuts only.

[FunkHammer]

I think I've got it figured out now. Thanks for all the feedback information -- it's been very helpful.