Why do my xvid conversions have huge filesizes?

[Otto]

I've got an mpeg2 encoder card, and I'm trying to convert some of my recorded tv shows (regular 4:3 format) to xvid. The resolution of the captures is 720X576, and I was using AutoGK to convert to xvid. For the audio I was using Lame 128K mp3.

All my conversions are ending up close to 500 megs, even though the shows are only 20 minutes long after the commercials are edited out! I'm guessing the files should only be about 175 megs (from other conversions I have seen online).

What could I be doing wrong? I thought I might need to resize, but I didn't see any options to do that. Do I need to use other software with more advanced options (like virtual dub)?

Any help is appreciated. Thanks!

[Baldrick]

Did you set the output size to 175 MB in autogk? Resizing doesn't affect how big the file will be only the video and audio bitrate.

[Otto]

Did you set the output size to 175 MB in autogk? Resizing doesn't affect how big the file will be only the video and audio bitrate.

I did that and it worked, but I don't understand how resolution doesn't have anything to do with filesize. Since my captures are 720X576, I figured resizing to something like 640X480 would allow me to use a higher bitrate for my target filesize. It doesn't work this way?

[celtic_druid]

Size = bitrate*time. The resolution would effect the bitrate if you were encoding at a fixed quant though.
640x480 at Q2 should be smaller than 720x576 at Q2.