AVI to FLV: achieving the best file size?

[Pixelrage]

I'm a total newbie with all of this conversion stuff, so bear with me I tried a bunch of different ways to get the smallest FLV file size possible. In the end, they all wound up at the same filesize, and I don't really understand it.

Trial 1:
-Virtualdub->AVI file, 30 seconds long, 400x300 (200 megs or so)
-saved as a regular AVI to the desktop
-opened in Riva and saved as an FLV with bitrate in the 700 area, 400x300, 30 FPS
-filesize = about 6 MB (not what I was looking for).

Trial 2:
-Virtualdub->AVI file, 30 seconds long, 400x300 (200 megs or so)
-saved as a regular AVI with DIVX compression to the desktop
-opened in Riva and saved as an FLV with bitrate in the 700 area, 400x300, 30 FPS
-filesize = about 6 MB (same exact size as trial 1-- why??)

Trial 3:
-Virtualdub->AVI file, 30 seconds long, 400x300 (200 megs or so)
-saved as a regular AVI to the desktop
-opened directly in Divx (paid version) and compressed to a new AVI
-opened in Riva and saved as an FLV with bitrate in the 700 area, 400x300, 30 FPS
-filesize = about 6 MB (same exact size as trial 1 and 2-- once again, why??)

I don't understand why a regular AVI and a DIVX'ed AVI would both yield the same exact FLV file when converted. Is there any way to get a better deal than a 5 MB FLV file in the end?

Thanks!

[Baldrick]

The source avi file size and resolution doesn't matter. It's only the video, audio bitrate and play time that is important for the file size. Use a bitrate calculator to calculate the output size (see tools list to the left in the menu), You should be able to use almost 1400kbits for a 30 sec clip without audio....if you use 700kbits it should be 2.5MB...

[Scorpion King]

I just did a 30 second FLV using 900Kbps cbr and 160Kbps mp3 and the file was only 3.9MB.

[Pixelrage]

That's a little better than the size I get. Isn't there any way to get that file size below or about 1 MB?

[Scorpion King]

1MB filesize
30sec video
128Kbps mp3 audio
142Kbps video bitrate = not very good quality
lol

good luck

[jagabo]

file size = bitrate * running time

Bitrate is the combined bitrate for both audio and video. If you want smaller files use lower bitrates. In your trials you asked for the same bitrate all three times. The encoder delivered it -- hence the files are the same size.

There are exceptions to this at the extremes where an encoder can't get the bitrate high or low enough to meet the requested rate.

If the video is too badly mangled by a low bitrate you can try using a smaller frames size. The smaller the frame the less bitrate it needs to retain image qulaity. You can also try reducing the frame rate. Fewer frames per second requires lee bitrate. If your source video is noisy (snow or grain) noise filtering may help (noise makes video less compressible).