AVI to AVI rendering: why does bitrate and file size change?

[dwiesel]

In searching this site, I haven't found mention of this particular issue...if there is one, I will gladly redirect my message there.

I'm trying to understand the rules of rendering one AVI to another AVI. To keep it even simpler, assume the new AVI is in the same colorspace (RGB to RGB, YUV to YUV)

In my example, my file is captured in YUY2 and --without any changes-- I'm rendering it as a new YUY2 file (Obviously I could just copy it in Windows, but this example is to understand AVI rendering rules).

So in the above example I would expect the new file size to be identical to the original. However, the new file is smaller than the original. And, the bitrate has increased.

original file:
size = 1,505,450 KB
bitrate= 114609

new file:
size= 1,504,368 KB
bitrate= 114618

My questions:

1) why did the file size change?
2) why did the bitrate change?
3) are the size/bitrate changes proportional?
4) is the new file the same quality?
5) what is the overall effect of the change, if any?
5) how will this affect my final MPG quality?

Thanks all.

[dwiesel]

Hmmm...nothing yet from the gallery...must be a tough one...or, folks are just sick of this stuff.