poll on video bitrates for divx encodes

[mistik69]

Im curious to what a good "rule of thumb" is for video bitrate encodes. Im looking for the optimal file size vs. quality bitrate for an average dvd to divx or xvid encode. I usually use around 1000kbps.

[CWR03]

There are too many variables involved in determining a bitrate. Amount of motion in the file, lots of darkness, an animated show or movie, even the resolution all play factors in quality vs. bitrate. Bottom line: do a few tests and see what looks best to you.

[Awatef]

Well, what CWR says is true but when you don't have the time to do a compressibility test (or are not sure about which portion of the movie to use to be representative), you would want to follow the "at least 0.15 bit/pixel" rule.
Like if you have 720x304@24fps, you shouldn't go below 790kbps, where it is not recommended to go below 1110kbps for 640x480@24fps.
A trade-off would be to do a 1-pass quality based encoding on the whole movie with quantizer 2 while enabling logging. Then proceed directly to the 2nd pass, putting a bitrate that would produce at least 33% of the size of the quality based encode.
If the size you want to achieve corresponds to less than the third, you should reduce the resolution proportionally.
Example:
I want to fit a movie on 700MB. The quality based encode produces a 2500MB file at 720x304. Here the third is bigger than 700 (833MB). I then reduce the resolution down to something below 179334 pixels (720x304x700/833), for example 640x272, and do the 2nd pass with that.

[weaver4]

What CRW03 said is true, it is very difficult to know. You could always encode the whole movie watch it and see if it looked ok or.....you could do what I do.....set the coder to single pass then set the quantizer and let the coder figure out how to make it it good quality. I have had the best results doing this. Here are my guidlines for quantizer settings.

Quantizer 4 - Good Results
Quantizer 3.5 - Very Good Results
Quantizer 3 - Excellent (really too good for the filespace it uses)

So most every movie I do in Quantizer 4 except my favorites which I do in 3.5.

Give it a shot.