Accurate file size prediction with 2-pass VBR? And other Q's

[scottrempel]

How do I get an accurate file size out of TMPGEnc? I am creating xVCD's. I use 2-pass VBR with min=0, max=2500-4000 and set the avg so that tmpg says the file will be 800MB. When everything is done I end up many times with a file size that is closer to 600MB. I want to beable to get as close to 800MB as possible but obviously tmpg does not predict the file size well.

Also, is the mpg I create with 2-pass VBR with file size 600MB better quality then a CBR encoding with same avg but file size of 800MB.

Another question! Sould I make the max bitrate as high as possible (i.e. 5000 for my standalone) or should I keep it closer to the avg. (e.g. if my avg is 2000 should I use a max of say 3000 or turn all the way up to 5000.)

Does setting the min to 0 effect the quality in any way. What I mean is would setting the min to something higher like 1000 increase the quality of low motion sceens or would this just be overkill?

Thank you for any help you can give!!!

[bugster]

The bitrate calculator that TmpGenc has as part of its wizard is not very accurate, use the java one in the VCDHELP tools section.

Also, is the mpg I create with 2-pass VBR with file size 600MB better quality then a CBR encoding with same avg but file size of 800MB.

Quality is very subjective, you decide.

Another question! Sould I make the max bitrate as high as possible (i.e. 5000 for my standalone) or should I keep it closer to the avg. (e.g. if my avg is 2000 should I use a max of say 3000 or turn all the way up to 5000.)

My Opinion on this: If you set the Max bitrate high AND the movie has lots of high motion scenes, the high motion scenes will look better than they otherwise would, but the low motion scenes will suffer. If you lower tha MAX to a bit closer to the average, the 'average' quality would improve but high motion scenes will suffer. Again, see my previous answer.

Does setting the min to 0 effect the quality in any way. What I mean is would setting the min to something higher like 1000 increase the quality of low motion sceens or would this just be overkill?

I would suggest leaving the min at the value in the original SVCD templates. Some Players have problems with very low bitrates. Increasing the min above what is set in those templates would simply waste bitrate where not required.


Basically you MIN-AVG-MAX settings are a compromise and can be adjusted to suit personal tastes and type of movie. The only surefire way of getting the best settings is to experiment and decide for yourself what you prefer.

Hope this helps

Bugster

[scottrempel]

Thank you for responding to my question bugster.