constant OR variable mpeg2 encoding ?!

[lenti_75]

what is the best way, regarding the quality, to convert into mpeg2 files....using the Constant Bit Rate or Variable Bit Rate ?
I converted using both, and I haven't noticed any difference, except the size.
Is there any difference when you want to keep the best quality ?

[SLK001]

Given the choice between these two options:

CBR @ 9Mbps, or
2 pass VBR @ Min=9Mbps, Avg=9Mbps, Max=9Mbps,

and assuming the identical GOP structure (they will be basically the same size when done), the 2 pass VBR will give slightly better results, because your encoder will find the scene changes and close the previous GOP and put an "I" frame at the beginning of the scene change. This is at the cost of twice as long to encode as the CBR.

[Vejita-sama]

The best quaility comes from encoding at the max supported DVD bitrate. But this is normally overkill and doens't allow for much runtime per disc.

MPEG file sizes are controlled by runtime and bitrate
MPEG video quality is controlled but resolution and bitrate

So the higher the bitrate the better the quaility, but the larger the file size, which in turn means shorter runtimes. What often happens is that people want to put say 2hrs on a DVDR disc. So they calculate what bitrate will generate a 4.3GB DVD (including audio, subs, etc) and encode at that bitrate.

Now we get into personal opinion. If you encode at anything less than the DVD max of 9800kbit/s you're reducing quaility, but no one can see the difference between 9800kbit/s and 9799kbit/s Personally unless the bitrate drops below 6000~6500kbit/s I just use CBR as it's faster. Below that I use 2 pass VBR, and for really low bitrates 3-4pass VBR. But these are personal choices.