Bitrate settings
by Johan Lundqvist
on
Oct 1, 2008 at 10:02:44 am
Default settings in Vegas for mainconcept mpeg-2 with a DVD template has these settings: Variable bitrate (max 9 500 000, average 6 000 000, minimum 192 000).
If disc-space is not an issue, would you recommend using these settings? I've seen discussions on the internet suggesting that vbr with a maximum of 9 500 000 is like asking for trouble. Would it be just as good - and safer - to use a setting of max 8 500 000, or even 8 000 000? Is 6 000 000 good as an average? And does not min 192 000 seem very low?
And if disc-space is not an issue, wouldn't it be better to use cbr?
Re: Bitrate settings by John Rofrano on Oct 1, 2008 at 11:38:01 am
The key number with VBR is the Average bitrate. This says that on average, use 6MBps. It doesn't matter how low the Low is because if it can't represent the frame with that little amount of bits it won't. Telling it not to go above 9.5Mbps is within the DVD spec and I would only expect that to happen for a brief moment if the overall video is to maintain a 6Mbps average.
It's a balancing act for the encoder. That's why 2-Pass gives better results. It lets the encoder go through the video and determine where it needs the bits, then it optimizes a plan for using the available bits most effectively, and then it encodes using the plan. You might want to try using 2-pass encoding and see if your video looks better but it takes twice as long (as the name implies).
CBR is great when disc space is not an issue because each frame gets the same amount of bits whether it needs them or not but I wouldn't set the CBR above 8.5Mbps because some older DVD players have trouble with really high bitrates. They should work but some don't. Why tempt fate?
