Accurate Bitrate in TMPEG?

[LanceSteel]

I'm trying to convert an avi to a DVD standard 352x480 MPEG2 stream. I've calcualted what the average bitrate should be in order for me to fit it on a single layer dvd. I'm using the CQ_VBR setting with a low value of 0 and a high value of 5000 and I set the average bitrate to be 62% (or 3100bps.) When I do this TMPEG uses a bitrate that is MUCH higher than what I specify which leaves me with a stream that is much larger than what I want. Am I doing something wrong or is TMPEG just having a hard time encoding the stream at that bitrate? If I set the percentage lower and lower, I end up with the ave bitrate that I desire but it is trial and error.

Also is CBR a valid option for DVD encoding?

Thanks.

[adam]

CQ_VBR is still only 1-pass vbr. Avg bitrates can only be specified when using multipass vbr. Regardless of what you calculate your avg should be it will never be anything more than trial and error with 1-pass vbr. If you want to set an avg bitrate and have the encoder respect it, you have to use multipass vbr.

Is cbr a valid option for dvd? Well if compression isn't an issue for your particular source than yes. If you only have 30 mins of so-so quality video to fit on a dvd then there is no point in using vbr. Or if encoding time is a major factor for you than using cbr will make the file encode much faster.

Hell I have even seen some commercial dvds encoded in cbr, though only in the bargain bins.

All in all, cbr is a very ineffiicient method of encoding. It should only be used in instances where its shortcomings are irrelavent.