MPEG-2 Bitrates are lying to me!!

[Sci]

I have been trying to encode a 50min television show onto CD by using MJPEG capture at 352x576 and encode them using TMPEGenc. I have set it as "2 pass variable Bitrate" with average bitrate 1364, min bitrate 300 and max bitrate at 1500kbps. THe audio is set at 192kbps in Layer II. I want to eventually have this on mini-DVD using some trial software on the internet (Works, 1 title, no menus).

I have three segments done so far.
The first was just over 8 minutes long so ended up ~90mb which would be correct to my calculations.

The second was about 12 minutes long but this file ended up being about 272mb where it should have only been just over 100.

Also the last segment was 14 minutes and this file ended up being 364mb.

So how come the first one worked but the second two are so high?

Cheers

Sci

(The clips are very low motion and recorded from VCR so the bitrates don't have to be too high)

[Walrus]

Make sure you set the motion estimation to normal. A bug in TMPEGenc is that the 2 pass VBR only correctly calculates the values with a normal settng.

[Sci]

Is that going to result in a lot of blockiness?

Thanks for the reply

Sci

[Walrus]

Sci: I can't say for sure. It depends on a lot of factors, but I'd say the odds are increased with using normal motion estimation versus one of the higher settings. Do note, I don't think the other VBR models are effected by this problem, so something like Constnat Quality may be a way around this. Encode once with this, and then adjust the quality setting to help get to your target bitrate and then encode again. This is sort of like a manual 2-pass vbr.