TMPGEnc Xpress bitrate calculations are off

[Taeran]

Greetings,

I have been doing some conversions from AVI to M2V using TMPGEnc Xpress 4.0, which now has a bitrate calculator. I used to use the online Bitrate Calculator, but I guessed the one provided with TMPGEnc would be good as well.
I usually select the Format to be DVD compatible, set the audio to be 448, select the Elementary Stream Audio+Video option, then I use the calculator. The audio part is just for calculating final size, since the AVI is soundless.
Im doing a DVD9 AVI, so I select the final size to 8.5GB, and pull the total final desired size to around 8100MB. The VBR 2-pass for a 2 hour movie is around 7800 kbps, and the predicted final size is around 7.5GB.

But when it finishes, the total size varies a lot from source to source (that might depends on movie having more or less action scenes), and is often quite below the predicted size (5.5GB, 6GB, etc), making me waste a lot of space on DVD9. While TMPGEnc Xpress is encoding, it does reserve a file with the size it calculated. But sometimes, the finished M2V even ends up being smaller than source AVI.

Question is: am I losing quality? This doesnt seem to be happening with CBR, and I could set the values to fit a DVD9, and the result seems to follow the original calculated size.

Example from a AVI I just encoded:

- Original AVI: Size: 5.89GB; Bitrate: 6528 kbps
- Predicted Values: Size: 7.5GB; Bitrate: 8313 kbps
- Final M2V: Size: 5.60GB; Bitrate: 6214 kbps

Perhaps this is ok, since the final video can't have a higher bitrate than the source(?)

If someone can clear it up, I'd appreciate

[whatsmyname]

I think tmpgenc have a target output preset where if you select "DVD 8.5GB UDF", the resulting file is likely to be around 8GB - 8.2GB.

[Taeran]

Yes, that's the option I use.

[whatsmyname]

Maye reinstall it. I never experienced that issue with tmpgenc when I used it.