gordian knot bitrate calculator and undersized avis with AC3 audio

[Petzku]

I've tried to encode several movies with the bitrates that gordian knot calculator gave me but i always end up with a tad smaller file.. Why would that happen?

I'm making the frameserver with gknot and encoding the movie myself with divx5pro and virtualdub because i want to use good resolutions like 640*272 for 2.35 rips.. and that's not possible with gknot resolution chooser.

[manono]

Hi

If you want absolutely accurate file sizes, you'll have to use DivX 3.11 or XviD. As I understand it, with DivX 5.02, particularly when using B frames, it's not possible to get 100% accurate file sizes.

By the way-how much is a "tad"?. If we're only talking a MB or 2, I'd say forget it.

I might suggest estimating the correct bit rate based on what GKnot gives you and your own experience. Then if you come out slightly over sometime, perhaps reencode the end credits at a slightly lower Quant.

And welcome to the forums.

Edit: I forgot to ask: You did click on DivX 5 in the Bit Bate Tab, didn't you?

[Mac Sidewinder]

Edit: I forgot to ask: You did click on DivX 5 in the Bit Bate Tab, didn't you?

Also Gnot will automatically recalculate the bitrate after it transcodes the audio. You will have to perform this yourself if you are using virtualdub manually. How much "undersized" are you talking about? I use gnot with 3.11 and 5.02 and always come within 5mb of the desired filesize. (by using a compression check)

Mac

[llemor]

Yes, Mac is correct. You have to transcode first your audio manually and input the correct audio file size in the bitrate calculator.

Likewise, if you encode credits portion separately, you must re-calculate your bitrate considering encoded credits file size.

[Petzku]

Yes i was aware of those.. But now i'm speaking of 50-60Mb differencies in the final filesizes...

And this also seems to happen with avi's with mp3 audio too..

Oh yes.. and i did select divx5pro...

and also i've done lots of movies with 0.23 and then i did not have any size problems...

[theReal]

There's another possibility:

There is a bug in Gknot with Divx5 for the "calculate avi filesize" setting. Gknot enters another bitrate in the codec settings than you entered in the calculator (I found this out using vdubconf).

So, you shouldn't use the "calculate avi filesize" mode, but only the "calculate average bitrate" mode for a correct calculation.

[HomR]

Originally posted by Petzku
I've tried to encode several movies with the bitrates that gordian knot calculator gave me but i always end up with a tad smaller file.. Why would that happen?

I'm making the frameserver with gknot and encoding the movie myself with divx5pro and virtualdub because i want to use good resolutions like 640*272 for 2.35 rips.. and that's not possible with gknot resolution chooser.

You can use 640x272 or other 2.35 AR compliant resolutions in gknot.

;) :rolleyes: :p