vbr_max_brate explanation

[magic144]

hi guys,
good to have a fountain of knowledge here on the internet, eh?

just wondering if anybody knows how vbr_max_brate is calculated
I read somewhere in these forums that it was 9000-AudBitrate

but there must be more to it than that
I'm looking at a Prepare'd ECL file here that is keeping 1 Audio track (5.1, i.e. presumably 448Kbps), but vbr_max_brate is still listed as 9000

what is the missing link?

cheers

m

[manono]

9800 for video only. 10800 for video, audio, subs, and muxing overhead.


[Manano: Sorry, I edited this message thinking it was mine, I set it back.]

[magic144]

well yeah,
but it's 9000, not 9800

isn't there a formula?
perhaps it's 9448-audio

presumably it's 9000 and not 10800-448-muxing to avoid bitrate spikes which are non-compliant

I know the Bitrate Calculator seems to use a max video bitrate of approximately 9800-Audio, but I've also read that 9000 might be a better high-water mark, and indeed less for higher/highest player compatibility?

[jdobbs]

In DVD-RB the maximum bitrate is never higher than 9800 minus the sum of the combined audio bitrates. But can, however, be set lower on occasion based upon requirements (e.g. ILVU). The default value for maximum bitrate is 9000 (when there isn't another value in the INI file).

So, for example, if you had a set of audio tracks that combined added up to less than 800Kbs -- the maximum would be set to 9000.

The DVD Standard says video can be up to 9800 as long as the combined video/audio/subpicture doesn't exceed 10080. If a player has problems with that -- it should be sent back to the manufacturer as faulty, because it shouldn't have the DVD symbol on it.

[Correction] Wasn't thinking, the maximum combined bitrate is actually 10.08Mbs and I'd written 10800, fixed it...

[magic144]

I gotcha

cheers for the info
I was just wondering, so I could reproduce similar quality encodes of material when I'm not using DVD-RB (perish the thought!)

seriously tho, I was using a workflow with DGPulldown to do a PAL-NTSC conversion, and it worked pretty well (I was using the Bitrate Calculator to determine the max bitrate setting, and hence had wondered how DVD-RB decided upon this value)

thanks again!

[manono]

Darn, I said 10800, where I meant to say 10080. Sorry for the mistake. And yes, DVD-RB uses lower max's, but I thought you were asking for the DVD specs.

[magic144]

well we got there in the end
cheers for the response - this forum is the best (as is the product)