[MPlayer-users] RFC: docs update for "how to create a%0A%09high%09quality DVD rip"

[Alexei Khlebnikov]

On Thu, 10 Jun 2004 16:09:35 +1000
"Adam Karkowski" <adz at acon.com.au> wrote:

AK> On Mon, 2004-06-07 at 15:57 -0400, Jason Tackaberry wrote:
AK> > Bv = ((S * 1024 * 8) - (Ba * T * 60)) / (T * 60)
AK> >
AK> > Or, simplified:
AK> >
AK> >        (S * 1024 * 8)
AK> >   Bv = --------------   -  Ba
AK> >           T * 60
AK> >
AK> > Jason.
AK> 
AK> Greetings. This is my first post on this list.
AK> 
AK> I think that formula may be slightly wrong. As I understand it,  
AK> mplayer/mencoder uses 1 kbit = 1000 bits. Therefore, that "1024" in the  
AK> numerator should actally be a "1000".

I think, no. 1024 here is a numerator for KBs, not kbits. S is in KBs, S * 1024
is size in bytes. T is time in minutes (not presize). Bv and Ba are in bps, not kbps.


More correct formula is then:

                        (target size) * 8
(video bitrate) = -------------------   - (audio bitrate) - (container bitrate)
                         (time) * 1000

Here:
bitrates are in kbps
target size is in bytes
time is in seconds

Container bitrate is the bitrate of the container (AVI/OGM/MKV/etc) overhead.
I am too lazy to compute average container bitrate. If anybody is curious enough
to count it on some movies - please post results here. :)
My prognosis for this number is about 15 kbps in average.