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

[D Richard Felker III]

On Thu, Jun 10, 2004 at 11:56:23AM +0300, Alexei Khlebnikov wrote:
> 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.

AVI container is 24 bytes per frame. Video is typically 24, 25, or 30
frames per second. Audio is 38 frames per second, IIRC. So that gives
about 62*24=1488 bytes per second, or 8976 bits per second,
approximately 9 kbps. OGM is something like 10-11 kbps. MKV is
probably around 2-4 kbps and NUT is about 1 kbps (or less).

Rich