[MPlayer-users] encoding questions

[D Richard Felker III]

On Fri, Feb 06, 2004 at 06:14:37PM +0100, Amadeus wrote:
> > > Calculate it yourself, it's easy:
> > >
> > > ((size of 700MB CD ~5872025600bits)/(length of the movie in seconds))-(audio bitrate in bps)
> 
> Okay, that is easy!
> 
> > Or:
> > $ dc -e "700 1048576 * `du -b frameno.avi | cut -f 1` - 8 * $SECONDS / 1000 / p"
> 
> Pretty neat! =)
> 
> 
> I have a final question:
> 
> A DVD is encoded with 9000bps in mpeg2 format.
> 
> Are there a rule of thumb what a mpeg2 bps does correspond to in mpeg4
> bps?

IMO it's not worth trying to make the comparison. DVDs use extremely
high bitrates to make up for the fact that the idiots mastering them
don't (can't) crop black borders and don't even attempt to align the
borders that remain, they leave nasty distortion at the picture edges,
sometimes even hard-telecine (which ruins quality), etc. Once you
clean up their mess and rescale to the resolution you want to encode
at, you're in much better shape; lots of the extra 'compression' comes
from this stage, and not actually the mpeg4.

If you were to encode mpeg2 similar to how mpeg4 rips are typically
done (clean-cropped, ~640x272 video with fair denoising), I imagine
you could get similar quality at just 1.5-2.5x the bitrate.

Rich