[MPlayer-users] Encoding quality advices

[Robert R. Wal]

On 02.11.28 Moritz Bunkus pressed the following keys:

>          $videobitrate * 1000       
> $bpp = -----------------------
>        $width * $height * $fps

Well, I came to similar equation going through different route. Only I
didn't use bits per pixel, in my case it was bits per block (BPB). The block
is 16x16 because lots of software depends on video width/height being
divisable by 16. And because I didn't like this 0.2 bit per pixel, when
bit is quite atomic ;)

So the equation was something like:

                 bitrate
bpb =           -----------------
       fps * ((width * height) / (16 * 16))

(width and height are from destination video size, and bitrate is in
bits (i.e. 900kbps is 900000))

This way it apeared that the minimum bits per block is ~40, very
good results are with ~50, and everything above 60 is a waste of bandwith.
And what's actually funny is that it was independant of codec used. The
results were exactly the same, whether I used DIV3 (with tricky nandub's
magick), ffmpeg odivx, DivX5 on Windows or XviD.

Surprisingly there is one advantage of using nandub-DIV3 for bitrate
starved encoding: ringing almost never apears this way.

But I also found out, that the quality/BPB isn't constant for
drastically different resolutions. Smaller picture (like MPEG1 sizes)
need more BPB to look good than say typical MPEG2 resolutions.

Robert

-- 
Bastard Operator From 149.156.96.35