[LONG] new results & bugs report (was: Re: [MPlayer-dev-eng] lavcopts PSNR comparison) [ENGLISH]

[Romain Dolbeau]

Jan Knutar wrote:

> I've had interesting results wrt PSNR with the *dia functions. I used a 
> range from -3 to 2, when testing with a similar script, iirc.

D Richard Felker III wrote:

  > Yes. qprd is definitely useful. mv0 and cbp might also be good. Also
  > different choices for *cmp... Can't think of other important ones..

I've tried again, with some more options, on the same scene.

Common options: "vcodec=mpeg4:vqmin=2:vqmax=31:keyint=125:vbitrate=650:psnr:"
video filters: "-vf crop=720:432:0:72,scale=544:230"
(audio was -ovc copy, and output file /dev/null ;-)

The other options were:

vme: 1, 4 (I hadn't noticed that the man page says "0 to 3 is low quality" :-( )
{pre,,sub}cmp: 0, 1, 2, 3, 6
{pre,}dia: 1, 2, -1, -2, -3
vmax_b_frames: 0, 1
mbd: 1, 2
qpel or nothing
mv0 or nothing
qprd or nothing
v4mv or nothing
trell, trell:cbp or nothing

That was 9600 combinations. The bad news is that only 5634 of
those outputed a PSNR value. As soon as the jobs started, some
crashed with a segmentation fault, so i guess it was useful
at least as a stress test... For the record, that binary
was configured & compiled on a bunch of dual 2.8 Ghz Xeon,
running an unknown rpm-based distro (I'm not the admin),
with kernel "2.6.5-1.358smp" and compiled with
"gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)" (I guess
it's a Redhat, then ;-). The running machines were the same.

One picked at random: the combination
"vme=1/cmp=0/precmp=0/subcmp=0/dia=1/predia=1/vmax_b_frames=0/mbd=1/qprd/v4mv"
died on the first frame. Is there something dumb with that combination ?
Or is it a straight bug ?

Of the finished result, the best of the best was:
vme=4/cmp=3/precmp=3/subcmp=3/dia=-2/predia=-2/vmax_b_frames=1/mbd=2/qpel/mv0/v4mv/trell

Of course the results need to be examined more carefully than
with "sort", as in the top 10 alone figure 3 *cmp, all 5 *dia,
both b_frames (although with a 9:1 advantage to 1). mv0,
trell, qpel and v4mv are always there, with vme=4 and
mbd=2. In the top 25, cbp is there 3 times near the bottom,
and b_frames is less clear-cut. qprd isn't there, but
as over 60% of the result with qprd are missing...

Speaking of that, it seems that there's no result for
"mbd=1 & qprd". I guess there's a problem here, assuming
the combination is legal (the man page doesn't say otherwise).
That's 2400 failures accounted for...

More interesting: "vme=4" has 3528 results, only 72 short
of the 3600 one would have after removing the 1/4 "mbd=1 & qprd".
Guess vme=1 is more of a problem (2106 results). With vme=4,
those 72 failures happened "*dia=2 & *cmp=1 & qpel". Is that
an invalid combination ?

(I haven't checked where "vme=1" fails).

-- 
Romain Dolbeau

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