[MPlayer-users] [BUG] ratecontrol.c:693: ff_rate_estimate_qscale: Assertion `pict_type == rce->new_pict_type' failed.

[Corey Hickey]

Corey Hickey wrote:
>> btw, something else which seems noone knows about (and i forgot) is
>> -lavcopts aic (does enable ac prediction in intra MBs of mpeg4 ...)
> 
> Hmm. I'd always ignored that based on the description in the mplayer man 
> page:
> 
> aic
>     ac prediction (advanced intra prediction for H.263+)
>     NOTE: vqmin should be 8 or larger for H.263+ AIC.
> 
> The description indicates that it's only for H.263+, which I guess isn't 
> accurate. What does AC stand for? It's hard to find definitions for 
> acronyms like that on google.
> 
> I just did a very quick test, and enabling aic raised psnr from 40.10 to 
> 40.13. I can't look at the video itself from here, but I have a longer 
> test started that might be finished by the time I get home.

Argh, the power went out, so I had to run the test overnight and have a 
quick look this morning.

for i in 1:turbo:vb_strategy=2 2 ; do
   mencoder matrix.vob -nosound -vf crop=718:356:0:60,scale=640:272 \
-sws 9 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=581:psnr:mbd=2:mv0:\
trell:cbp:precmp=2:cmp=2:subcmp=2:predia=2:dia=2:preme=2:v4mv:\
last_pred=2:vmax_b_frames=2:qpel:sc_factor=6:\
vrc_eq="(tex+10^8*mcVar)^0.6":vpass=$i -ofps 24000/1001 -o default.avi
done

Pass 1:
PSNR: Y:40.48, Cb:44.46, Cr:44.83, All:41.48
user    110m12.246s

Pass 2:
PSNR: Y:42.20, Cb:45.25, Cr:46.04, All:43.07
user    174m14.320s


Now, adding aic to the above options:

Pass 1:
PSNR: Y:40.48, Cb:44.47, Cr:44.83, All:41.48
user    110m35.194s

Pass 2:
PSNR: Y:42.22, Cb:45.26, Cr:46.06, All:43.09
user    176m34.086s



Visually, I couln't see much of an overall difference. I only had time 
to look at two scenes, though. On the first scene, many frames of the 
aic encode looked very very slightly worse. On the second scene, several 
frames of the aic encode looked somewhat better and one or two looked 
very slightly worse. Both of these are probably due to the normal 
variation induced by adding an option; I don't think they're indicative 
of any actual change in visual quality.

With encoding times that close, the difference can be largely due to 
experimental error. Just now, I ran several short encodes with default 
lavc options (besides vbitrate) and found that aic consistently slowed 
down mencoder by 1%. ...which actually matches the difference shown 
above, though that might be a coincidence. I wouldn't expect aic to make 
as much of a difference when several other options slow the encoding 
down by a much larger factor, so I did a short test of that as well, and 
found there to be no consistent change.

Since aic seems to improve PSNR, albeit slightly, and only slow the 
encoding down by a negligable amount, I would say there's no reason not 
to use it.

Michael, I'd like to change the mplayer man page description of aic. 
Currently it only mentions h.263+, and we know it works for MPEG-4. Are 
there any other lavc encoders that support aic?

-Corey