[MEncoder-users] new doom9 codec comparission (submission)

Corey Hickey bugfood-ml at fatooh.org
Mon Dec 12 03:31:48 CET 2005

Michael Niedermayer wrote:
>>>>Without being able to test your source directly, I would suggest using
>>>>vqscale=1.5 instead of vqscale=2.15. Don't take that to be my final
>>>>answer, though; I'm hoping to get some insight from other people on
>>>>mencoder-users. vqscale=1.5 is based on looking at a graph I have of
>>>>quantizer vs bitrate for snow, and erring on the low side (1.8 is my
>>>>closest guess, but 1.5 should be safe).
>>>Well, you can use AviSynth with Wine, and decode the AviSynth script via 
>>>avs2yuv.. I think dgindex also works on Linux if you don't have a windows 
>>>box to test.
>>I would try to do that, but I really don't have time right now... :(
>>I'll see if I can tomorrow, but it might be too late for you.

Well, I managed to get my laptop (running windows right now) set up
encoding from the avisynth source, using the same script and parameters
as Doom9. It's going to be a few more hours before it's done, but I
don't think there will be a significant difference in bitrate from the
test encodes I did under Linux. I've been "following" my laptop encode
with my desktop machine, and at all the intervals I checked the bitrate
was the same +/- a few percent.

Assuming that I've reproduced the same environment as Doom9, that likely
means the DVD I used is different, somehow. Maybe it's more grainy.

> i would guess that lmin was too large, though its not clear how it could
> have worked for corey ...

Does lmin have any effect on the constant-quantizer first pass? I'm
figuring that if the first pass hadn't used such a low bitrate, then the
second pass would have used the specified bitrate.

Doom9 pass 1: 479.429
Doom9 pass 2: 519.393

   my pass 1: 592.388
   my pass 2: 581.367

Right now, I'm testing whether it would work fine to ask Doom9 just to
use vqscale=1 for the first pass, which is way lower than what it needs
to be. If that ends up working fine, it's an easy solution that also has
the benefit of not needing to be adjusted for different encodes (except
for very-high-bitrate ones).

Any comments?


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