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

Corey Hickey bugfood-ml at fatooh.org
Mon Dec 12 05:44:26 CET 2005

Michael Niedermayer wrote:
>>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.
> one way to check that would be to cut out a short part of the mpeg2 bitstream
> of both and compare them in some player side by side ...

Yeah, I suppose it's come to that. I've placed a 200MB clip from the
beginning of mine at:


Doom9, if you read this, could you please do the same with as much as
you're comfortable? 200MB is more than enough. Also, feel free to send
me the URL in a private email.

Meanwhile, I'm going to continue trying to find a more generic way to
work around the lack of first-pass ratecontrol. I should have done that
in the first place...

>>>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
> hmm, IMHO no

Yeah. My experiments after I sent the last email seem to show that
vqscale overrides both vqmin and lmin.

>>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?
> if qscale=2.15 is significantly below the target then =2 will be too, and
> lmin has a default of 2 IIRC so i dont think the second pass will reach
> the target size no matter what you change in the first pass

Yeah, I didn't realize that the vqmin and lmin defaults would be too
high until a few minutes ago. I'm starting to think that maybe I should
do this:

First pass:  vqscale=1
Second pass: vqmin=1:lmin=1:vbitrate=581

I'm testing this now...


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