[MEncoder-users] new doom9 codec comparission

Corey Hickey bugfood-ml at fatooh.org
Thu Dec 8 07:34:19 CET 2005

Corey Hickey wrote:
> Rich Felker wrote:
>>>----docs --------mine---------------reason-----------
>>>last_pred=3    last_pred=2   slower, no difference
>>>vb_strategy=1  <default>     lower PSNR, worse quality
>>>qns=2          <default>     too slow for this test
>>qns may be slow, but it's the best perceptual-quality improvement that
>>doesn't show up in psnr results. you really should test and see,
>>because it might make all the difference!
> Yeah, I like qns too. I tested it extensively when Michael first wrote
> it, so I know what differences to look for. I wasn't able to see very
> much of an improvement, though, so I figured it wasn't worth sacrificing
> that much encoding speed.

Upon re-reading that third sentence, I realized I worded it wrong. I
should have said, "When testing qns=2 for this comparison, I wasn't able
to see much of an improvement,".

Trouble is, the postprocessing eliminates most of the ringing artifacts
anyway, so the benefit of qns is masked. The difference is still
visible, but so subtle that I doubt anyone would notice unless they
already knew what to look for and where to find it.

> I'm re-testing qns=2 right now with my current
> parameters, including threads=2 (see below), to see if it works out any
> better this time.

The encode still isn't finished, but I've viewed several parts already
and my conclusion is that it just isn't worth it for this comparison. I
still like qns=2, I'll keep using it myself, and I will still recommend
it in general when speed isn't much of an issue. Since speed is a factor
in Doom9's evaluation, though, I have to leave it out for now. qns=1 is
barely faster, so I don't think it's an acceptable compromise either.

I'll let the encode finish some time tonight and report the results for


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