[MEncoder-users] new doom9 codec comparission

Corey Hickey bugfood-ml at fatooh.org
Thu Dec 8 22:55:28 CET 2005

Corey Hickey 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
> posterity.

Here are the results for adding qns to the second pass.

without qns: 184m54.632s
with qns=2:  401m13.102s


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