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Topic:		now I'm stumped
Author:		doom9
Posted:		 2001-04-03 15:13
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Hi there

You might remember my earlier opendivx quality comparison
(http://www.doom9.org/opendivx.htm). I'm running another test now,
comparing many codecs and new encoding methods and I've come across
something which is really surprising. First of all I used the latest DS
filter with filtering turned up to the top. I kept the file I initially
made for the first quality check.. an 1800kbit/s file that is. Now I
created 2 new files: 900kbit/s and 6000kbit/s both at the default
settings (btw.. I miss some documentation on these settings . And guess
what... these encodings look good even in the scenes where my previous
articles showed the codec fail miserably.. so far I've only checked the
900kbit/s and parts of the 6mbit/s file but there's no problem I can see
so far. Then I went back to the 1.8mbit/s one and guess what.. it still
sucked. So I redid the clip.. and I just had a look at the scene with
the fast zoom into the weapon racks (4th screenshot in my article) and
that file still looks worse than both my 900 and 6000 kbit/s file. 

Clearly.. the question to ask is "why?". I'd really appreciate if the
developers could get back to me on that issue.. I'll keep the 1.8mbit/s
opendivx on hold and work on the rest of the comparison but I think it's
an issue which deserves close attention.

Doom9


Topic:		now I'm stumped
Author:		eagle
Posted:		 2001-04-03 15:49
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So, OpenDivX at 900kbps looks better than 1800kpbs!?!? Just think how
good it would look at 0kbps!

Seriously though, this sounds like a quirk of the rate control.  Rate
control systems can be complex beasts and are often non-linear.  Is the
1800kbps clip consistently bad, or does it only look bad at the
particular frames that you are comparing?

We'll get to the bottom of this!


Topic:		now I'm stumped
Author:		doom9
Posted:		 2001-04-03 16:10
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according to my impression I`d say that the 900kbit/s clip consistently
looks as least as well as the 1800kbit/s clip.. and the higher bitrate
one screws up pretty badly in all these scenes mentioned in my article
where the low bitrate clip (and the 6mbit/s clip) look good overall.


Topic:		New Codec On The Block (SBC)
Author:		Essbesteck
Posted:		 2001-04-03 17:16
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I can't wait to test it! One question remains:

Does it work with DivX 3.2 (which seems to be some sort of hacked
'union' of FastM and LoM and has VKI, too)? Or do I have to go back to
3.11?

BTW, it's great that we won't have to turn to M$'s dreadful WMV8 and its
utterly incompatible codec and encoder for true VBR two-pass encoding
now after all! 

Thanks!

EB


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