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OpenDivX Forum Digest



Topic:		Not YCbCr420?
Author:		sanhan
Posted:		 2001-02-22 01:02
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It seems the OpenDivX code use YUV411
as the basis of image data, not YCbCr420
recommended in MPEG-4.

Am I wrong in understanding the standard 
or your code? Tell me please.


Topic:		Using CVS
Author:		le.toto
Posted:		 2001-02-22 04:36
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would it be possible to have a link to zip files of the latest update of
the CVS for every project in the CVS tree ?

french version:

bon, c'était vraiment pas clair alors je le refait en français.
il serait bien que, dans la page d'accueil des CVS on puisse télécharger
l'état actuel des differants dossiers sous forme Zippée. 


Topic:		Using CVS
Author:		Junto
Posted:		 2001-02-22 12:38
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Quote:
On 2001-02-22 04:36, le.toto wrote:
would it be possible to have a link to zip files of the latest update of
the CVS for every project in the CVS tree ?


Yes, we're working on that right now.  The sources will be zipped up
nightly and posted.

Junto


Topic:		Speaking of better codecs...
Author:		Brians256
Posted:		 2001-02-22 13:54
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Heejaf, I just sent you a copy of the codec
binary and an INF file to install it.

I've been playing with it and there are three major problems at this
point:

1) the encoded video is upside down.
2) the resolution of the video must be evenly divisible by 64.  In my
modification of the code, I've fixed one of the bugs so that the
remaining bugs only require even division by 32.
3) It's way slow to encode.  Decode isn't too bad.  I have a 550MHz K7.

I'm having more fun playing with this code than with the ProjectMayo
code, because it seems much cleaner.  Also, I don't have wierd problems
with the build.

I can encode with mpeg2avi if the resolution is 640x480, but the image
is upside down.  Also, I noticed some artifacts that I can't yet
explain.[ This message was edited by: Brians256 on 2001-02-22 13:56 ]


Topic:		Speaking of better codecs...
Author:		Heejaf
Posted:		 2001-02-22 14:18
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Thanks for the help 


Topic:		Not YCbCr420?
Author:		Brians256
Posted:		 2001-02-22 17:04
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YUV is the same thing as YCbCr.  However, I don't know the difference(s)
between 4:2:0 and 4:1:1 formats.


Topic:		Using CVS
Author:		elbows
Posted:		 2001-02-22 18:05
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Thats excellent news, Im sure lots of people arent using CVS so are
missing out on the latest developments.

Great work guys 


Topic:		Speaking of better codecs...
Author:		Isibaar
Posted:		 2001-02-22 18:40
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@Brians256:
I also discovered some annoying artifacts especially in the area of
frames which are very bright. Unfortunately I also have no clear idea
where these artifacts come from.

But I played around a little bit with the code and changed it so that
every encoded frame was a key frame. => the artifacts still remained
visible

Then I looked over the dct and idct routines and they seemed to be ok.
So I suppose that there's probably something wrong with the quantizer.
Unluckily I've not the time (and probably not the programming skills) to
work this over.

BTW: the decoding performance for me is quite bad. I am not able to
decode a 640x480 movie in realtime on my athlon 1 GHz (even after I
replaced the standard idct with mmx idct)


Topic:		Not YCbCr420?
Author:		eagle
Posted:		 2001-02-22 19:37
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Someone once explained to me the reasoning behind the nomneclature:
4:4:4, 4:2:2, 4:2:0 and 4:1:1.  I've forgotten it now though but here is
a quick attempt at a definition:

<!-- BBCode Start --><B>4:4:4</B><!-- BBCode End --> Equal number of
samples of Y, Cb and Cr.  This means a frame can be represented by three
arrays all the same size.  Usually only used at the camera or display.

<!-- BBCode Start --><B>4:2:2</B><!-- BBCode End --> The chrominance
components are subsampled by a ratio of two horizonatally.  Used for
MPEG-2 contribution and other professional video.

<!-- BBCode Start --><B>4:2:0</B><!-- BBCode End --> The chrominance
components are subsampled by a ratio of two horizonatally and by a ratio
of two vertically.  Used for MPEG-2 distribution, MPEG-4 and H.263.

<!-- BBCode Start --><B>4:1:1</B><!-- BBCode End --> The chrominance
components are subsampled by a ratio of four horizonatally.  Used for
DV(?)

eagle[ This message was edited by: eagle on 2001-02-22 19:38 ]


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