[Theora-dev] Problems with Theora DirectShow filters

illiminable ogg at illiminable.com
Wed Sep 15 09:10:04 PDT 2004

----- Original Message ----- 
From: "Timothy B. Terriberry" <tterribe at vt.edu>
To: "illiminable" <ogg at illiminable.com>
Cc: <theora-dev at xiph.org>
Sent: Wednesday, September 15, 2004 11:15 PM
Subject: Re: [Theora-dev] Problems with Theora DirectShow filters

> illiminable wrote:
>> For the moment... you'll need to find a colour space converter that can 
>> do the conversion properly. In the next release i'll include the RGB to 
>> YUV conversions. I know there are some proprietary filters out there... i 
>> haven't had much luck finding a good free colour space converter though.
> I'd warn against blindly applying someone else's Y'CbCr to R'G'B' 
> converter. There are multiple Y'CbCr color spaces (and in fact, there are 
> multiple R'G'B' spaces, though on a PC you can perhaps assume sRGB 
> support). The available Y'CbCr spaces used by Theora are well-specified; 
> there is a well-defined conversion into device-independent CIE XYZ space 
> (and from there to any R'G'B' space you want). See Secton 4.1 of the spec. 
> However, I don't know what support the Windows APIs have for describing 
> the different spaces.

Doesn't only one of the input colourspaces to theora work ? I dunno where i 
got that impression from... but i thought only the 4:2:0 YUV input worked at 
present ?

There's about 30 or so different YUV and RGB colourspaces specified in 

While i see the value in converting through a known format as a middle 
man... i'm not sure in practice that's all that efficient... there's enough 
buffer copying as is with the current formats.



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