[Matroska-devel] Re: Ogg and Vorbis/Speex/FLAC directshow filters

Paul Bryson paul at msn.com
Wed Mar 31 07:53:51 CEST 2004


I was also talking with the CoreVorbis fellows just a few days ago about using a
standard set of GUIDs.  Except that it was more to do with a standard way to
generate GUIDs.  This was for consideration from the Matroska project as
Matroska uses a human readable codec ID.  A list of the current IDs is available
here:
http://matroska.org/technical/specs/codecid/index.html

Here is what has been more or less decided. GUIDs are 128bit (16byte).  So, it
was decided to use the first byte as an ASCII character indicating the pin type
(Audio, Video, etc).  Then you make an MD5 checksum of the CodecID and store the
first 15 bytes in the remaining 15 bytes of the GUID.  In this way you know
immediately what type of connection it is.  Also, source filters do not need to
be updated to know what GUID should be used for a specific codec as they could
generate them on the fly.  Known GUIDs would stay the same.  If a en/decoder
filter could be updated, it is recommended to update it to also connect to the
pin type using the MD5 checksum.


Pamel

----- Original Message ----- 
From: "illiminable" <ogg at illiminable.com>
To: "Paul Bryson" <paul at msn.com>
Sent: Tuesday, March 30, 2004 6:17 PM
Subject: Re: Ogg and Vorbis/Speex/FLAC directshow filters


Hi there... i've been talking to the coreVorbis guys recently... And we were
takling about using a standard set of GUIDS so that they can talk...

At the moment i deliberately chose different ones to a) avoid other filter
sets interfering while they are in testing and b) to stop my filters messing
with anyone elses.

It is my aim to be as compatible as possible eventually... but theres some
intensive testing that needs to be done before letting the different filters
all start talking to each otehr.

Thanks for the feedback,

Zen.






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