[Theora] Ffdshow-20042003 Theora support fixed.

Neil Morris neil at adm1.ph.man.ac.uk
Mon Oct 11 04:25:21 PDT 2004

Hi Zen,

At 12:45 09/10/04 +0800, you wrote:

>----- Original Message ----- From: "Neil Morris" <neil at adm1.ph.man.ac.uk>
>To: <theora at xiph.org>
>Sent: Thursday, October 07, 2004 4:51 PM
>Subject: [Theora] Ffdshow-20042003 Theora support fixed.
>>Thought I'd pass this along for Theora users on the Windowzz platform.
>>The latest alpha build of the ffdshow filter (20041003) on Sourceforge
>>Seems to have had theora, broken since the June/July unofficial builds,
>>fixed. This build also connects nicely to Zen's Ogg splitter and also
>>decodes Helix Producer encoded Ogg's well. The encoder side though still
>>only outputs Theora frames to AVI.
>Excellent news ! I always wondered why they just all of a sudden stopped working... probably some change that i made... but i wasn't sure what.
>As to the encoder... is the reason that it only outputs to AVI, that it converts to directshow time ? (And my muxer wants granule pos)

I've never delved into ffdshow source so I couldn't tell if this was the
reason but I'm currently wading through the Ogg/Vorbis/Theora documentation
and trying to get to grips with "granule pos" and I would guess that IS 
the reason<g>.

I'm new to A/V programing and Theora/Ogg but I'm interested in trying my 
hand with something to familiarize myself with Xiph formats, so I have 
been toying with the idea attempting to writing a program to convert the
ffdshow avi theora files to ogg as a learning exercise, and as my 1st 
programing language is Fortran it should make the code very "interesting"<BG>.

>This was something i struggled with for a while... i really wanted to just pass directshow times throughtout all the graph... but because theora actually has other information embedded in it's granule pos, if you convert it to a directshow time, you can't recover that information. So i ended up deciding to pass granule pos everywhere, and leave the responsibility to any filter that connects to a filter outside my little ecosystem to make the conversion.

As I've mentioned I'm very new to Theora and Ogg and still working my way
up the learning curve but I have grasped enough so far to appreciate your

Best Regards and looking forward to further releases of your filter set.


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