[Theora-dev] Problems with Theora DirectShow filters

Robert Huitl theora-dev at huitl.de
Sat Sep 18 09:12:08 PDT 2004

On Friday 17 September 2004 10:49, illiminable wrote:
> >You can download it at www.huitl.de/theora-speex-mux.ogg.
> This has no video frames in it !! Also... since seeking takes place on the
> first stream... you should really have theora as the first stream in the
> file (this means on the bottom pin of the muxer)... it doesn't matter too
> much for now... but when i do keyframe seeking it might.

Well, my code connects the theora encoder to the muxer first, and then the 
audio encoder. Should I do this in reverse order and add the first stream 

I put another file online at http://www.huitl.de/theora-only.ogg. As the name 
says, it's only a theora stream, captured from the webcam and color-converted 
by ffdshow. It plays in GraphEdit (but not with the ffdshow MPEG4 filter), 
but it looks to fast and the graph causes a time-out at the end.

> I suspect the problem is that the ffdshow filter strips the granule pos
> time stamps, and attaches it's own... which are in directshow time... which
> are significantly higher numbers (1 sec = 10,000,000 UNITS), so when it
> muxes, all the theora frames will be bunched up at the end. Potentially
> even an overflow could occur.

I didn't understand this one completely, but it sounds reasonable :)
With the ogg-file mentioned above, you should be able to find out if this is 
the case.

> >P.S.: In case you can't get audio/video working, the resolution is
> >320x240/RGB24 at 30fps (at least, that's the setting. Don't know if the
> > webcam can supply that much with USB 1.1).
> Ok... was just checking... as i have noticed a bug when the resolution is
> very high... in particular where you have a very wide, but not very tall
> frame... i'm not sure if that is occuring in my code or in theora at this
> stage. But that resolution is certainly within the range that i have
> previously tested.

-> http://www.huitl.de/videocap-playback.png
There are two resolutions in the filter graph properties, 320x240 and 384x240. 
Though it might not be a problem, it looks strange to me.

> PS: Could i also ask (i'm not sure if it was accidental or not)... that
> except for private correspondence (or where you want to keep specific
> information off the list), you keep as much of this on the list as
> possible... it makes it easier to capture the information and make it
> available to everyone who may be encountering similar issues. Cheers.

Sure. I forgot to set up a correct reply-address for postings to this mailing 

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