[ogg-dev] Xiph QT Theora Codec

Ralph Giles giles at xiph.org
Mon Dec 19 12:50:22 PST 2005

On Mon, Dec 19, 2005 at 02:09:56PM -0500, Anders Kirchenbauer wrote:

> Taking a look ahead at your QT (OSX version) work, you have Theora  
> Encoding and Decoding on the list.  This could be very beneficial as  
> many times the only way to get a constant frame-rate out of QT is to  
> export (and for DV video recorded in QT, this can be a large issue).

Yes, the ability to export Ogg Theora (or even vorbis+vp3 in .mov) from 
quicktime applications has for a long time been a major limitation for 
the format.

> Another major issue is that the video coming from DV (at least the  
> sources I have used) is almost always interlaced, and since there is  
> no deinterlace in the filter options (not to mention lack of a filter  
> chain), but the codecs seem to be the best way to put a deinterlace  
> into it prior to actual encoding of the frames.

Hmm. So we need to include a deinterlacing filter in the theora 
component? Does CoreVideo help at all with the filter chain issue?

>                                          Due to the DV not going in  
> at a constant 29.97, the audio desyncs, so I have to export the  
> initial DV to another DV with a normalized FPS of 29.97.

How does that work? I thought DV was always fixed framerate. I do 
understand that quicktime is natively fixed framerate (in fact we 
occasionally get complaints in the other direction, because theora
can't perfectly reproduce the variable framerate video from cheap
webcams and capture cards with sloppy sync.)

Otherwise, yes, not being able to do direct encoding from your source
is always painful. Have you tried ffmpeg2theora. I don't think it
talks to quicktime, but it should be able to handle dv input.


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