[theora] Question about converting VP3 to Ogg Theora

Dan Miller dan at on2.com
Wed Jul 23 09:43:08 PDT 2003

good question. We had some sort of 'null frame' flag in Windows I think, but I can't recall exactly how it worked... it might have been at the AVI layer.
Of course one can always encode a frame with all uncoded blocks, but that's a bit expensive.  There should be a way to mark a frame as completely uncoded.
Anyway, if this is to be possible at all, we need to get a handle on the upside-down problem as well.

        -----Original Message----- 
        From: Colin Mckellar [mailto:c.mckellar at student.murdoch.edu.au] 
        Sent: Wed 7/23/2003 10:57 AM 
        To: theora at xiph.org 
        Subject: [theora] Question about converting VP3 to Ogg Theora

        As I understand it the current plan is to make it possible to
        losslessly transcode VP3 video to Theora video.
        In my experience, one of the "features" of VP3 is it drops frames in
        the event that there is little/no movement in a frame, or if "drop
        frames" is enabled, to drop frames if the data rate is getting too
        high. I understand that the way that VP3 does this in QuickTime is it
        changes the duration of the previous frame. The Ogg format does not
        allow for variable frame durations. What are the plans to reconcile
        this disparity?
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