[theora-dev] variable frame rate for Theora

Timothy B. Terriberry tterribe at email.unc.edu
Wed Nov 12 04:44:28 PST 2008

Ralph Giles wrote:
> There is a work around. Duplicating the previous frame is relatively
> cheap, so an encoder could set something like 5 fps, but only update
> the image when there's a change. The current encoder isn't smart
> enough to do this automatically, but a screencast app could force it.

To clarify, a dropped frame in Theora takes up zero bytes, plus Ogg
framing overhead, which is on the order of one byte. The current encoder
actually always writes out a full frame, but if the video data doesn't
actually change, these are still extremely small (just a few bytes).
Both approaches are on the order of what it would take to add extra
timecodes to each frame to indicate the variable duration in a variable
framerate system (for reasonable framerates).

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