theora - Nov 2008 - video files contain one frame more than encoded

Hi,

ogg/theora files produced with libtheora-1.0, according to mplayer,
contain one frame more than encoded, and the last two frames in the
file are at the same time (correct time of the last encoded frame).

Is that normal or maybe a bug or a mistake in encoding?

If it should be normal: What is the reason? Can it be prevented? How
is the relation of the nominal time of the frames in the file to the
time at which the encoded frames were aquired --- is there some
interpolation in time? I need to know the real time corresponding to
each frame in the file ...

Olaf

On Wed, Nov 19, 2008 at 2:49 AM, Olaf Till <olaf.till at uni-jena.de>
wrote:
> ogg/theora files produced with libtheora-1.0, according to mplayer,
> contain one frame more than encoded, and the last two frames in the
> file are at the same time (correct time of the last encoded frame).
It could be a bug in the encoder, or a bug in mplayer. Without seeing the
file, it's hard to say.
> If it should be normal: What is the reason? Can it be prevented? How
> is the relation of the nominal time of the frames in the file to the
> time at which the encoded frames were aquired --- is there some
> interpolation in time? I need to know the real time corresponding to
> each frame in the file ...
Theora is a fixed-framerate codec; libtheora expects to be handed
regularly spaced frames and encodes what it's given as if that's the
case. Sometimes that means the driving encoder needs to do temporal
jitter or interpolation if the original source was not fixed
framerate.

 -r