[PD] GEM error on latest pd extended with Ubuntu Gutsy

Roman Haefeli reduzierer at yahoo.de
Wed Oct 31 03:29:44 CET 2007

On Tue, 2007-10-30 at 13:38 +0100, Thomas Mayer wrote:

> Maybe the video is corrupt, have you tried transcoding the video with
> mencoder or transcode?
> Try
> $ mencoder -ovc xvid -xvidencopts bitrate=800 -oac copy -o train.avi
> train.mov
> and load the film train.avi

hi thomas

maybe i missed something, but i don't quite see why you are suggesting
to reencode the movie to avi-container with xvid codec. usually it is a
bad thing to do, because xvid codec, that is quite heavy cpu-wise to
decode (ok, on decent computers it is not that much an issue anymore),
and - what is much more important - it is a so called interframe codec,
which means, that many frames are dependent on each other. this
basically means, that the codec is optimized to be played only forward
and at 1x speed. playing at a different speed or backwards can either
produce funny artefacts or not work at all. usually when using a video
in gem, having high flexibility and low cpu cost is much more important
than small file size. that is why so called intraframe codecs are rather
recommended for this kind of task. 'intraframe' means, that each frame
is encoded separately, which makes it very easy to access and render
random frames. i think most supported intraframe codecs are 'jpeg',
'mjpeg' and 'dv'. 
yo, i am not very much an expert in this field, so i might be not very
precise in everything, but i hope i could give some idea, why generally
you rather not want xvid as movie codec to be used in gem (although you
are especially looking for funny effects).


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