performance question jit.qt.movie, "start" or "time"-message

May 23, 2006 at 3:57pm

performance question jit.qt.movie, "start" or "time"-message

Hi list,

I am wondering. What is actually happening inside the jit.qt.movie object when sending him a ‘start’-message. To me the performance seems to increase when sending ‘time $1′ messages instead.

If I use the standart way in my patch (by using the a ‘start’ message) 30-50% of my CPU is taken already, without even sending any bangs to the jit.qt.movie object for output (I am working with two 1024 x 768 foto-jpeg footages).
But if I use a metro and ‘time’ values that I send to the movie object, I have almost all the CPU-power left. To me it looks as if there is no decompression done just by sending ‘time’ messages.
Is that correct?
When banging the jit.qt.movie object, the difference in performance speed is not that huge anymore but an advantage of a few fps remains.
I’d really like to know a bit more about what’s actually going on in there, because it seems to be an important point if you want to do some tuning while working on the edge of your CPU-Power.

Does it make any sense to work around the usual way of playing a footage by ‘starting’ the movie object or do some problems occur that I haven’t noticed yet?

thanks a lot

.tom

#26122
May 24, 2006 at 11:23am

hi,

for my little experience, the most important thing is when you compress your movie in Photo-JPEG codec is the quality in relation with the speed of the film (the Mb for second).

And if you only need play a film without processing the image you can send a message “window XX” where XX is the name of the jit.window XX, in this way the film will play correctly..

I hope that this information will help you,

albert

#77642
May 25, 2006 at 9:11am

No. Naturally, every frame that is output has to be decompressed. The
difference with your variant is that you, rather than quicktime, are
deciding how often to decompress frames.

Basically, if you find that your method is yielding better performance,
you should go with it. There’s no “right way” to do this. Letting
QuickTime decide everything is the easiest and, in some case, probably
the best (since QT can preload data, etc. based on whatever criteria it
uses). But you have the option to do it the way you like.

jb

#77643
May 26, 2006 at 6:04am

if your really pushing for speed performance check out jit.matrixset or xray.jit.3dbuffer, so that every frame wont have to be decompressed in real time. Takes a good deal of RAM but its worth it.

#77644
May 26, 2006 at 1:12pm

When you use frequent ‘time’ messages to play your movie instead of ‘rate’ (for instance I send a time message every 40 ms because I want to sync a movie to an audio buffer~), make sure you set rate to 0. This increases your performance drastically.

Mattijs

#77645

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