[visionegg] Re: newbie questions about quicktime
- From: Andrew Straw <astraw@xxxxxxxxxxx>
- To: visionegg@xxxxxxxxxxxxx
- Date: Tue, 25 Jul 2006 14:38:14 -0700
Dear Ram,
Ramapriyan Pratiwadi wrote:
> Hi -
>
> I'm developing a demo that consists of playing multiple quicktime
> movies. I have a preliminary version of the demo running, but would
> like to tweak it to run a little smoother... here are my main
> problems:
>
> 1. the movies are of high quality, and on a 12" powerbook, the
> playback is kind of jerky - is it possible to cache to memory, in
> advance, all of the movies i want to show ?
I'm guessing that the jerkiness is due to the decoding of the movie
being near the limits of your CPU power. So, basically want to eliminate
the decoding step. Unfortunately, laptops generally have fairly slow
hard drives, too, so I think you're right that the best bet is to buffer
to RAM.
It is possible to decode the raw frames and save it to RAM for later
playback, although the VE doesn't support that directly (although it
could be implemented...). You'd have to export the movie to an image
stack and then load the images to RAM. See the image_sequence_fast.py
for an example.
>
> 2. in the quicktime demo, are these commands necessary ?
Without going back through and really thinking about each step:
> - screen.clear()
Not necessary, and skipping this could buy you a little time.
> - viewport.draw()
This is necesary as it actually triggers the drawing of each of your
stimuli classes.
> - swap_buffers()
This is necessary as the drawing happens on the "back buffer" and you
want to display that, which means making it the "front buffer". This is
not a computationally intensive job, however, and merely involves
telling the RAMDAC to look at a different place in memory.
>
> 3. is it possible to add noise to the movietexture, in order to
> degrade the quality of the image ?
Yes, you could overlay a texture (with varying alpha for transparency),
or you could manipulate the movie in advance. I'm sure there are other ways.
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