[GEM-dev] vertex_array branch

[guenter geiger]

On Thu, 26 Aug 2004 zmoelnig at iem.at wrote:
> > Ah, sorry then. I have to admit that I haven't used that for a long time,
> > and I could vaguely remember that in order to get a waterfall display
> > with the new pix2sig you had to use a large blocksize with overlap, which
> > in theory should reduce the performance "overlap" times.
>
> i don't quite understand the last sentence.

hmm, thats probably because it isn't really understandable, sorry :(

I really can't remember exactly, but I had the feeling that in order
to achieve the waterfall effect you had to use a certain overlap factor.
This makes it slow. I don't think that the conversion from
float to int at a rate of 44kHz can do the performance much harm.

On the other site, the original sig2pix external was optimised for just
doing that, a waterfall. This was done by having a buffer twice as large
as the image and filling this with the audio data, line per line. Each
time a new line was added, the image scrolled by one line. This was done
by repositioning the image pointer only. Each turn around there was an
additional copy of the whole image.

Well, probably something like this should be called pix_waterfall~
already.

Guenter

>
> however you are right; [pix_sig2pix~] uses huge blocks which will get peaks in
> performance.
>
> mfg.ca.srtz
> IOhannes
>
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