Hi Martin,

Thanks for chiming in.  I've received some code from Greg Thompson
(THANKS!!!) which is similar which I will give a try as it's easy for
me to translate to Java code.  I'll also keep your advice in mind!

stevn

On 9/13/07, martin.peach@sympatico.ca <martin.peach@sympatico.ca> wrote:
> Steven Yi wrote:
>
> > It should certainly be possible and I've seen some code here and there
> > and have investigated some but I haven't had a chance to implement.  A
> > while back I had wanted to implement the same method as Ardour (which
> > I think uses a cache file for faster rendering) but I couldn't find
> > it's waveform rendering code the last time I looked.  If I remember it
> > correctly, to show a waveform well it has to do some averaging or
> > peaks for all the sample values that the pixel holds, otherwise you
> > could get really different waveforms if you happen to hit the wrong
> > sample.  I'm not sure what's involved, but if someone knows what is
> > involved and tells me I'm sure it wouldn't be too bad to figure out an
> > implementation.
>
> I did it a couple of times by figuring out how many samples fit into a pixel width, then scanning that many samples for maximum and minimum, then drawing a vertical line between the maximum and minimum points, and repeat for each pixel column. It's also useful to cache either the bitmap image or the list of min/max pairs as long as the scale and data stay unchanged. Some audio apps seem to be doing that in the background whenever they have idle time.
>
> Martin
>
>
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