[sdiy] 12 bits D/A converter?

[Mattias Rickardsson]

On 13/07/07, labolida <labolida at terra.com.br> wrote:
> > >
> > > I'm currently working in a digital synth  http://www.sdiy.org/labolida/
> >
> > Is the sound guaranteed to have as much alias noise as those pictures? ;-)
> >
> Hi Mattias, you are right..! I shamed :-(
> I just have put a better pictures in the page.

They still look the same.

The problem is that browsers (for some extremely stupid reason) never
resize pictures properly, they just throw away pixels - thereby
introducing lots of alias noise, just like when downsampling a sound
file without anti-alias-filtering it first. Mathematically speaking,
the highest room frequencies (which there is a lot of) in the picture
get folded back into lower room frequencies with the new Nyquist room
frequency. It gives graphics jagged edges, and in photos it tends to
turn up as very strong annoying noise. This makes even the nicest
synths look awful. :'-(

The solution is (and this goes to all webby SDIYers out there!) to
NEVER let a browser resize an image. Which means, never use the
'width' and 'height' attribute of the <img> HTML tag (like it is done
with the 'width="450" ' in these pages).

The only good use of 'width' and 'height' is to enter the true picture
dimensions, i.e. to NOT resize it. Then the browser can draw the
correct page disposition directly before loading all the pictures, and
the contents is not moved around while loading. But it's easy to get
these dimensions a bit wrong by mistake, giving an ugly picture...

So, what to do with the 10megapixel image to get it small enough for
the web page? Resize it in a decent image program first. A browser is
definitely not one of them. :-)

Good luck!

/mr