[PD] raw audio format and open files randomly

Roman Haefeli reduzierer at yahoo.de
Mon Jul 6 09:41:56 CEST 2009

On Sun, 2009-07-05 at 12:46 -0400, Martin Peach wrote:
> nick burge wrote:
> >  Hello list.....Intrigued by the idea of playing back jpeg (or other) files
> > as audio signals I've been having a go with the readsf~ and soundfiler
> > objects....skipping the header with readsf~ and using the -raw flag in
> > soundfiler, opening in an array and using tabplay~ to play it back....whilst
> > I can get these objects to open the files and play them back, the results
> > seem a bit disappointing...just a lot of white noise at a constant volume.
> > The wave forms displayed in the array look more promising than the audio
> > result
> > Was I expecting too much? What else could I be doing to achieve a more
> > interesting sound?
> Jpegs are usually compressed and compressed data looks like white noise. 
> Maybe try uncompressed images with regular patterns in them, or low-pass 
> filter the sound.

or try single-channel files (black&white) instead of coloured files. 

depending on how you read the files and what bitdepth you assume
(8/16/24/32bit), the same files is going to sound much different. let's
say, you read a plain 3-channel rgb uncompressed image file
(uncompressed tiff or bmp), where each channel has a bit depth of 8 bit,
and you open such a file, while specifying 24 bit per sample, then your
hearing sensation would almost only be influenced by the most
significant byte (so to speak: by one of the three color channels). in
order to treat all the channels the same, you would need to extract each
channels first.

as a start, it might be easier to play with only black and white images.
the problem here is, that you cannot tell [readsf~] to assume 8 bit
input. however, you could read it as 16 bit input and then extract the
lower and upper 8 bit from each sample and write the resulting two
samples to another array.

rendered images containing simple gradients might sound less like pure
noise than real photos. due to how many image formats are encoded, the
width in pixel might correspond with the base frequency of the resuling
sound, so this might be an important parameter to play with as well.

yo, tell us, if you can come up with something 'interesting'. i'd be
interested to hear and see.



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