[FFmpeg-devel] [Brainstorming] sound reproduction with a 3 voice soundchip

Tobias Bindhammer tobias.bindhammer
Mon Feb 28 11:42:00 CET 2011

After playing around with video codecs to enable video playback on a
c64, it would be nice to have also sound for that. There would be some
options to reproduce sound via the soudnchip, for e.g. by putting 4 bit
samples at a high rate into the soundchip, however that will cost too
many cpu cycles needed for video playback. So i did efforts with a FFT
and waveformdetection upon the transformation. Target was, to make use
of the three oscillators of the soundchip and just update their base
parameters a few hundred times per second. The result so far was poor,
but spoken words could be recognized. I am not too much into audio
stuff, but maybe some of the audio wizards and gurus can give me some
hints and ideas on how to get fair results (or completely make me drop
this, by saying: no chance :-) )
To represent the original i'd have 3 oscillators at hand, waveforms
would be selectable per channel with sawtooth, triangle, pulse (16 bit
pulsewidth can be set up) and noise. All channels have a ADSR envelope
as well as filters like low, high and band-pass. The oscillators can be
synched and ring-modulation is possible. So any hints on how to misuse
what feature are very welcome :-)
Some basic information on the chip can be found here for example (6581):


Dipl. Ing. Tobias Bindhammer
Institut f?r Verteilte Systeme
Oberer Eselsberg          Phone: + 49 731/502-4235
Universit?t Ulm           Fax  : + 49 731/502-4142
D-89069 Ulm               mailto:tobias.bindhammer at uni-ulm.de

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