Electronic Music mailing list archives

Hi,=0AI have written a phase vocoder, and would like to store the data on d=
isk in this representation.=A0 I'm using an overlap of 4, and the number of=
 bands can be either 128, 256, 512 or=A01024.=A0 I've found that using 10 b=
its to represent the amplitude and 6 bits to represent the=A0deviation from=
 the bin frequency gives good quality results.=A0 Currently the phase vocod=
er data uses up twice as=A0many bytes=A0as the equivalent audio file (at 16=
bit, 44kHz).=A0 I would like to compress it down so that it uses about the =
same amount of space as the audio file, in such a way that it sounds indist=
inguishable or very similar to the original file.=A0 I would like the decom=
pression algorithm to be very fast, and would like to implement the compres=
sion in a couple of days coding time at most.=A0 =0AI've searched on the we=
b for any relevant information, but have come up with a blank so far.=A0 Ca=
n anyone point me to relevant information about this problem, or alternativ=
ely give me the benefit of their experience?=A0 =0AThe things that I was th=
inking of trying were storing an amplitude gain per time instant, so that f=
ewer bits could be used to represent the amplitude component.=A0 Also, I wa=
s considering assigning different numbers of bits to amp and freq depending=
 on the frequency of the bin, on the assumption that higher frequency bins =
could be represented less accurately.=A0 I was also wondering whether it mi=
ght be possible to store amplitude data less frequently in either the time =
or frequency dimension for higher frequency bins without noticeable degreda=
tion in quality.=A0 I was also considering using ADPCM with uLaw compressio=
n to compress both the amplitudes and frequencies.=A0 If anyone has any tho=
ughts on how well they think any of the above might work, I'd be very grate=
ful for your thoughts.=0AThanks=0ABen
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