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02 September 2016, 21:54   #9
meynaf
son of 68k

Join Date: Nov 2007
Location: Lyon / France
Age: 44
Posts: 2,459
Quote:
 Originally Posted by Foebane I know that it's 8-bit, so I assume that means a range of 0 to 255 with 128 being the centre line, or something like -128 to 127 with 0 being the centre line if it's signed, right?
That's -128 to 127 with 0 being the centre.

Quote:
 Originally Posted by Foebane I suppose that's only active with a memory location set to 1 or something? (I'm thinking of POKEs) Also, would the 14 bits be represented by the range 0 to 16383 or something similar? It's just that as far as I can see, your description above would favour the top 8 bits over the bottom 6 bits, and so it would be rather skewed. What I mean is, if the memory for the audio was POKEd from 0 to 16383 across 16384 memory registers, would it be a straight line from minimum to maximum?
14 bit is played from 16 bit data. It's a simple table giving the data for each channel.
To make things simple, a data of 1 with a volume of 64 is the same as a data of 64 with a volume of 1 ; therefore a data of 32 with a volume of 1 would be 1/2, and so on down to 1/64.
Normally data from 0 to 16383 should be linear, even though it's not exactly so because of the properties of the D/A (on emulators it is, though).

Quote:
 Originally Posted by Foebane Also, I know that there are volume settings for each channel, and I think a master for all of them, but I figured that they controlled the volume independently of whatever the waveform data was, down to the circuitry of Paula. Are you saying that the volume settings are 100% digital rather than analogue?
Volume settings aren't analogue - the volume is reduced by setting the output level to zero during n/64th of the time (volume 64 is 100%, volume 63 is reduced by 1/64, etc).
The end result is - more or less - like if we had true 14 bit d/a.
There is no master affecting all channels.

I'm perhaps not the best guy to explain all this ; perhaps you could find some docs here and there.

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