[hatari-devel] LMC1992 and Microwire emulation

Laurent Sallafranque laurent.sallafranque at free.fr
Sun Mar 7 21:37:33 CET 2010


I totally agree with you.

The main problem is that I've only got a 520 STf.

Another point, if we want to be accurate is the 8 cpu cycles interrupt 
for the Microwire.
If a 68000 instruction takes 50 cycles (for examples), we should detect 
this and rotate the microwire mask 6 times instead of only one.

Nicolas, you know how to do this better than me, could you add this 
feature ?

I'll try to have a look at the bass and treble algos during this time.

Regards,

Laurent




npomarede at corp.free.fr a écrit :
> On Sun, 7 Mar 2010, Laurent Sallafranque wrote:
>
>> Hello,
>>
>> I've added LMC1992 and Microwire emulation to hatari.
>>
>> For now, Master volume, left volume and right volume are emulated.
>> Still to do : Bass and Treble.
>> Does it need a FFT and FFT -1 transformation or are there specifics 
>> algorythms for bass and treble ?
>
> Hello,
>
> I think we can find some pointers for this on the web, but this 
> certainly requires more computations than a simple filter (fft or 
> maybe some specific faster method ?)
>
>>
>> I've done my tests with protracker Ste.
>>
>> I think there's a problem anyway for both falcon volume table and ste 
>> volume table :
>>
>> I've used a linear volume table to calculate values from the min to 
>> the max.
>> I think values should be calculated with a logarythmic algo.
>> (There's only values in the volume_table to change, nothing else)
>
> for the ym2149, volume is clerly not linear and the table is 
> logarithmic, maybe you can use it as a starting point (there're only 
> 16 values, but you can deduce a similar table for 256 values)
>
>> Do you agree ?
>>
>> Could somebody compare volume in protracker in hatari and on a real 
>> ste ?
>
> The real solution would be to play a constant sample sound (square 
> wave consisting of values 127 and -127) at 50 kHz and then measure the 
> output voltage on the audio out pin of the ste for example. By doing 
> measures for 32 different volumes or so between 0 and max, this should 
> give the correct graph to extrapolate all values (that's the method 
> used to get the 16 volumes level of the ym2149)
>
> Nicolas
>
>
>




More information about the hatari-devel mailing list