[hatari-devel] LMC1992 and Microwire emulation

Laurent Sallafranque laurent.sallafranque at free.fr
Mon Mar 8 21:37:28 CET 2010


Hello,

Thanks a lot for the information.
I'll have a look at this at once.

I've committed new volume tables for both Ste DMA sound and Falcon sound.
These tables are logarythmic and are really closer to real hardware 
behaviour.

I've interpolated the 32 elements Yamaha volume table to create a 40 
elements one.
I think my values are really close to real ones.

Regards,

Laurent


David Savinkoff a écrit :
> Hi,
>
> A FFT is not the solution, an IIR filter is required. See:
> http://www.dspguide.com/
> for a freely downloadable book.
> My recommendation is to use a running average filter.
> This is similar to a FIFO, but where you add samples into
> a variable and subtract an old sample out every time you
> add a new one in. How many samples are averaged depends
> on the cut off frequency desired (this is a low pass filter) and
> the sampling frequency. To make a treble filter, subtract an
> averaged value from an input value. Note that the delay of
> the filter is considered to be half of the averaging length.
>
>
> Mar 7, 2010 09:18:03 AM, laurent.sallafranque at free.fr 
> <mailto:laurent.sallafranque at free.fr> 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 ?
>
>     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)
>
>     Do you agree ?
>
>     Could somebody compare volume in protracker in hatari and on a
>     real ste ?
>
>     Regards
>
>     Laurent
>
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