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Corrected the 202 entry in the LFO Frequency Table (and comments for it) for the YMF271 based on a formula by Olivier Galibert. (Brian Troha, Roman Scherzer)

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Brian Troha 2009-05-19 01:37:45 +00:00
parent c4b557d602
commit 90d2e8e705
1 changed files with 20 additions and 3 deletions
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23
src/emu/sound/ymf271.c
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@ -162,8 +162,25 @@ static const double DCTime[] =
There appears to be at least 2 errors in the table from the original manual.
Both 201 & 202 where listed as 3.74490. 202 has be changed to 3.92000 which is "about right"
232 was listed as 13.35547. We use 14.35547 as it apears to be the correct value
Both 201 & 202 where listed as 3.74490. 202 has be changed to 3.91513 which was computed based on formulas by OG & Nicola
232 was listed as 13.35547. We use 14.35547 as this is the correct value based on the formula listed below:
LFO period seems easy to compute:
int lfo_period(int entry)
{
int ma, ex;
entry = 256-entry;
ma = entry & 15;
ex = entry >> 4;
if(ex)
return (ma | 16) << (ex+6);
else
return ma << 7;
}
lfo_freq = 44100 / lfo_period
*/
static const double LFO_frequency_table[256] =
@ -193,7 +210,7 @@ static const double LFO_frequency_table[256] =
1.34583, 1.38924, 1.43555, 1.48505, 1.53809, 1.59509, 1.65640, 1.72266,
1.79443, 1.87245, 1.95756, 2.05078, 2.15332, 2.26665, 2.39258, 2.53332,
2.69165, 2.77848, 2.87109, 2.97010, 3.07617, 3.19010, 3.31280, 3.44531,
3.58887, 3.74490, 3.92000, 4.10156, 4.30664, 4.53331, 4.78516, 5.06664,
3.58887, 3.74490, 3.91513, 4.10156, 4.30664, 4.53331, 4.78516, 5.06664,
5.38330, 5.55696, 5.74219, 5.94019, 6.15234, 6.38021, 6.62560, 6.89062,
7.17773, 7.48981, 7.83026, 8.20312, 8.61328, 9.06661, 9.57031, 10.13327,
10.76660, 11.11391, 11.48438, 11.88039, 12.30469, 12.76042, 13.25120, 13.78125,