Sprinter/mame
2
0
Fork 0
mirror of https://github.com/holub/mame synced 2025-05-25 23:35:26 +03:00
Code Issues Actions Packages Projects Releases Wiki Activity

Fix screeching in regulus: When summing together four equal channels, the size of the max amplitude per channel should be 1/4 of the max range, not 1/3. oops. No idea when this bug is from, but its OLD.

Browse Source
This commit is contained in:
Jonathan Gevaryahu 2009-11-16 05:58:42 +00:00
parent 65dc27ae95
commit a04f60c0f4
1 changed files with 7 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
src/emu/sound/sn76496.c
View File

@ -5,7 +5,7 @@
Routines to emulate the: Routines to emulate the:
Texas Instruments SN76489, SN76489A, SN76494/SN76496 Texas Instruments SN76489, SN76489A, SN76494/SN76496
( Also known as, or at least compatible with, the TMS9919.) ( Also known as, or at least compatible with, the TMS9919 and SN94624.)
and the Sega 'PSG' used on the Master System, Game Gear, and Megadrive/Genesis and the Sega 'PSG' used on the Master System, Game Gear, and Megadrive/Genesis
This chip is known as the Programmable Sound Generator, or PSG, and is a 4 This chip is known as the Programmable Sound Generator, or PSG, and is a 4
channel sound generator, with three squarewave channels and a noise/arbitrary channel sound generator, with three squarewave channels and a noise/arbitrary
@ -48,6 +48,11 @@
14/11/2009 : Lord Nightmare 14/11/2009 : Lord Nightmare
Removed STEP mess, vastly simplifying the code. Made output bipolar rather Removed STEP mess, vastly simplifying the code. Made output bipolar rather
than always above the 0 line, but disabled that code due to pending issues. than always above the 0 line, but disabled that code due to pending issues.
16/11/2009 : Lord Nightmare
Fix screeching in regulus: When summing together four equal channels, the
size of the max amplitude per channel should be 1/4 of the max range, not
1/3.
TODO: * Implement a function for setting stereo regs for the game gear. TODO: * Implement a function for setting stereo regs for the game gear.
Requires making the core support both mono and stereo, and have Requires making the core support both mono and stereo, and have
@ -270,7 +275,7 @@ static void SN76496_set_gain(sn76496_state *R,int gain)
gain &= 0xff; gain &= 0xff;
/* increase max output basing on gain (0.2 dB per step) */ /* increase max output basing on gain (0.2 dB per step) */
out = MAX_OUTPUT / 3; out = MAX_OUTPUT / 4; // four channels, each gets 1/4 of the total range
while (gain-- > 0) while (gain-- > 0)
out *= 1.023292992; /* = (10 ^ (0.2/20)) */ out *= 1.023292992; /* = (10 ^ (0.2/20)) */