diff options
author | 2009-09-23 00:30:30 +0000 | |
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committer | 2009-09-23 00:30:30 +0000 | |
commit | 66db5238525fb54b0b058030915f7ad2a38b6046 (patch) | |
tree | 37c76c2fc160408899acbe16e0ae0beb2e97e8f2 /src/emu/sound/disc_dev.c | |
parent | 39bedada9e90469fd98f1cdbe45daace27bd20f0 (diff) |
Optimized DISCRETE_74LS624 making dkongjr and mario faster.
Diffstat (limited to 'src/emu/sound/disc_dev.c')
-rw-r--r-- | src/emu/sound/disc_dev.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/src/emu/sound/disc_dev.c b/src/emu/sound/disc_dev.c index a8a3addfd33..69b3f96e193 100644 --- a/src/emu/sound/disc_dev.c +++ b/src/emu/sound/disc_dev.c @@ -124,6 +124,9 @@ struct dsd_ls624_context int state; double remain; /* remaining time from last step */ int out_type; + double k1; /* precalculated cap part of formula */ + double k2; /* precalculated ring part of formula */ + double k3; /* another precalculated ring part of formula */ }; @@ -1593,8 +1596,12 @@ static DISCRETE_RESET(dsd_566) * where calculated using least square approximation. * This approach gives a bit better results compared to the first approach. */ -#define LS624_F(_C, _VI, _VR) pow(10, -0.912029404 * log10(_C) + 0.243264328 * (_VI) \ +/* Original formula before optimization of static values + #define LS624_F(_C, _VI, _VR) pow(10, -0.912029404 * log10(_C) + 0.243264328 * (_VI) \ - 0.091695877 * (_VR) -0.014110946 * (_VI) * (_VR) - 3.207072925) +*/ +#define LS624_F(_VI) pow(10, context->k1 + 0.243264328 * (_VI) \ + + context->k2 + context->k3 * (_VI)) static DISCRETE_STEP(dsd_ls624) { @@ -1610,7 +1617,7 @@ static DISCRETE_STEP(dsd_ls624) sample_t = node->info->sample_time; /* Change in time */ //dt = LS624_T(DSD_LS624__C, DSD_LS624__VRNG, DSD_LS624__VMOD) / 2.0; - dt = 1.0f / (2.0f * LS624_F(DSD_LS624__C, DSD_LS624__VMOD, DSD_LS624__VRNG)); + dt = 1.0f / (2.0f * LS624_F(DSD_LS624__VMOD)); t = context->remain; en += (double) context->state * t; while (t + dt <= sample_t) @@ -1659,6 +1666,11 @@ static DISCRETE_RESET(dsd_ls624) context->state = 0; context->out_type = DSD_LS624__OUTTYPE; + /* precalculate some parts of the formula for speed */ + context->k1 = -0.912029404 * log10(DSD_LS624__C); + context->k2 = -0.091695877 * (DSD_LS624__VRNG) - 3.207072925; + context->k3 = -0.014110946 * (DSD_LS624__VRNG); + /* Step the output */ DISCRETE_STEP_CALL(dsd_ls624); } |