diff options
| -rw-r--r-- | src/chips/opal/opal.c | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/src/chips/opal/opal.c b/src/chips/opal/opal.c index 0cb2c6a..4994e85 100644 --- a/src/chips/opal/opal.c +++ b/src/chips/opal/opal.c @@ -15,8 +15,17 @@ */ #include <stdint.h> +#include <limits.h> #include "opal.h" +#ifndef INT_MAX +# define INT_MAX 2147483647 +#endif + +#ifndef INT_MIN +# define INT_MIN -2147483648 +#endif + /* Various constants */ typedef enum OpalEnumPriv_t { @@ -491,6 +500,23 @@ void Opal_Pan(Opal *self, uint16_t reg_num, uint8_t pan) } +static inline int64_t s_opal_Mul32To64(int32_t a, int32_t b) +{ + return (int64_t)(a) * b; +} + +static inline int32_t s_opal_MulDivR(int32_t a, int32_t b, int32_t c) +{ + int64_t ret = (s_opal_Mul32To64(a, b) + ( c / 2 )) / c; + + if(ret > INT_MAX) + return INT_MAX; + else if(ret < INT_MIN) + return INT_MIN; + else + return (int32_t)(ret); +} + /*================================================================================================== * Generate sample. Every time you call this you will get two signed 16-bit samples (one for each @@ -499,7 +525,7 @@ void Opal_Pan(Opal *self, uint16_t reg_num, uint8_t pan) *=================================================================================================*/ void Opal_Sample(Opal *self, int16_t* left, int16_t* right) { - int32_t omblend; + int32_t fract; /* If the destination sample rate is higher than the OPL3 sample rate, we need to skip ahead */ while(self->SampleAccum >= self->SampleRate) @@ -513,9 +539,9 @@ void Opal_Sample(Opal *self, int16_t* left, int16_t* right) } /* Mix with the partial accumulation */ - omblend = self->SampleRate - self->SampleAccum; - *left = (self->LastOutput[0] * omblend + self->CurrOutput[0] * self->SampleAccum) / self->SampleRate; - *right = (self->LastOutput[1] * omblend + self->CurrOutput[1] * self->SampleAccum) / self->SampleRate; + fract = s_opal_MulDivR(self->SampleAccum, 65536, self->SampleRate); + *left = (int16_t)(self->LastOutput[0] + ((fract * (self->CurrOutput[0] - self->LastOutput[0])) / 65536)); + *right = (int16_t)(self->LastOutput[1] + ((fract * (self->CurrOutput[1] - self->LastOutput[1])) / 65536)); self->SampleAccum += OpalOPL3SampleRate; } |