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Hard limit only if output would clip, and use a table for up to 2x volume level

CQTexperiment
Chris Moeller 2013-10-31 18:20:58 -07:00
parent 355df0b3b0
commit c6529888fd
2 changed files with 30 additions and 9 deletions
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35
Frameworks/GME/gme/Spc_Filter.cpp
View File

@ -22,15 +22,31 @@ static const float limiter_max_05 = (float)(limiter_max - 0.5);
static short hard_limit_sample( int sample ) static short hard_limit_sample( int sample )
{ {
double val = (double)sample * (1.0 / 32768.0); double val = (double)sample * (1.0 / 32768.0);
if (val < -0.5) if (val < -0.5)
val = (tanh((val + 0.5) / limiter_max_05) * limiter_max_05 - 0.5); val = (tanh((val + 0.5) / limiter_max_05) * limiter_max_05 - 0.5);
else if (val > 0.5) else if (val > 0.5)
val = (tanh((val - 0.5) / limiter_max_05) * limiter_max_05 + 0.5); val = (tanh((val - 0.5) / limiter_max_05) * limiter_max_05 + 0.5);
return val * 32768.0; return val * 32768.0;
} }
void Spc_Filter::clear() { memset( ch, 0, sizeof ch ); } void Spc_Filter::build_limit_table()
{
for (int i = -65536; i < 65536; ++i)
{
hard_limit_table[ i + 65536 ] = hard_limit_sample( i );
}
}
inline short Spc_Filter::limit_sample(int sample)
{
if (!limiting && ((unsigned)sample + 32768) < 65536) return sample;
limiting = true;
if (((unsigned)sample + 65536) < 131072) return hard_limit_table[ sample + 65536 ];
return hard_limit_sample( sample );
}
void Spc_Filter::clear() { limiting = false; memset( ch, 0, sizeof ch ); }
Spc_Filter::Spc_Filter() Spc_Filter::Spc_Filter()
{ {
@ -38,6 +54,7 @@ Spc_Filter::Spc_Filter()
gain = gain_unit; gain = gain_unit;
bass = bass_norm; bass = bass_norm;
clear(); clear();
build_limit_table();
} }
void Spc_Filter::run( short io [], int count ) void Spc_Filter::run( short io [], int count )
@ -68,7 +85,7 @@ void Spc_Filter::run( short io [], int count )
int s = sum >> (gain_bits + 2); int s = sum >> (gain_bits + 2);
sum += (delta * gain) - (sum >> bass); sum += (delta * gain) - (sum >> bass);
io [i] = hard_limit_sample( s ); io [i] = limit_sample( s );
} }
c->p1 = p1; c->p1 = p1;
@ -84,7 +101,7 @@ void Spc_Filter::run( short io [], int count )
while ( io < end ) while ( io < end )
{ {
int s = (*io * gain) >> gain_bits; int s = (*io * gain) >> gain_bits;
*io++ = hard_limit_sample( s ); *io++ = limit_sample( s );
} }
} }
} }

4
Frameworks/GME/gme/Spc_Filter.h
View File

@ -40,8 +40,12 @@ private:
int gain; int gain;
int bass; int bass;
bool enabled; bool enabled;
bool limiting;
struct chan_t { int p1, pp1, sum; }; struct chan_t { int p1, pp1, sum; };
chan_t ch [2]; chan_t ch [2];
short hard_limit_table[131072];
void build_limit_table();
inline short limit_sample(int sample);
}; };
inline void Spc_Filter::enable( bool b ) { enabled = b; } inline void Spc_Filter::enable( bool b ) { enabled = b; }