diff options
Diffstat (limited to 'audio/softsynth/mt32/DelayReverb.cpp')
| -rw-r--r-- | audio/softsynth/mt32/DelayReverb.cpp | 47 |
1 files changed, 21 insertions, 26 deletions
diff --git a/audio/softsynth/mt32/DelayReverb.cpp b/audio/softsynth/mt32/DelayReverb.cpp index 23d25a596e..77521b4a01 100644 --- a/audio/softsynth/mt32/DelayReverb.cpp +++ b/audio/softsynth/mt32/DelayReverb.cpp @@ -22,7 +22,7 @@ namespace MT32Emu { -// CONFIRMED: The values below are found via analysis of digital samples. Checked with all time and level combinations. +// CONFIRMED: The values below are found via analysis of digital samples and tracing reverb RAM address / data lines. Checked with all time and level combinations. // Obviously: // rightDelay = (leftDelay - 2) * 2 + 2 // echoDelay = rightDelay - 1 @@ -39,10 +39,11 @@ static const Bit32u REVERB_TIMINGS[8][3]= { {8002, 16002, 16001} }; -static const float REVERB_FADE[8] = {0.0f, -0.049400051f, -0.08220577f, -0.131861118f, -0.197344907f, -0.262956344f, -0.345162114f, -0.509508615f}; -const float REVERB_FEEDBACK67 = -0.629960524947437f; // = -EXP2F(-2 / 3) -const float REVERB_FEEDBACK = -0.682034520443118f; // = -EXP2F(-53 / 96) -const float LPF_VALUE = 0.594603558f; // = EXP2F(-0.75f) +// Reverb amp is found as dryAmp * wetAmp +static const Bit32u REVERB_AMP[8] = {0x20*0x18, 0x50*0x18, 0x50*0x28, 0x50*0x40, 0x50*0x60, 0x50*0x80, 0x50*0xA8, 0x50*0xF8}; +static const Bit32u REVERB_FEEDBACK67 = 0x60; +static const Bit32u REVERB_FEEDBACK = 0x68; +static const float LPF_VALUE = 0x68 / 256.0f; DelayReverb::DelayReverb() { buf = NULL; @@ -97,20 +98,18 @@ void DelayReverb::recalcParameters() { // Number of samples between a response and that response feeding back/echoing delayFeedback = REVERB_TIMINGS[time][2] * sampleRate / 32000; - if (time < 6) { - feedback = REVERB_FEEDBACK; + if (level < 3 || time < 6) { + feedback = REVERB_FEEDBACK / 256.0f; } else { - feedback = REVERB_FEEDBACK67; + feedback = REVERB_FEEDBACK67 / 256.0f; } - // Fading speed, i.e. amplitude ratio of neighbor responses - fade = REVERB_FADE[level]; + // Overall output amp + amp = (level == 0 && time == 0) ? 0.0f : REVERB_AMP[level] / 65536.0f; } void DelayReverb::process(const float *inLeft, const float *inRight, float *outLeft, float *outRight, unsigned long numSamples) { - if (buf == NULL) { - return; - } + if (buf == NULL) return; for (unsigned int sampleIx = 0; sampleIx < numSamples; sampleIx++) { // The ring buffer write index moves backwards; reads are all done with positive offsets. @@ -120,10 +119,10 @@ void DelayReverb::process(const float *inLeft, const float *inRight, float *outL Bit32u bufIxFeedback = (bufIx + delayFeedback) % bufSize; // Attenuated input samples and feedback response are directly added to the current ring buffer location - float sample = fade * (inLeft[sampleIx] + inRight[sampleIx]) + feedback * buf[bufIxFeedback]; + float lpfIn = amp * (inLeft[sampleIx] + inRight[sampleIx]) + feedback * buf[bufIxFeedback]; // Single-pole IIR filter found on real devices - buf[bufIx] = buf[bufIxPrev] + (sample - buf[bufIxPrev]) * LPF_VALUE; + buf[bufIx] = buf[bufIxPrev] * LPF_VALUE - lpfIn; outLeft[sampleIx] = buf[bufIxLeft]; outRight[sampleIx] = buf[bufIxRight]; @@ -133,17 +132,13 @@ void DelayReverb::process(const float *inLeft, const float *inRight, float *outL } bool DelayReverb::isActive() const { - // Quick hack: Return true iff all samples in the left buffer are the same and - // all samples in the right buffers are the same (within the sample output threshold). - if (buf == NULL) { - return false; - } - float last = buf[0] * 8192.0f; - for (unsigned int i = 1; i < bufSize; i++) { - float s = (buf[i] * 8192.0f); - if (fabs(s - last) > 1.0f) { - return true; - } + if (buf == NULL) return false; + + float *b = buf; + float max = 0.001f; + for (Bit32u i = 0; i < bufSize; i++) { + if ((*b < -max) || (*b > max)) return true; + b++; } return false; } |