diff options
| -rw-r--r-- | Alc/effects/reverb.c | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/Alc/effects/reverb.c b/Alc/effects/reverb.c index 92698bd4..f00ee624 100644 --- a/Alc/effects/reverb.c +++ b/Alc/effects/reverb.c @@ -1055,24 +1055,25 @@ static ALvoid UpdateModulator(const ALfloat modTime, const ALfloat modDepth, /* Modulation is calculated in two parts. * - * The modulation time effects the sinus applied to the change in - * frequency. An index out of the current time range (both in samples) - * is incremented each sample. The range is bound to a reasonable - * minimum (1 sample) and when the timing changes, the index is rescaled - * to the new range (to keep the sinus consistent). + * The modulation time effects the speed of the sinus. An index out of the + * current range (both in samples) is incremented each sample, so a longer + * time implies a larger range. The range is bound to a reasonable minimum + * (1 sample) and when the timing changes, the index is rescaled to the new + * range to keep the sinus consistent. */ range = maxu(fastf2u(modTime*frequency), 1); State->Mod.Index = (ALuint)(State->Mod.Index * (ALuint64)range / State->Mod.Range); State->Mod.Range = range; - /* The modulation depth effects the amount of frequency change over the - * range of the sinus. It needs to be scaled by the modulation time so - * that a given depth produces a consistent change in frequency over all - * ranges of time. Since the depth is applied to a sinus value, it needs - * to be halfed once for the sinus range and again for the sinus swing - * in time (half of it is spent decreasing the frequency, half is spent - * increasing it). + /* The modulation depth effects the scale of the sinus, which changes how + * much extra delay is added to the delay line. This delay changing over + * time changes the pitch, creating the modulation effect. The scale needs + * to be multiplied by the modulation time so that a given depth produces a + * consistent shift in frequency over all ranges of time. Since the depth + * is applied to a sinus value, it needs to be halved once for the sinus + * range (-1...+1 to 0...1) and again for the sinus swing in time (half of + * it is spent decreasing the frequency, half is spent increasing it). */ State->Mod.Depth = modDepth * MODULATION_DEPTH_COEFF * modTime / 2.0f / 2.0f * frequency; |