AuroraMiddleware/AuroraOpenALSoft
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Update a couple comments about the reverb modulation

Browse Source
This commit is contained in:
Chris Robinson 2017-05-13 16:08:45 -07:00
parent 0b66b2bbe7
commit 7cbce6806b
1 changed files with 13 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
Alc/effects/reverb.c
View File

@ -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;