diff options
| author | Chris Robinson <[email protected]> | 2019-08-09 20:09:47 -0700 |
|---|---|---|
| committer | Chris Robinson <[email protected]> | 2019-08-10 14:41:55 -0700 |
| commit | 98029d64b96c2f5edc5dc1e290fa4d30a1338bb4 (patch) | |
| tree | 20af999604ece4f66564a129484a8606931e7c69 /alc/filters | |
| parent | 8f93656f5301b0db1bda15b4c79397f322cf18fe (diff) | |
Fix and clarify the peaking biquad filter
Diffstat (limited to 'alc/filters')
| -rw-r--r-- | alc/filters/biquad.cpp | 1 | ||||
| -rw-r--r-- | alc/filters/biquad.h | 9 |
2 files changed, 5 insertions, 5 deletions
diff --git a/alc/filters/biquad.cpp b/alc/filters/biquad.cpp index 6a3cef64..871c4af4 100644 --- a/alc/filters/biquad.cpp +++ b/alc/filters/biquad.cpp @@ -47,7 +47,6 @@ void BiquadFilterR<Real>::setParams(BiquadType type, Real gain, Real f0norm, Rea a[2] = (gain+1.0f) + (gain-1.0f)*cos_w0 - sqrtgain_alpha_2; break; case BiquadType::Peaking: - gain = std::sqrt(gain); b[0] = 1.0f + alpha * gain; b[1] = -2.0f * cos_w0; b[2] = 1.0f - alpha * gain; diff --git a/alc/filters/biquad.h b/alc/filters/biquad.h index 893a69a9..f8d7f0ba 100644 --- a/alc/filters/biquad.h +++ b/alc/filters/biquad.h @@ -11,10 +11,11 @@ * EQ biquad filter coefficients" by Robert Bristow-Johnson * http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt */ -/* Implementation note: For the shelf filters, the specified gain is for the - * reference frequency, which is the centerpoint of the transition band. This - * better matches EFX filter design. To set the gain for the shelf itself, use - * the square root of the desired linear gain (or halve the dB gain). +/* Implementation note: For the shelf and peaking filters, the specified gain + * is for the centerpoint of the transition band. This better fits EFX filter + * behavior, which expects the shelf's reference frequency to reach the given + * gain. To set the gain for the shelf or peak itself, use the square root of + * the desired linear gain (or halve the dB gain). */ enum class BiquadType { |