1/*
2Copyright 2018 Google Inc. All Rights Reserved.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS-IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17#ifndef RESONANCE_AUDIO_DSP_DISTANCE_ATTENUATION_H_
18#define RESONANCE_AUDIO_DSP_DISTANCE_ATTENUATION_H_
19
20#include "base/misc_math.h"
21#include "base/source_parameters.h"
22
23namespace vraudio {
24
25// Returns the distance attenuation for |source_position| with respect to
26// |listener_position|. The amplitude will decrease by approximately 6 dB every
27// time the distance is doubled, i.e., the sound pressure "p" (amplitude)
28// approximately falls inversely proportional to the distance "1/r".
29//
30// @param listener_position World position of the listener.
31// @param source_position World position of the source.
32// @param min_distance The minimum distance at which distance attenuation is
33// applied.
34// @param max_distance The maximum distance at which the direct sound has a gain
35// of 0.0.
36// @return Attenuation (gain) value in range [0.0f, 1.0f].
37float ComputeLogarithmicDistanceAttenuation(
38 const WorldPosition& listener_position,
39 const WorldPosition& source_position, float min_distance,
40 float max_distance);
41
42// Returns the distance attenuation for |source_position| with respect to
43// |listener_position|. The amplitude will decrease linearly between
44// |min_distance| and |max_distance| from 1.0 to 0.0.
45//
46// @param listener_position World position of the listener.
47// @param source_position World position of the source.
48// @param min_distance The minimum distance at which distance attenuation is
49// applied.
50// @param max_distance The maximum distance at which the direct sound has a gain
51// of 0.0.
52// @return Attenuation (gain) value in range [0.0f, 1.0f].
53float ComputeLinearDistanceAttenuation(const WorldPosition& listener_position,
54 const WorldPosition& source_position,
55 float min_distance, float max_distance);
56
57// Calculates the gain to be applied to the near field compensating stereo mix.
58// This function will return 0.0f for all sources further away than one meter
59// and will return a value between 0.0 and 9.0 for sources as they approach
60// the listener's head location.
61//
62// @param listener_position World position of the listener.
63// @param source_position World position of the source.
64// @return Gain value in range [0.0f, 9.0f].
65float ComputeNearFieldEffectGain(const WorldPosition& listener_position,
66 const WorldPosition& source_position);
67
68// Calculates and updates gain attenuations of the given source |parameters|.
69//
70// @param master_gain Global gain adjustment in amplitude.
71// @param reflections_gain Reflections gain in amplitude.
72// @param reverb_gain Reverb gain in amplitude.
73// @param listener_position World position of the listener.
74// @param parameters Source parameters to apply the gain attenuations into.
75void UpdateAttenuationParameters(float master_gain, float reflections_gain,
76 float reverb_gain,
77 const WorldPosition& listener_position,
78 SourceParameters* parameters);
79
80} // namespace vraudio
81
82#endif // RESONANCE_AUDIO_DSP_DISTANCE_ATTENUATION_H_
83

source code of qtmultimedia/src/3rdparty/resonance-audio/resonance_audio/dsp/distance_attenuation.h