`nx_audio_mix.nx` source

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1// nx_audio_mix.nx -- SOVEREIGN AUDIO ENGINE, rung R0: the PCM mixer atom.
2//
3// Direct answer to "no FMOD/Wwise -- build S-class from the hardware rung up."
4// The core of ANY audio engine (FMOD included) is summing sample streams with
5// per-source gain and clamping to the sample range.  This is that, in raw integer
6// PCM math -- no third party, deterministic, inspectable.  Samples are i64 in the
7// signed-16-bit range; gain is Q8 fixed point (256 = 1.0x).  Later rungs: N-chan,
8// resample, stereo pan, oscillators/ADSR, filters/reverb, 3D spatialization,
9// codecs -- the ladder to EXCEED FMOD (sovereign + no licensing + deterministic).
10// license_tier: ORIGINAL.
11
12import "nx_syscalls.nx"
13
14const AE_GAIN_UNIT: i64 = 256          // Q8 gain: 256 = 1.0x, 128 = 0.5x
15const AE_SMAX: i64 = 32767             // i16 max
16const AE_SMIN: i64 = 0 - 32768         // i16 min
17
18// clamp a mixed sample to the i16 range (prevents wrap/overflow distortion)
19func ae_clamp(x: i64) -> i64 {
20    if x > AE_SMAX { return AE_SMAX }
21    if x < AE_SMIN { return AE_SMIN }
22    return x
23}
24
25// mix two sample buffers with Q8 gains into out[0..n), clamped
26func ae_mix2(a: *i64, b: *i64, ga: i64, gb: i64, out: *i64, n: i64) -> i64 {
27    var i: i64 = 0
28    while i < n {
29        let s: i64 = (a[i] * ga + b[i] * gb) / AE_GAIN_UNIT
30        out[i] = ae_clamp(s)
31        i = i + 1
32    }
33    return n
34}
35
36// mix K sources (srcs[j] = *i64 buffer as i64) with Q8 gains[j] into out[0..n)
37func ae_mixn(srcs: *i64, gains: *i64, k: i64, out: *i64, n: i64) -> i64 {
38    var i: i64 = 0
39    while i < n {
40        var acc: i64 = 0
41        var j: i64 = 0
42        while j < k {
43            let buf: *i64 = srcs[j] as *i64
44            acc = acc + buf[i] * gains[j]
45            j = j + 1
46        }
47        out[i] = ae_clamp(acc / AE_GAIN_UNIT)
48        i = i + 1
49    }
50    return n
51}
52
53// apply a Q8 gain (volume) to a buffer in place, clamped
54func ae_gain(buf: *i64, g: i64, n: i64) -> i64 {
55    var i: i64 = 0
56    while i < n { buf[i] = ae_clamp((buf[i] * g) / AE_GAIN_UNIT); i = i + 1 }
57    return n
58}
nx_audio_mix.nx source

`nx_audio_mix.nx` source
