SDL: audio: Generate the channel converter code from a program.

From 49ec8db5f8ba9d386451487bb9e1698ab58346a0 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 19 Jul 2022 22:04:49 -0400
Subject: [PATCH] audio: Generate the channel converter code from a program.

---
 build-scripts/gen_audio_channel_conversion.c |  450 ++++++
 src/audio/SDL_audio_channel_converters.h     | 1459 ++++++++++++++++++
 src/audio/SDL_audiocvt.c                     | 1155 +-------------
 3 files changed, 1911 insertions(+), 1153 deletions(-)
 create mode 100644 build-scripts/gen_audio_channel_conversion.c
 create mode 100644 src/audio/SDL_audio_channel_converters.h

diff --git a/build-scripts/gen_audio_channel_conversion.c b/build-scripts/gen_audio_channel_conversion.c
new file mode 100644
index 00000000000..e74ed2674c4
--- /dev/null
+++ b/build-scripts/gen_audio_channel_conversion.c
@@ -0,0 +1,450 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include <stdio.h>
+
+/*
+
+Built with:
+
+gcc -o genchancvt build-scripts/gen_audio_channel_conversion.c -lm && ./genchancvt > src/audio/SDL_audio_channel_converters.h
+
+*/
+
+#define NUM_CHANNELS 8
+
+static const char *layout_names[NUM_CHANNELS] = {
+    "Mono", "Stereo", "2.1", "Quad", "4.1", "5.1", "6.1", "7.1"
+};
+
+static const char *channel_names[NUM_CHANNELS][NUM_CHANNELS] = {
+    /* mono */   { "FC" },
+    /* stereo */ { "FL", "FR" },
+    /* 2.1 */    { "FL", "FR", "LFE" },
+    /* quad */   { "FL", "FR", "BL", "BR" },
+    /* 4.1 */    { "FL", "FR", "LFE", "BL", "BR" },
+    /* 5.1 */    { "FL", "FR", "FC", "LFE", "BL", "BR" },
+    /* 6.1 */    { "FL", "FR", "FC", "LFE", "BC", "SL", "SR" },
+    /* 7.1 */    { "FL", "FR", "FC", "LFE", "BL", "BR", "SL", "SR" },
+};
+
+
+/*
+ * This table is from FAudio:
+ *
+ *  https://raw.githubusercontent.com/FNA-XNA/FAudio/master/src/matrix_defaults.inl
+ */
+static const float channel_conversion_matrix[8][8][64] = {
+{
+	/* 1 x 1 */
+	{ 1.000000000f },
+	/* 1 x 2 */
+	{ 1.000000000f, 1.000000000f },
+	/* 1 x 3 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f },
+	/* 1 x 4 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f, 0.000000000f },
+	/* 1 x 5 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 1 x 6 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 1 x 7 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 1 x 8 */
+	{ 1.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 2 x 1 */
+	{ 0.500000000f, 0.500000000f },
+	/* 2 x 2 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 2 x 3 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f },
+	/* 2 x 4 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 2 x 5 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 2 x 6 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 2 x 7 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 2 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 3 x 1 */
+	{ 0.333333343f, 0.333333343f, 0.333333343f },
+	/* 3 x 2 */
+	{ 0.800000012f, 0.000000000f, 0.200000003f, 0.000000000f, 0.800000012f, 0.200000003f },
+	/* 3 x 3 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 3 x 4 */
+	{ 0.888888896f, 0.000000000f, 0.111111112f, 0.000000000f, 0.888888896f, 0.111111112f, 0.000000000f, 0.000000000f, 0.111111112f, 0.000000000f, 0.000000000f, 0.111111112f },
+	/* 3 x 5 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 3 x 6 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 3 x 7 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 3 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 4 x 1 */
+	{ 0.250000000f, 0.250000000f, 0.250000000f, 0.250000000f },
+	/* 4 x 2 */
+	{ 0.421000004f, 0.000000000f, 0.358999997f, 0.219999999f, 0.000000000f, 0.421000004f, 0.219999999f, 0.358999997f },
+	/* 4 x 3 */
+	{ 0.421000004f, 0.000000000f, 0.358999997f, 0.219999999f, 0.000000000f, 0.421000004f, 0.219999999f, 0.358999997f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 4 x 4 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 4 x 5 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 4 x 6 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 4 x 7 */
+	{ 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.500000000f, 0.500000000f, 0.000000000f, 0.000000000f, 0.796000004f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.796000004f },
+	/* 4 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 5 x 1 */
+	{ 0.200000003f, 0.200000003f, 0.200000003f, 0.200000003f, 0.200000003f },
+	/* 5 x 2 */
+	{ 0.374222219f, 0.000000000f, 0.111111112f, 0.319111109f, 0.195555553f, 0.000000000f, 0.374222219f, 0.111111112f, 0.195555553f, 0.319111109f },
+	/* 5 x 3 */
+	{ 0.421000004f, 0.000000000f, 0.000000000f, 0.358999997f, 0.219999999f, 0.000000000f, 0.421000004f, 0.000000000f, 0.219999999f, 0.358999997f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f },
+	/* 5 x 4 */
+	{ 0.941176474f, 0.000000000f, 0.058823530f, 0.000000000f, 0.000000000f, 0.000000000f, 0.941176474f, 0.058823530f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.058823530f, 0.941176474f, 0.000000000f, 0.000000000f, 0.000000000f, 0.058823530f, 0.000000000f, 0.941176474f },
+	/* 5 x 5 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 5 x 6 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 5 x 7 */
+	{ 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.500000000f, 0.500000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.796000004f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.796000004f },
+	/* 5 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 6 x 1 */
+	{ 0.166666672f, 0.166666672f, 0.166666672f, 0.166666672f, 0.166666672f, 0.166666672f },
+	/* 6 x 2 */
+	{ 0.294545442f, 0.000000000f, 0.208181813f, 0.090909094f, 0.251818180f, 0.154545456f, 0.000000000f, 0.294545442f, 0.208181813f, 0.090909094f, 0.154545456f, 0.251818180f },
+	/* 6 x 3 */
+	{ 0.324000001f, 0.000000000f, 0.229000002f, 0.000000000f, 0.277000010f, 0.170000002f, 0.000000000f, 0.324000001f, 0.229000002f, 0.000000000f, 0.170000002f, 0.277000010f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f },
+	/* 6 x 4 */
+	{ 0.558095276f, 0.000000000f, 0.394285709f, 0.047619049f, 0.000000000f, 0.000000000f, 0.000000000f, 0.558095276f, 0.394285709f, 0.047619049f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.047619049f, 0.558095276f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.047619049f, 0.000000000f, 0.558095276f },
+	/* 6 x 5 */
+	{ 0.586000025f, 0.000000000f, 0.414000005f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.586000025f, 0.414000005f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.586000025f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.586000025f },
+	/* 6 x 6 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 6 x 7 */
+	{ 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.939999998f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.500000000f, 0.500000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.796000004f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.796000004f },
+	/* 6 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f }
+},
+{
+	/* 7 x 1 */
+	{ 0.143142849f, 0.143142849f, 0.143142849f, 0.142857149f, 0.143142849f, 0.143142849f, 0.143142849f },
+	/* 7 x 2 */
+	{ 0.247384623f, 0.000000000f, 0.174461529f, 0.076923080f, 0.174461529f, 0.226153851f, 0.100615382f, 0.000000000f, 0.247384623f, 0.174461529f, 0.076923080f, 0.174461529f, 0.100615382f, 0.226153851f },
+	/* 7 x 3 */
+	{ 0.268000007f, 0.000000000f, 0.188999996f, 0.000000000f, 0.188999996f, 0.245000005f, 0.108999997f, 0.000000000f, 0.268000007f, 0.188999996f, 0.000000000f, 0.188999996f, 0.108999997f, 0.245000005f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 7 x 4 */
+	{ 0.463679999f, 0.000000000f, 0.327360004f, 0.040000003f, 0.000000000f, 0.168960005f, 0.000000000f, 0.000000000f, 0.463679999f, 0.327360004f, 0.040000003f, 0.000000000f, 0.000000000f, 0.168960005f, 0.000000000f, 0.000000000f, 0.000000000f, 0.040000003f, 0.327360004f, 0.431039989f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.040000003f, 0.327360004f, 0.000000000f, 0.431039989f },
+	/* 7 x 5 */
+	{ 0.483000010f, 0.000000000f, 0.340999991f, 0.000000000f, 0.000000000f, 0.175999999f, 0.000000000f, 0.000000000f, 0.483000010f, 0.340999991f, 0.000000000f, 0.000000000f, 0.000000000f, 0.175999999f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.340999991f, 0.449000001f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.340999991f, 0.000000000f, 0.449000001f },
+	/* 7 x 6 */
+	{ 0.611000001f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.223000005f, 0.000000000f, 0.000000000f, 0.611000001f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.223000005f, 0.000000000f, 0.000000000f, 0.611000001f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.432000011f, 0.568000019f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.432000011f, 0.000000000f, 0.568000019f },
+	/* 7 x 7 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f },
+	/* 7 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.707000017f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.707000017f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f }
+},
+{
+	/* 8 x 1 */
+	{ 0.125125006f, 0.125125006f, 0.125125006f, 0.125000000f, 0.125125006f, 0.125125006f, 0.125125006f, 0.125125006f },
+	/* 8 x 2 */
+	{ 0.211866662f, 0.000000000f, 0.150266662f, 0.066666670f, 0.181066677f, 0.111066669f, 0.194133341f, 0.085866667f, 0.000000000f, 0.211866662f, 0.150266662f, 0.066666670f, 0.111066669f, 0.181066677f, 0.085866667f, 0.194133341f },
+	/* 8 x 3 */
+	{ 0.226999998f, 0.000000000f, 0.160999998f, 0.000000000f, 0.194000006f, 0.119000003f, 0.208000004f, 0.092000000f, 0.000000000f, 0.226999998f, 0.160999998f, 0.000000000f, 0.119000003f, 0.194000006f, 0.092000000f, 0.208000004f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f },
+	/* 8 x 4 */
+	{ 0.466344833f, 0.000000000f, 0.329241365f, 0.034482758f, 0.000000000f, 0.000000000f, 0.169931039f, 0.000000000f, 0.000000000f, 0.466344833f, 0.329241365f, 0.034482758f, 0.000000000f, 0.000000000f, 0.000000000f, 0.169931039f, 0.000000000f, 0.000000000f, 0.000000000f, 0.034482758f, 0.466344833f, 0.000000000f, 0.433517247f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.034482758f, 0.000000000f, 0.466344833f, 0.000000000f, 0.433517247f },
+	/* 8 x 5 */
+	{ 0.483000010f, 0.000000000f, 0.340999991f, 0.000000000f, 0.000000000f, 0.000000000f, 0.175999999f, 0.000000000f, 0.000000000f, 0.483000010f, 0.340999991f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.175999999f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.483000010f, 0.000000000f, 0.449000001f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.483000010f, 0.000000000f, 0.449000001f },
+	/* 8 x 6 */
+	{ 0.518000007f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.188999996f, 0.000000000f, 0.000000000f, 0.518000007f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.188999996f, 0.000000000f, 0.000000000f, 0.518000007f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.518000007f, 0.000000000f, 0.481999993f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.518000007f, 0.000000000f, 0.481999993f },
+	/* 8 x 7 */
+	{ 0.541000009f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.541000009f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.541000009f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.287999988f, 0.287999988f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.458999991f, 0.000000000f, 0.541000009f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.458999991f, 0.000000000f, 0.541000009f },
+	/* 8 x 8 */
+	{ 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 0.000000000f, 1.000000000f }
+}
+};
+
+static char *remove_dots(const char *str)  /* this is NOT robust. */
+{
+    static char retval1[32];
+    static char retval2[32];
+    static int idx = 0;
+    char *retval = (idx++ & 1) ? retval1 : retval2;
+    char *ptr = retval;
+    while (*str) {
+        if (*str != '.') {
+            *(ptr++) = *str;
+        }
+        str++;
+    }
+    *ptr = '\0';
+    return retval;
+}
+
+static char *lowercase(const char *str)  /* this is NOT robust. */
+{
+    static char retval1[32];
+    static char retval2[32];
+    static int idx = 0;
+    char *retval = (idx++ & 1) ? retval1 : retval2;
+    char *ptr = retval;
+    while (*str) {
+        const char ch = *(str++);
+        *(ptr++) = ((ch >= 'A') && (ch <= 'Z')) ? (ch - ('A' - 'a')) : ch;
+    }
+    *ptr = '\0';
+    return retval;
+}
+
+static void write_converter(const int fromchans, const int tochans)
+{
+    const char *fromstr = layout_names[fromchans-1];
+    const char *tostr = layout_names[tochans-1];
+    const float *cvtmatrix = channel_conversion_matrix[fromchans-1][tochans-1];
+    const float *fptr;
+    const int convert_backwards = (tochans > fromchans);
+    int input_channel_used[NUM_CHANNELS];
+    int i, j;
+
+    if (tochans == fromchans) {
+        return;  /* nothing to convert, don't generate a converter. */
+    }
+
+    for (i = 0; i < fromchans; i++) {
+        input_channel_used[i] = 0;
+    }
+
+    fptr = cvtmatrix;
+    for (j = 0; j < tochans; j++) {
+        for (i = 0; i < fromchans; i++) {
+            #if 0
+            printf("to=%d, from=%d, coeff=%f\n", j, i, *fptr);
+            #endif
+            if (*(fptr++) != 0.0f) {
+                input_channel_used[i]++;
+            }
+        }
+    }
+
+    printf("static void SDLCALL\n"
+           "SDL_Convert%sTo%s(SDL_AudioCVT *cvt, SDL_AudioFormat format)\n"
+           "{\n", remove_dots(fromstr), remove_dots(tostr));
+
+    if (convert_backwards) {  /* must convert backwards when growing the output in-place. */
+        printf("    float *dst = ((float *) (cvt->buf + ((cvt->len_cvt / %d) * %d)));\n", fromchans, tochans - 1);
+        printf("    const float *src = ((const float *) (cvt->buf + cvt->len_cvt)) - %d;\n", fromchans);
+    } else {
+        printf("    float *dst = (float *) cvt->buf;\n");
+        printf("    const float *src = dst;\n");
+    }
+
+    printf("    int i;\n"
+           "\n"
+           "    LOG_DEBUG_CONVERT(\"%s\", \"%s\");\n"
+           "    SDL_assert(format == AUDIO_F32SYS);\n"
+           "\n", lowercase(fromstr), lowercase(tostr));
+
+    if (convert_backwards) {
+        printf("    /* convert backwards, since output is growing in-place. */\n");
+        printf("    for (i = cvt->len_cvt / (sizeof (float) * %d); i; i--, src -= %d, dst -= %d) {\n", fromchans, fromchans, tochans);
+        fptr = cvtmatrix;
+        for (i = 0; i < fromchans; i++) {
+            if (input_channel_used[i] > 1) {  /* don't read it from src more than once. */
+                printf("        const float src%s = src[%d];\n", channel_names[fromchans-1][i], i);
+            }
+        }
+
+        for (j = tochans - 1; j >= 0; j--) {
+            int has_input = 0;
+            fptr = cvtmatrix + (fromchans * j);
+            printf("        dst[%d] /* %s */ =", j, channel_names[tochans-1][j]);
+            for (i = fromchans - 1; i >= 0; i--) {
+                const float coefficient = fptr[i];
+                char srcname[32];
+                if (coefficient == 0.0f) {
+                    continue;
+                } else if (input_channel_used[i] > 1) {
+                    snprintf(srcname, sizeof (srcname), "src%s", channel_names[fromchans-1][i]);
+                } else {
+                    snprintf(srcname, sizeof (srcname), "src[%d]", i);
+                }
+
+                if (has_input) {
+                    printf(" +");
+                }
+
+                has_input = 1;
+
+                if (coefficient == 1.0f) {
+                    printf(" %s", srcname);
+                } else {
+                    printf(" (%s * %.9ff)", srcname, coefficient);
+                }
+            }
+
+            if (!has_input) {
+                printf(" 0.0f");
+            }
+
+            printf(";\n");
+        }
+
+        printf("    }\n");
+    } else {
+        printf("    for (i = cvt->len_cvt / (sizeof (float) * %d); i; i--, src += %d, dst += %d) {\n", fromchans, fromchans, tochans);
+
+        fptr = cvtmatrix;
+        for (i = 0; i < fromchans; i++) {
+            if (input_channel_used[i] > 1) {  /* don't read it from src more than once. */
+                printf("        const float src%s = src[%d];\n", channel_names[fromchans-1][i], i);
+            }
+        }
+
+        for (j = 0; j < tochans; j++) {
+            int has_input = 0;
+            fptr = cvtmatrix + (fromchans * j);
+            printf("        dst[%d] /* %s */ =", j, channel_names[tochans-1][j]);
+            for (i = 0; i < fromchans; i++) {
+                const float coefficient = fptr[i];
+                char srcname[32];
+                if (coefficient == 0.0f) {
+                    continue;
+                } else if (input_channel_used[i] > 1) {
+                    snprintf(srcname, sizeof (srcname), "src%s", channel_names[fromchans-1][i]);
+                } else {
+                    snprintf(srcname, sizeof (srcname), "src[%d]", i);
+                }
+
+                if (has_input) {
+                    printf(" +");
+                }
+
+                has_input = 1;
+
+                if (coefficient == 1.0f) {
+                    printf(" %s", srcname);
+                } else {
+                    printf(" (%s * %.9ff)", srcname, coefficient);
+                }
+            }
+
+            if (!has_input) {
+                printf(" 0.0f");
+            }
+
+            printf(";\n");
+        }
+        printf("    }\n");
+    }
+
+    printf("\n");
+
+    if ((fromchans > 1) && (tochans > 1)) {
+        printf("    cvt->len_cvt = (cvt->len_cvt / %d) * %d;\n", fromchans, tochans);
+    } else if (tochans == 1) {
+        printf("    cvt->len_cvt = cvt->len_cvt / %d;\n", fromchans);
+    } else /* if (fromchans == 1) */ {
+        printf("    cvt->len_cvt = cvt->len_cvt * %d;\n", tochans);
+    }
+
+    printf("    if (cvt->filters[++cvt->filter_index]) {\n"
+           "        cvt->filters[cvt->filter_index] (cvt, format);\n"
+           "    }\n"
+           "}\n\n");
+}
+
+int main(void)
+{
+    int ini, outi;
+
+    printf(
+        "/*\n"
+        "  Simple DirectMedia Layer\n"
+        "  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>\n"
+        "\n"
+        "  This software is provided 'as-is', without any express or implied\n"
+        "  warranty.  In no event will the authors be held liable for any damages\n"
+        "  arising from the use of this software.\n"
+        "\n"
+        "  Permission is granted to anyone to use this software for any purpose,\n"
+        "  including commercial applications, and to alter it and redistribute it\n"
+        "  freely, subject to the following restrictions:\n"
+        "\n"
+        "  1. The origin of this software must not be misrepresented; you must not\n"
+        "     claim that you wrote the original software. If you use this software\n"
+        "     in a product, an acknowledgment in the product documentation would be\n"
+        "     appreciated but is not required.\n"
+        "  2. Altered source versions must be plainly marked as such, and must not be\n"
+        "     misrepresented as being the original software.\n"
+        "  3. This notice may not be removed or altered from any source distribution.\n"
+        "*/\n"
+        "\n"
+        "/* DO NOT EDIT, THIS FILE WAS GENERATED BY build-scripts/gen_audio_channel_conversion.c */\n"
+        "\n"
+    );
+
+    for (ini = 1; ini <= NUM_CHANNELS; ini++) {
+        for (outi = 1; outi <= NUM_CHANNELS; outi++) {
+            write_converter(ini, outi);
+        }
+    }
+
+    printf("static const SDL_AudioFilter channel_converters[%d][%d] = {   /* [from][to] */\n", NUM_CHANNELS, NUM_CHANNELS);
+    for (ini = 1; ini <= NUM_CHANNELS; ini++) {
+        const char *comma = "";
+        printf("    {");
+        for (outi = 1; outi <= NUM_CHANNELS; outi++) {
+            const char *fromstr = layout_names[ini-1];
+            const char *tostr = layout_names[outi-1];
+            if (ini == outi) {
+                printf("%s NULL", comma);
+            } else {
+                printf("%s SDL_Convert%sTo%s", comma, remove_dots(fromstr), remove_dots(tostr));
+            }
+            comma = ",";
+        }
+        printf(" }%s\n", (ini == NUM_CHANNELS) ? "" : ",");
+    }
+
+    printf("};\n\n");
+    printf("/* vi: set ts=4 sw=4 expandtab: */\n\n");
+
+    return 0;
+}
+
+/* vi: set ts=4 sw=4 expandtab: */
diff --git a/src/audio/SDL_audio_channel_converters.h b/src/audio/SDL_audio_channel_converters.h
new file mode 100644
index 00000000000..5794a1205c8
--- /dev/null
+++ b/src/audio/SDL_audio_channel_converters.h
@@ -0,0 +1,1459 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this softwa

(Patch may be truncated, please check the link at the top of this post.)