SDL/build-scripts/gen_audio_channel_conversion.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2025 Sam Lantinga <[email protected]>

  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))) - %d;\n", fromchans, tochans, tochans);
        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) 1997-2025 Sam Lantinga <[email protected]>\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: */