src/audio/SDL_mixer.c
author Ryan C. Gordon <icculus@icculus.org>
Sun, 28 Aug 2016 13:36:13 -0400
changeset 10286 3b884985835c
parent 9998 f67cf37e9cd4
permissions -rw-r--r--
Merge audio capture work back into the mainline.

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2016 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 "../SDL_internal.h"

/* This provides the default mixing callback for the SDL audio routines */

#include "SDL_cpuinfo.h"
#include "SDL_timer.h"
#include "SDL_audio.h"
#include "SDL_sysaudio.h"

/* This table is used to add two sound values together and pin
 * the value to avoid overflow.  (used with permission from ARDI)
 * Changed to use 0xFE instead of 0xFF for better sound quality.
 */
static const Uint8 mix8[] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03,
    0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
    0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24,
    0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A,
    0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45,
    0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50,
    0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x5B,
    0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66,
    0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71,
    0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C,
    0x7D, 0x7E, 0x7F, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
    0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F, 0x90, 0x91, 0x92,
    0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D,
    0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8,
    0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3,
    0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE,
    0xBF, 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9,
    0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF, 0xD0, 0xD1, 0xD2, 0xD3, 0xD4,
    0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF,
    0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA,
    0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5,
    0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
    0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE
};

/* The volume ranges from 0 - 128 */
#define ADJUST_VOLUME(s, v) (s = (s*v)/SDL_MIX_MAXVOLUME)
#define ADJUST_VOLUME_U8(s, v)  (s = (((s-128)*v)/SDL_MIX_MAXVOLUME)+128)


void
SDL_MixAudioFormat(Uint8 * dst, const Uint8 * src, SDL_AudioFormat format,
                   Uint32 len, int volume)
{
    if (volume == 0) {
        return;
    }

    switch (format) {

    case AUDIO_U8:
        {
#if defined(__GNUC__) && defined(__M68000__) && !defined(__mcoldfire__) && defined(SDL_ASSEMBLY_ROUTINES)
            SDL_MixAudio_m68k_U8((char *) dst, (char *) src,
                                 (unsigned long) len, (long) volume,
                                 (char *) mix8);
#else
            Uint8 src_sample;

            while (len--) {
                src_sample = *src;
                ADJUST_VOLUME_U8(src_sample, volume);
                *dst = mix8[*dst + src_sample];
                ++dst;
                ++src;
            }
#endif
        }
        break;

    case AUDIO_S8:
        {
            Sint8 *dst8, *src8;
            Sint8 src_sample;
            int dst_sample;
            const int max_audioval = ((1 << (8 - 1)) - 1);
            const int min_audioval = -(1 << (8 - 1));

            src8 = (Sint8 *) src;
            dst8 = (Sint8 *) dst;
            while (len--) {
                src_sample = *src8;
                ADJUST_VOLUME(src_sample, volume);
                dst_sample = *dst8 + src_sample;
                if (dst_sample > max_audioval) {
                    *dst8 = max_audioval;
                } else if (dst_sample < min_audioval) {
                    *dst8 = min_audioval;
                } else {
                    *dst8 = dst_sample;
                }
                ++dst8;
                ++src8;
            }
        }
        break;

    case AUDIO_S16LSB:
        {
            Sint16 src1, src2;
            int dst_sample;
            const int max_audioval = ((1 << (16 - 1)) - 1);
            const int min_audioval = -(1 << (16 - 1));

            len /= 2;
            while (len--) {
                src1 = ((src[1]) << 8 | src[0]);
                ADJUST_VOLUME(src1, volume);
                src2 = ((dst[1]) << 8 | dst[0]);
                src += 2;
                dst_sample = src1 + src2;
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                dst[0] = dst_sample & 0xFF;
                dst_sample >>= 8;
                dst[1] = dst_sample & 0xFF;
                dst += 2;
            }
        }
        break;

    case AUDIO_S16MSB:
        {
#if defined(__GNUC__) && defined(__M68000__) && !defined(__mcoldfire__) && defined(SDL_ASSEMBLY_ROUTINES)
            SDL_MixAudio_m68k_S16MSB((short *) dst, (short *) src,
                                     (unsigned long) len, (long) volume);
#else
            Sint16 src1, src2;
            int dst_sample;
            const int max_audioval = ((1 << (16 - 1)) - 1);
            const int min_audioval = -(1 << (16 - 1));

            len /= 2;
            while (len--) {
                src1 = ((src[0]) << 8 | src[1]);
                ADJUST_VOLUME(src1, volume);
                src2 = ((dst[0]) << 8 | dst[1]);
                src += 2;
                dst_sample = src1 + src2;
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                dst[1] = dst_sample & 0xFF;
                dst_sample >>= 8;
                dst[0] = dst_sample & 0xFF;
                dst += 2;
            }
#endif
        }
        break;

    case AUDIO_S32LSB:
        {
            const Uint32 *src32 = (Uint32 *) src;
            Uint32 *dst32 = (Uint32 *) dst;
            Sint64 src1, src2;
            Sint64 dst_sample;
            const Sint64 max_audioval = ((((Sint64) 1) << (32 - 1)) - 1);
            const Sint64 min_audioval = -(((Sint64) 1) << (32 - 1));

            len /= 4;
            while (len--) {
                src1 = (Sint64) ((Sint32) SDL_SwapLE32(*src32));
                src32++;
                ADJUST_VOLUME(src1, volume);
                src2 = (Sint64) ((Sint32) SDL_SwapLE32(*dst32));
                dst_sample = src1 + src2;
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                *(dst32++) = SDL_SwapLE32((Uint32) ((Sint32) dst_sample));
            }
        }
        break;

    case AUDIO_S32MSB:
        {
            const Uint32 *src32 = (Uint32 *) src;
            Uint32 *dst32 = (Uint32 *) dst;
            Sint64 src1, src2;
            Sint64 dst_sample;
            const Sint64 max_audioval = ((((Sint64) 1) << (32 - 1)) - 1);
            const Sint64 min_audioval = -(((Sint64) 1) << (32 - 1));

            len /= 4;
            while (len--) {
                src1 = (Sint64) ((Sint32) SDL_SwapBE32(*src32));
                src32++;
                ADJUST_VOLUME(src1, volume);
                src2 = (Sint64) ((Sint32) SDL_SwapBE32(*dst32));
                dst_sample = src1 + src2;
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                *(dst32++) = SDL_SwapBE32((Uint32) ((Sint32) dst_sample));
            }
        }
        break;

    case AUDIO_F32LSB:
        {
            const float fmaxvolume = 1.0f / ((float) SDL_MIX_MAXVOLUME);
            const float fvolume = (float) volume;
            const float *src32 = (float *) src;
            float *dst32 = (float *) dst;
            float src1, src2;
            double dst_sample;
            /* !!! FIXME: are these right? */
            const double max_audioval = 3.402823466e+38F;
            const double min_audioval = -3.402823466e+38F;

            len /= 4;
            while (len--) {
                src1 = ((SDL_SwapFloatLE(*src32) * fvolume) * fmaxvolume);
                src2 = SDL_SwapFloatLE(*dst32);
                src32++;

                dst_sample = ((double) src1) + ((double) src2);
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                *(dst32++) = SDL_SwapFloatLE((float) dst_sample);
            }
        }
        break;

    case AUDIO_F32MSB:
        {
            const float fmaxvolume = 1.0f / ((float) SDL_MIX_MAXVOLUME);
            const float fvolume = (float) volume;
            const float *src32 = (float *) src;
            float *dst32 = (float *) dst;
            float src1, src2;
            double dst_sample;
            /* !!! FIXME: are these right? */
            const double max_audioval = 3.402823466e+38F;
            const double min_audioval = -3.402823466e+38F;

            len /= 4;
            while (len--) {
                src1 = ((SDL_SwapFloatBE(*src32) * fvolume) * fmaxvolume);
                src2 = SDL_SwapFloatBE(*dst32);
                src32++;

                dst_sample = ((double) src1) + ((double) src2);
                if (dst_sample > max_audioval) {
                    dst_sample = max_audioval;
                } else if (dst_sample < min_audioval) {
                    dst_sample = min_audioval;
                }
                *(dst32++) = SDL_SwapFloatBE((float) dst_sample);
            }
        }
        break;

    default:                   /* If this happens... FIXME! */
        SDL_SetError("SDL_MixAudio(): unknown audio format");
        return;
    }
}

/* vi: set ts=4 sw=4 expandtab: */