Commit bf66720a4d5feeb1d06dcb1d1a0156ac015bba4b
2022-01-08T12:22:28
fix mixing of U16 audio
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diff --git a/src/audio/SDL_mixer.c b/src/audio/SDL_mixer.c
index 1b55dea..e1f323b 100644
--- a/src/audio/SDL_mixer.c
+++ b/src/audio/SDL_mixer.c
@@ -84,6 +84,7 @@ static const Uint8 mix8[] = {
/* 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)
+#define ADJUST_VOLUME_U16(s, v) (s = (((s-32768)*v)/SDL_MIX_MAXVOLUME)+32768)
void
@@ -190,18 +191,22 @@ SDL_MixAudioFormat(Uint8 * dst, const Uint8 * src, SDL_AudioFormat format,
{
Uint16 src1, src2;
int dst_sample;
- const int max_audioval = SDL_MAX_UINT16;
+ const int max_audioval = SDL_MAX_SINT16;
+ const int min_audioval = SDL_MIN_SINT16;
len /= 2;
while (len--) {
src1 = SDL_SwapLE16(*(Uint16 *)src);
- ADJUST_VOLUME(src1, volume);
+ ADJUST_VOLUME_U16(src1, volume);
src2 = SDL_SwapLE16(*(Uint16 *)dst);
src += 2;
- dst_sample = src1 + src2;
+ dst_sample = src1 + src2 - 32768 * 2;
if (dst_sample > max_audioval) {
dst_sample = max_audioval;
+ } else if (dst_sample < min_audioval) {
+ dst_sample = min_audioval;
}
+ dst_sample += 32768;
*(Uint16 *)dst = SDL_SwapLE16(dst_sample);
dst += 2;
}
@@ -212,18 +217,22 @@ SDL_MixAudioFormat(Uint8 * dst, const Uint8 * src, SDL_AudioFormat format,
{
Uint16 src1, src2;
int dst_sample;
- const int max_audioval = SDL_MAX_UINT16;
+ const int max_audioval = SDL_MAX_SINT16;
+ const int min_audioval = SDL_MIN_SINT16;
len /= 2;
while (len--) {
src1 = SDL_SwapBE16(*(Uint16 *)src);
- ADJUST_VOLUME(src1, volume);
+ ADJUST_VOLUME_U16(src1, volume);
src2 = SDL_SwapBE16(*(Uint16 *)dst);
src += 2;
- dst_sample = src1 + src2;
+ dst_sample = src1 + src2 - 32768 * 2;
if (dst_sample > max_audioval) {
dst_sample = max_audioval;
+ } else if (dst_sample < min_audioval) {
+ dst_sample = min_audioval;
}
+ dst_sample += 32768;
*(Uint16 *)dst = SDL_SwapBE16(dst_sample);
dst += 2;
}