Mercurial > sdl-ios-xcode
diff src/audio/SDL_audiocvt.c @ 2042:3908e1f808e1
Fixed bug #292
I might be on crack here.
It looks like SDL_ConvertMono() in src/audio/SDL_audiocvt.c adds the left and
right channels of a stereo stream together, and clamps the new mono channel if
it would overflow.
Shouldn't it be dividing by 2 to average the two sample points instead of
clamping? Otherwise the mono sample point's volume doubles in the conversion.
This would also make the conversion faster, as it replaces two branches per
sample frame with a bitwise shift.
--ryan.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 24 Sep 2006 15:56:36 +0000 |
| parents | 7abe37467fa5 |
| children | 5f6550e5184f |
line wrap: on
line diff
--- a/src/audio/SDL_audiocvt.c Sun Sep 24 00:55:19 2006 +0000 +++ b/src/audio/SDL_audiocvt.c Sun Sep 24 15:56:36 2006 +0000 @@ -45,11 +45,7 @@ dst = cvt->buf; for (i = cvt->len_cvt / 2; i; --i) { sample = src[0] + src[1]; - if (sample > 255) { - *dst = 255; - } else { - *dst = (Uint8) sample; - } + *dst = (Uint8) (sample / 2); src += 2; dst += 1; } @@ -64,13 +60,7 @@ dst = (Sint8 *) cvt->buf; for (i = cvt->len_cvt / 2; i; --i) { sample = src[0] + src[1]; - if (sample > 127) { - *dst = 127; - } else if (sample < -128) { - *dst = -128; - } else { - *dst = (Sint8) sample; - } + *dst = (Sint8) (sample / 2); src += 2; dst += 1; } @@ -87,14 +77,10 @@ for (i = cvt->len_cvt / 4; i; --i) { sample = (Uint16) ((src[0] << 8) | src[1]) + (Uint16) ((src[2] << 8) | src[3]); - if (sample > 65535) { - dst[0] = 0xFF; - dst[1] = 0xFF; - } else { - dst[1] = (sample & 0xFF); - sample >>= 8; - dst[0] = (sample & 0xFF); - } + sample /= 2; + dst[1] = (sample & 0xFF); + sample >>= 8; + dst[0] = (sample & 0xFF); src += 4; dst += 2; } @@ -102,14 +88,10 @@ for (i = cvt->len_cvt / 4; i; --i) { sample = (Uint16) ((src[1] << 8) | src[0]) + (Uint16) ((src[3] << 8) | src[2]); - if (sample > 65535) { - dst[0] = 0xFF; - dst[1] = 0xFF; - } else { - dst[0] = (sample & 0xFF); - sample >>= 8; - dst[1] = (sample & 0xFF); - } + sample /= 2; + dst[0] = (sample & 0xFF); + sample >>= 8; + dst[1] = (sample & 0xFF); src += 4; dst += 2; } @@ -127,17 +109,10 @@ for (i = cvt->len_cvt / 4; i; --i) { sample = (Sint16) ((src[0] << 8) | src[1]) + (Sint16) ((src[2] << 8) | src[3]); - if (sample > 32767) { - dst[0] = 0x7F; - dst[1] = 0xFF; - } else if (sample < -32768) { - dst[0] = 0x80; - dst[1] = 0x00; - } else { - dst[1] = (sample & 0xFF); - sample >>= 8; - dst[0] = (sample & 0xFF); - } + sample /= 2; + dst[1] = (sample & 0xFF); + sample >>= 8; + dst[0] = (sample & 0xFF); src += 4; dst += 2; } @@ -145,17 +120,10 @@ for (i = cvt->len_cvt / 4; i; --i) { sample = (Sint16) ((src[1] << 8) | src[0]) + (Sint16) ((src[3] << 8) | src[2]); - if (sample > 32767) { - dst[1] = 0x7F; - dst[0] = 0xFF; - } else if (sample < -32768) { - dst[1] = 0x80; - dst[0] = 0x00; - } else { - dst[0] = (sample & 0xFF); - sample >>= 8; - dst[1] = (sample & 0xFF); - } + sample /= 2; + dst[0] = (sample & 0xFF); + sample >>= 8; + dst[1] = (sample & 0xFF); src += 4; dst += 2; }