duke3d: further optimize audio mixing

Rather than holding intermediate results as fixed-point, this converts them
directly to normal integers (in the range of the PCM sample) while mixing,
instead of waiting till the end to perform a separate shifting step. Also,
this precalculates some constants in the reverb code.

Change-Id: Ie04e444d145bc28ce67eef9ae0ead6d328acf28a

1 files changed, 7 insertions, 3 deletions

diff --git a/apps/plugins/sdl/progs/duke3d/Engine/src/display.c b/apps/plugins/sdl/progs/duke3d/Engine/src/display.c
index 3883803bce..501ffa411c 100644
--- a/apps/plugins/sdl/progs/duke3d/Engine/src/display.c
+++ b/apps/plugins/sdl/progs/duke3d/Engine/src/display.c
@@ -1368,9 +1368,13 @@ int VBE_setPalette(uint8_t  *palettebuffer)
     memcpy(lastPalette, palettebuffer, 768);
     
     for (i = 0; i < 256; i++){
-        sdlp->b = (Uint8) ((((float) *p++) / 63.0) * 255.0);
-        sdlp->g = (Uint8) ((((float) *p++) / 63.0) * 255.0);
-        sdlp->r = (Uint8) ((((float) *p++) / 63.0) * 255.0);
+        /* doesn't map perfectly */
+        sdlp->b = (Uint8) (*p << 2) | (*p >> 4);
+        p++;
+        sdlp->g = (Uint8) (*p << 2) | (*p >> 4);
+        p++;
+        sdlp->r = (Uint8) (*p << 2) | (*p >> 4);
+        p++;
         sdlp->unused = *p++;   /* This byte is unused in BUILD, too. */
         sdlp++;
     }