Mercurial > sdl-ios-xcode
view src/video/riscos/SDL_riscosASM.S @ 3880:74e828c64315 SDL-1.2
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 15:45:37 +0000 |
parents | 1e8582152d44 |
children | 99210400e8b9 |
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; ; SDL - Simple DirectMedia Layer ; Copyright (C) 1997-2004 Sam Lantinga ; ; This library is free software; you can redistribute it and/or ; modify it under the terms of the GNU Library General Public ; License as published by the Free Software Foundation; either ; version 2 of the License, or (at your option) any later version. ; ; This library is distributed in the hope that it will be useful, ; but WITHOUT ANY WARRANTY; without even the implied warranty of ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ; Library General Public License for more details. ; ; You should have received a copy of the GNU Library General Public ; License along with this library; if not, write to the Free ; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ; ; Sam Lantinga ; slouken@libsdl.org ; ; Assembler routines for RISC OS display ; AREA |C$$CODE| EXPORT |RISCOS_Put32| ; Display 32bpp to 32bpp, 1:1 ; ; Code provided by Adrain Lees ; ; entry a1 -> destination ; a2 = dest width in pixels ; a3 = dest line length in bytes ; a4 = dest height in scanlines ; arg5 -> source ; arg6 = byte offset from end of source line to start of next Arg5 * 10*4 Arg6 * Arg5+4 RISCOS_Put32 ROUT STMFD sp!,{a2,v1-v6,sl,fp,lr} LDR ip,[sp,#Arg5] MOV lr,a1 B ucp64lp 00 ;tail strip of 1-15 pixels LDR v1,[ip],#4 01 SUBS a2,a2,#1 STR v1,[lr],#4 LDRHI v1,[ip],#4 BHI %01 B %02 ucp64end ADDS a2,a2,#16 BNE %00 02 SUBS a4,a4,#1 ;height-- LDRHI v1,[sp,#Arg6] LDRHI a2,[sp] ;reload width BLS %03 ;move to start of next scanline ADD lr,a1,a3 ADD a1,a1,a3 ADD ip,ip,v1 ucp64lp SUBS a2,a2,#16 BLO ucp64end PLD [ip,#64] LDR v1,[ip],#4 LDR v2,[ip],#4 LDR v3,[ip],#4 LDR v4,[ip],#4 LDR v5,[ip],#4 LDR v6,[ip],#4 LDR sl,[ip],#4 LDR fp,[ip],#4 STR v1,[lr],#4 STR v2,[lr],#4 STR v3,[lr],#4 STR v4,[lr],#4 STR v5,[lr],#4 STR v6,[lr],#4 STR sl,[lr],#4 STR fp,[lr],#4 PLD [ip,#64] LDR v1,[ip],#4 LDR v2,[ip],#4 LDR v3,[ip],#4 LDR v4,[ip],#4 LDR v5,[ip],#4 LDR v6,[ip],#4 LDR sl,[ip],#4 LDR fp,[ip],#4 STR v1,[lr],#4 STR v2,[lr],#4 STR v3,[lr],#4 STR v4,[lr],#4 STR v5,[lr],#4 STR v6,[lr],#4 STR sl,[lr],#4 STR fp,[lr],#4 B ucp64lp 03 LDMFD sp!,{a2,v1-v6,sl,fp,pc}