1 @*********************************************************** 2 @ Function: SynthMasterGain 3 @ Processor: ARM-E 4 @ Description: Copies 32-bit synth output to 16-bit buffer 5 @ with saturated gain control 6 @ C-callable. 7 @ 8 @ Usage: 9 @ SynthMasterGain( 10 @ pInputBuffer 11 @ pOutputBuffer, 12 @ nGain, 13 @ nNumLoopSamples 14 @ ); 15 @ 16 @ Copyright Sonic Network Inc. 2004 17 @**************************************************************** 18 @ Revision Control: 19 @ $Revision: 496 $ 20 @ $Date: 2006-12-11 14:33:26 -0800 (Mon, 11 Dec 2006) $ 21 @**************************************************************** 22 @ 23 @ where: 24 @ long *pInputBuffer 25 @ PASSED IN: r0 26 @ 27 @ EAS_PCM *pOutputBuffer 28 @ PASSED IN: r1 29 @ 30 @ short nGain 31 @ PASSED IN: r2 32 @ 33 @ EAS_U16 nNumLoopSamples 34 @ PASSED IN: r3 35 @ 36 @**************************************************************** 37 38 #include "ARM_synth_constants_gnu.inc" 39 40 .arm 41 .text 42 43 .func SynthMasterGain 44 SynthMasterGain: 45 46 .global SynthMasterGain @ allow other files to use this function 47 48 49 50 51 52 @ Stack frame 53 @ ----------- 54 .equ RET_ADDR_SZ, 0 @return address 55 .equ REG_SAVE_SZ, 0 @save-on-entry registers saved 56 .equ FRAME_SZ, (8) @local variables 57 .equ ARG_BLK_SZ, 0 @argument block 58 59 .equ PARAM_OFFSET, (ARG_BLK_SZ + FRAME_SZ + REG_SAVE_SZ + RET_ADDR_SZ) 60 61 @ Register usage 62 @ -------------- 63 pnInputBuffer .req r0 64 pnOutputBuffer .req r1 65 nGain .req r2 66 nNumLoopSamples .req r3 67 68 STMFD sp!,{r4-r6,r14} @Save any save-on-entry registers that are used 69 70 LDR r6, =0x7fff @constant for saturation tests 71 72 loop: 73 LDR r4, [pnInputBuffer], #4 @fetch 1st output sample 74 75 LDR r5, [pnInputBuffer], #4 @fetch 2nd output sample 76 77 SMULWB r4, r4, nGain @output = gain * input 78 79 CMP r4, r6 @check for positive saturation 80 MOVGT r4, r6 @saturate 81 CMN r4, r6 @check for negative saturation 82 MVNLT r4, r6 @saturate 83 84 SMULWB r5, r5, nGain @output = gain * input 85 86 STRH r4, [pnOutputBuffer], #NEXT_OUTPUT_PCM @save 1st output sample 87 88 CMP r5, r6 @check for positive saturation 89 MOVGT r5, r6 @saturate 90 CMN r5, r6 @check for negative saturation 91 MVNLT r5, r6 @saturate 92 STRH r5, [pnOutputBuffer], #NEXT_OUTPUT_PCM @save 2nd output sample 93 94 SUBS nNumLoopSamples, nNumLoopSamples, #2 95 BGT loop 96 97 @ 98 @ Return to calling function 99 @---------------------------------------------------------------- 100 101 LDMFD sp!,{r4-r6, lr} @ return to calling function 102 BX lr 103 104 @***************************************************************************** 105 106 .endfunc @ end of function/procedure 107 108 .end @ end of assembly code 109 110
