Get eighth volume of voice left/right

p1 = voice half-ID

000192b0: 3c028003 lui r2,0x8003
000192b4: 8c42ad44 lw r2,-0x52bc(r2)            # Voice left IO port
000192b8: 00042040 sll r4,r4,0x01  
000192bc: 00822021 addu r4,r4,r2                # voice half-ID port
000192c0: 2402ffff addiu r2,r0,0xffff
000192c4: 94840000 lhu r4,0x0000(r4)            # read volume
000192c8: 10a20005 beq r5,r2,0x000192e0         # end if 0 (return -1)
000192cc: 00000000 nop
000192d0: 3c028003 lui r2,0x8003
000192d4: 8c42ad6c lw r2,-0x5294(r2)            # 3
000192d8: 080064b9 j 0x000192e4                 # return volume / 8
000192dc: 00441004 sllv r2,r4,r2                # volume / 8
000192e0: 00801021 addu r2,r4,r0
000192e4: 03e00008 jr r31
000192e8: 00000000 nop