134 lines
3.7 KiB
ArmAsm
134 lines
3.7 KiB
ArmAsm
@***********************************************************
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@ Function: WT_Interpolate
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@ Processor: ARM-E
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@ Description: the main synthesis function when fetching
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@ wavetable samples.
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@ C-callable.
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@
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@ Usage:
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@ void WT_Interpolate(
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@ S_WT_VOICE *pWTVoice,
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@ S_WT_FRAME *pWTFrame);
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@
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@ Copyright Sonic Network Inc. 2004
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@****************************************************************
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@ Revision Control:
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@ $Revision: 496 $
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@ $Date: 2006-12-11 14:33:26 -0800 (Mon, 11 Dec 2006) $
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@****************************************************************
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@
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@ where:
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@ S_WT_VOICE *pWTVoice
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@ PASSED IN: r0
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@
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@ S_WT_FRAME *pWTFrame;
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@ PASSED IN: r1
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@****************************************************************
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#include "ARM_synth_constants_gnu.inc"
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.arm
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.text
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.global WT_Interpolate
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@ Register usage
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@ --------------
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pWTVoice .req r0
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pWTFrame .req r1
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numSamples .req r2
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phaseIncrement .req r3
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pOutputBuffer .req r4
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tmp0 .req r1 @reuse register
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tmp1 .req r5
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tmp2 .req r6
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pLoopEnd .req r7
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pLoopStart .req r8
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pPhaseAccum .req r9
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phaseFrac .req r10
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phaseFracMask .req r11
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@SaveRegs RLIST {r4-r11,lr}
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@RestoreRegs RLIST {r4-r11,pc}
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WT_Interpolate:
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STMFD sp!,{r4-r11,lr}
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@
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@ Fetch parameters from structures
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@----------------------------------------------------------------
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LDR pOutputBuffer, [pWTFrame, #m_pAudioBuffer]
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LDR numSamples, [pWTFrame, #m_numSamples]
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LDR phaseIncrement, [pWTFrame, #m_phaseIncrement]
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LDR pPhaseAccum, [pWTVoice, #m_pPhaseAccum]
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LDR phaseFrac, [pWTVoice, #m_phaseFrac]
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LDR phaseFracMask,=PHASE_FRAC_MASK
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LDR pLoopStart, [pWTVoice, #m_pLoopStart]
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LDR pLoopEnd, [pWTVoice, #m_pLoopEnd]
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ADD pLoopEnd, pLoopEnd, #1 @ need loop end to equal last sample + 1
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InterpolationLoop:
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SUBS tmp0, pPhaseAccum, pLoopEnd @ check for loop end
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ADDGE pPhaseAccum, pLoopStart, tmp0 @ loop back to start
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#ifdef SAMPLES_8_BIT
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LDRSB tmp0, [pPhaseAccum] @ tmp0 = x0
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LDRSB tmp1, [pPhaseAccum, #1] @ tmp1 = x1
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#elif SAMPLES_16_BIT
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LDRSH tmp0, [pPhaseAccum] @ tmp0 = x0
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LDRSH tmp1, [pPhaseAccum, #2] @ tmp1 = x1
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#else
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#error Must define one of SAMPLES_8_BIT or SAMPLES_16_BIT.
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#endif
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ADD tmp2, phaseIncrement, phaseFrac @ increment pointer here to avoid pipeline stall
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SUB tmp1, tmp1, tmp0 @ tmp1 = x1 - x0
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SMULBB tmp1, phaseFrac, tmp1 @ tmp1 = phaseFrac * tmp2
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@ This section performs a gain adjustment of -12dB for 16-bit samples
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@ or +36dB for 8-bit samples. For a high quality synthesizer, the output
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@ can be set to full scale, however if the filter is used, it can overflow
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@ with certain coefficients and signal sources. In this case, either a
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@ saturation operation should take in the filter before scaling back to
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@ 16 bits or the signal path should be increased to 18 bits or more.
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#ifdef SAMPLES_8_BIT
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MOV tmp0, tmp0, LSL #6 @ boost 8-bit signal by 36dB
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#elif SAMPLES_16_BIT
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MOV tmp0, tmp0, ASR #2 @ reduce 16-bit signal by 12dB
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#else
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#error Must define one of SAMPLES_8_BIT or SAMPLES_16_BIT.
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#endif
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ADD tmp1, tmp0, tmp1, ASR #(NUM_EG1_FRAC_BITS-6) @ tmp1 = tmp0 + (tmp1 >> (15-6))
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@ = x0 + f * (x1 - x0) == interpolated result
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STRH tmp1, [pOutputBuffer], #NEXT_OUTPUT_PCM @ *pOutputBuffer++ = interpolated result
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@ carry overflow from fraction to integer portion
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ADD pPhaseAccum, pPhaseAccum, tmp2, LSR #(NUM_PHASE_FRAC_BITS - NEXT_INPUT_PCM_SHIFT)
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AND phaseFrac, tmp2, phaseFracMask @ nphaseFrac = frac part
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SUBS numSamples, numSamples, #1
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BGT InterpolationLoop
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@ update and store phase
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STR pPhaseAccum, [pWTVoice, #m_pPhaseAccum]
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STR phaseFrac, [pWTVoice, #m_phaseFrac]
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LDMFD sp!,{r4-r11,lr}
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BX lr
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.end
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