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File List | 1994-09-02 | 17.7 KB | 509 lines

;*************************************************************** ; ; A stereo reverb for the DSP56001 signal processor. ; Developed by Quinn Jensen (jensenq@qcj.icon.com) using ; Dr. Vercoe and company's csound code as a reference for the ; configuration and gain values. ; ; NOTE - A much improved reverb algorithm is in sixcomb.a56 ; ; This program fragment implements a stereo reberb effect ; on a DSP56001 processor. The "depth" and wet/dry mix are ; adjustable. The following filter configuration is employed: ; ; ; Left in ------+------- "dry" gain -----------> sum -----> Left out ; | ^ ; v | ; sum --> reverb --> "wet" gain -----+ ; ^ | ; | v - ; Right in -----+------- "dry" gain -----------> sum -----> Right out ; ; ; Note that the reverb path output is negated before summing with the ; right input signal. This throws in 180 degrees of phase shift ; making for interesting results even with mono inputs ; (i.e. Left in == Right in). ; ; The reverb element looks like this: ; ; ; Input ----+-----> comb1 ------+ ; | | ; +-----> comb2 ---\ v ; | sum -----> allpass1 --> allpass2 ---> output ; +-----> comb3 ---/ ^ ; | | ; +-----> comb4 ------+ ; ; Each comb stage looks like this: ; ; +---- gain <-----+ ; | | ; v | ; Input ---> gain ----> sum ---> delay ---+--> out ; ; ; The allpass stages look like: ; ; +--------- gain <---------+ ; | | ; v | ; Input ---> gain --+--> sum ---> delay ---> sum ---+----> out ; | ^ ; | | ; +--------> gain ----------+ ; ; or, ; ; +-------> gain ----+ ; | | ; | v ; Input ---> gain ----> sum --+--> delay --+--> sum -----> out ; ^ | ; | | ; +----- gain <-----+ ; ; ; I've seen both configurations in the literature, so I plotted the ; Z-transform and they are equivalent in the steady state. They are indeed ; all-pass in the steady state but are supposed to have a subtle, discernable ; effect in "transient" audio signals. ; ; I think it could really use a couple more comb stages to fill in some of the ; graininess. The best possible "diffusion" is desired. By the way, ; I'd enjoy seeing any optimizations to the code. ; ;hardware specific initialization code include "tdsg.a56" ;*************************************************************** ; ; Data and constants ; ;*************************************************************** P:0076 dot ;remember where we were in P-space X:0010 org x:$10 ;put runtime variables in on-chip X-space ; A spreadsheet was used to calculate the following numbers ; ; The gain of each feedback stage is given by ; ; feedback gain = exp(delay * ln(.001)/duration) ; ; where "delay" is the delay of the comb or allpass stage in seconds, ; and "duration" is the time in seconds for the reverberated sound ; to decay to 1/1000 of its original amplitude. ; ; Reverb filter lengths and coefficients ; Sun Aug 4 16:36:16 1991 ; ; Sample rate 32.5520830 kHz ; Reverb duration 4.0000000 s ; ; stage delay(ms) length gain actual ; ----------------------------------------------------- ; Comb1 29.7000000 967 0.9500031 29.71 ; Comb2 37.1000000 1208 0.9379399 37.11 ; Comb3 41.1000000 1338 0.9314831 41.10 ; Comb4 43.7000000 1423 0.9273101 43.71 ; All-1 5.0000000 163 0.9914025 5.01 ; All-2 1.7000000 55 0.9970685 1.69 0.340909 in_atten equ 0.3409091 0.0416667 comb_atten equ 0.0416667 0.4 dry_init equ 0.4000000 ; initial "dry" gain 0.99 reverb_init equ 0.9900000 ; initial "wet" gain ; comb 1 data and parameters 004000 c1d equ $4000 X:0010 004000 c1r dc c1d 0003C6 c1m equ 966 0.950003 c1c equ 0.9500031 ; comb 2 data and parameters 004800 c2d equ c1d+ 2048 X:0011 004800 c2r dc c2d 0004B7 c2m equ 1207 0.93794 c2c equ 0.9379399 ; comb 3 data and parameters 005000 c3d equ c2d+ 2048 X:0012 005000 c3r dc c3d 000539 c3m equ 1337 0.931483 c3c equ 0.9314831 ; comb 4 data and parameters 005800 c4d equ c3d+ 2048 X:0013 005800 c4r dc c4d 00058E c4m equ 1422 0.92731 c4c equ 0.9273101 ; allpass 1 data and parameters 006000 a1d equ c4d+ 2048 X:0014 006000 a1r dc a1d 0000A2 a1m equ 162 0.991403 a1c equ 0.9914025 ; allpass 2 data and parameters 006800 a2d equ a1d+ 2048 X:0015 006800 a2r dc a2d 000036 a2m equ 54 0.997068 a2c equ 0.9970685 Y:0000 org y:$0 0.99 reverb_on equ reverb_init 000000 reverb_off equ 0 Y:0000 reverb_gain Y:0000 7EB852 dc reverb_on Y:0001 dry_gain Y:0001 333333 dc dry_init P:0076 org p:dot ;go back to P-space ;***************************************************** ; ; reverb initialization code ; ;***************************************************** P:0076 hf_init P:0076 00000C rts ;***************************************************** ; ; run-time controls ; ;***************************************************** P:0077 eff1_on ;enable reverb P:0077 46F400 move #reverb_on,y0 P:0078 7EB852 P:0079 4E0000 move y0,y:<reverb_gain P:007A 00000C rts P:007B eff1_off ;bypass reverb P:007B 46F400 move #reverb_off,y0 P:007C 000000 P:007D 4E0000 move y0,y:<reverb_gain P:007E 00000C rts ;***************************************************** ; ; interrupt time calculations ; ;***************************************************** ; ; fs = 32.552083 kHz ; P:007F hf_comp P:007F 0D0066 jsr <saveregs ; ; L/R mix ; P:0080 45F413 clr a #in_atten,x1 ;clr a, get scale for mix P:0081 2BA2E9 P:0082 448000 move x:<in_l,x0 ;get left in P:0083 440200 move x0,x:<in_ls ;save P:0084 4481A3 macr x0,x1,a x:<in_r,x0 ;a = scale * left, get right P:0085 4403A3 macr x0,x1,a x0,x:<in_rs ;a += scale * right, save right P:0086 21C61B clr b a,y0 ;y0 goes to the combs, b is sum ; ; comb 1 ; P:0087 609000 move x:<c1r,r0 P:0088 05F420 movec #c1m,m0 P:0089 0003C6 P:008A 20CE00 move y0,a P:008B 45E000 move x:(r0),x1 P:008C 44F468 add x1,b #c1c,x0 P:008D 7999B4 P:008E 2000A3 macr x0,x1,a P:008F 565800 move a,x:(r0)+ P:0090 601000 move r0,x:<c1r ; ; comb 2 ; P:0091 609100 move x:<c2r,r0 P:0092 05F420 movec #c2m,m0 P:0093 0004B7 P:0094 20CE00 move y0,a P:0095 45E000 move x:(r0),x1 P:0096 44F468 add x1,b #c2c,x0 P:0097 780E6A P:0098 2000A3 macr x0,x1,a P:0099 565800 move a,x:(r0)+ P:009A 601100 move r0,x:<c2r ; ; comb 3 ; P:009B 609200 move x:<c3r,r0 P:009C 05F420 movec #c3m,m0 P:009D 000539 P:009E 20CE00 move y0,a P:009F 45E000 move x:(r0),x1 P:00A0 44F468 add x1,b #c3c,x0 P:00A1 773AD7 P:00A2 2000A3 macr x0,x1,a P:00A3 565800 move a,x:(r0)+ P:00A4 601200 move r0,x:<c3r ; ; comb 4 ; P:00A5 609300 move x:<c4r,r0 P:00A6 05F420 movec #c4m,m0 P:00A7 00058E P:00A8 20CE00 move y0,a P:00A9 45E000 move x:(r0),x1 P:00AA 44F468 add x1,b #c4c,x0 P:00AB 76B219 P:00AC 2000A3 macr x0,x1,a P:00AD 565800 move a,x:(r0)+ P:00AE 601300 move r0,x:<c4r ; ; scale ; P:00AF 12B400 move #comb_atten,x0 b,y0 P:00B0 055556 P:00B1 2000D9 mpyr x0,y0,b ; ; allpass 1 ; P:00B2 609400 move x:<a1r,r0 P:00B3 05F420 movec #a1m,m0 P:00B4 0000A2 P:00B5 44F400 move #a1c,x0 P:00B6 7EE647 P:00B7 45E000 move x:(r0),x1 P:00B8 20AEAB macr x0,x1,b x1,a P:00B9 21E600 move b,y0 P:00BA 5758D7 macr -x0,y0,a b,x:(r0)+ P:00BB 601400 move r0,x:<a1r ; ; allpass 2 ; P:00BC 609500 move x:<a2r,r0 P:00BD 05F420 movec #a2m,m0 P:00BE 000036 P:00BF 44F400 move #a2c,x0 P:00C0 7F9FF1 P:00C1 45E000 move x:(r0),x1 P:00C2 20AFA3 macr x0,x1,a x1,b P:00C3 21C600 move a,y0 P:00C4 5658DF macr -x0,y0,b a,x:(r0)+ P:00C5 601500 move r0,x:<a2r ; ; output mix ; P:00C6 21E400 move b,x0 P:00C7 4E8000 move y:<reverb_gain,y0 P:00C8 4E81D9 mpyr x0,y0,b y:<dry_gain,y0 P:00C9 448200 move x:<in_ls,x0 P:00CA 21EE00 move b,a P:00CB 4483D3 macr x0,y0,a x:<in_rs,x0 P:00CC 5604DB macr x0,y0,b a,x:<out_l P:00CD 570500 move b,x:<out_r P:00CE 0D006F jsr <restregs P:00CF 00000C rts end Summary of psect usage section seg base last top used avail total ------------------------------------------------------------------------- Symbol Table ------------------------------------- ssi_int 000061 ssix 000010 eff1_off 00007B eff1_on 000077 in_atten 0.3409091000 init_stereo 000059 start 000040 in_rs 000003 in_ls 000002 in_r 000001 in_l 000000 dot 000076 comb_atten 0.0416667000 mainloop 000060 hf_comp 00007F hf_init 000076 saveregs 000066 savey 00000B savex 00000A saveb2 000009 saveb10 000008 savea2 000007 savea10 000006 dry_gain 000001 dry_init 0.4000000000 reverb_gain 000000 reverb_off 000000 reverb_on 0.9900000000 reverb_init 0.9900000000 restregs 00006F out_r 000005 out_l 000004 m_scl1 00000F m_scl0 00000E m_scl 00C000 m_ssl1 00000D m_ssl0 00000C m_ssl 003000 m_hpl1 00000B m_hpl0 00000A m_hpl 000C00 m_ibl2 000005 m_ibl1 000004 m_ibl0 000003 m_ibl 000038 m_ial2 000002 m_ial1 000001 m_ial0 000000 m_ial 000007 m_ipr 00FFFF m_rdf 000007 m_tde 000006 m_roe 000005 m_tue 000004 m_rfs 000003 m_tfs 000002 m_if1 000001 m_if0 000000 m_if 000002 m_srie 00000F m_stie 00000E m_sre 00000D m_ste 00000C m_mod 00000B m_gck 00000A m_syn 000009 m_fsl 000008 m_sckd 000005 m_scd2 000004 m_scd1 000003 m_scd0 000002 m_scd 00001C m_of1 000001 m_of0 000000 m_of 000003 m_psr 00000F m_wl1 00000E m_wl0 00000D m_wl 006000 m_dc 001F00 m_pm 0000FF m_tsr 00FFEE m_sr 00FFEE m_crb 00FFED m_cra 00FFEC m_tx 00FFEF m_rx 00FFEF m_tcm 00000F m_rcm 00000E m_scp 00000D m_cod 00000C m_cd 000FFF m_r8 000007 m_fe 000006 m_pe 000005 m_or 000004 m_idle 000003 m_rdrf 000002 m_tdre 000001 m_trne 000000 m_tmie 00000D m_tie 00000C m_rie 00000B m_ilie 00000A m_te 000009 m_re 000008 m_woms 000007 m_rwi 000006 m_wake 000005 m_sbk 000004 m_wds2 000002 m_wds1 000001 m_wds0 000000 m_wds 000003 m_sccr 00FFF2 m_ssr 00FFF1 m_scr 00FFF0 m_stxa 00FFF3 m_stxh 00FFF6 m_stxm 00FFF5 m_stxl 00FFF4 m_srxh 00FFF6 m_srxm 00FFF5 m_srxl 00FFF4 m_dma 000007 m_hf1 000004 m_hf0 000003 m_hf 000018 m_hcp 000002 m_htde 000001 m_hrdf 000000 m_hf3 000004 m_hf2 000003 m_hcie 000002 m_htie 000001 m_hrie 000000 m_htx 00FFEB m_hrx 00FFEB m_hsr 00FFE9 m_hcr 00FFE8 m_pcd 00FFE5 m_pcddr 00FFE3 m_pcc 00FFE1 m_pbd 00FFE4 m_pbddr 00FFE2 m_pbc 00FFE0 m_bcr 00FFFE a1c 0.9914025000 a1m 0000A2 a1r 000014 a1d 006000 c3c 0.9314831000 c3m 000539 c3r 000012 c3d 005000 c2c 0.9379399000 c2m 0004B7 c2r 000011 c2d 004800 c1c 0.9500031000 c1m 0003C6 c1r 000010 c1d 004000 a2c 0.9970685000 a2m 000036 a2r 000015 a2d 006800 c4c 0.9273101000 c4m 00058E c4r 000013 c4d 005800 errors=0