Hi everyone,
Do you see a possibility to add custom attack and release curves to a compressor opcode or any other way to realise that?
I want to match curves from different compressors.
Thanks!
//Rootnote
Attack, release shapes compressor
sorry @rootnote, I’ve no idea as I’ve never used any of the compressors in Csound. Maybe you can roll your own compressor to do this?
Hi.
If you use follow as the envelope follower, you can roll your own compressor with separate control of attack and release times. Then, to control the shape of each segment, you can run it through a pow opcode. Writing this on my phone, so I don’t have full examples from my teaching at hand. Can supply those later if you need them 
Øyvind
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Meant follow2 due envelope follower. Autocorrect ate the '2’
Here’s a compressor that uses follow2 as the envelope follower. I have not used shaping on the envelope, but IIRC follow2 is roughly exponential. I think you will get most things done with just adjusting the attack and release times.
<CsoundSynthesizer>
<CsOptions>
;-odac0 -b1024 -B2048 ; realtime audio out
-ocompressor3.wav ; output to audio file
</CsOptions>
<CsInstruments>
sr = 48000
ksmps = 64
nchnls = 2
0dbfs = 1
;***************************************************
;ftables
;***************************************************
giSample2 ftgen 0, 0, 0, 1, "MoodySlide2_110.wav", 0, 0, 0
;***************************************************
; Simple Compressor, ratio expressed in dB,
; lookahead time in milliseconds.
; Using envelope follower instead of simple amplitude tracking, so we can adjust attack and release time separately
;***************************************************
instr 2
iamp = ampdbfs(p4) ; Amp in -dB
kthresh = p5 ; compression threshold
kratio = p6 ; compression ratio
kattack = p7 ; attack time
krelease = p8 ; release time
; audio generator
aenv linseg 0,0.0001, 1, 1, 1, 0.1, 0.2, 1, 0.2, 1, 0
a1 loscil iamp, 1, giSample2, 1 ; test sample
; compressor
arms follow2 a1, kattack/1000, krelease/1000 ; envelope follower
karms downsamp arms ; workaround for dbfsamp (should take a-rate input)
arms_dB = upsamp(dbfsamp(karms)) ; convert to dB scale and upsample
aovershoot = arms_dB - kthresh ; how much over the threshold are we?
atarget = kthresh + (aovershoot*(1/kratio)) ; target output level (with current input level, threshold and ratio)
ampMod_dB = atarget - arms_dB ; difference from target = adjust amount
ampMod_dB limit ampMod_dB, -150, 0 ; do not adjust unless negative
ampMod = ampdbfs(ampMod_dB) ; convert back to normalized scale
acomp = a1*ampMod ; apply amplitude modification
; audio out
outs acomp, acomp
endin
;***************************************************
</CsInstruments>
<CsScore>
;compression
; start dur amp thresh ratio attack release
i2 0 3 0 -20 8 60 100
i2 ^+4 3 0 -20 8 15 100
i2 ^+4 3 0 -20 8 2 20
i2 ^+4 3 0 -20 8 30 20
i2 ^+4 3 0 -20 8 60 20
</CsScore>
</CsoundSynthesizer>
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