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getp

Reads one output from an opcode object.

Use getp to copy an output that an Opcode object has already produced. You can change which output you read during performance without running the object again.

Syntax

xvalue = getp(object, kindex)

xvalue getp object, kindex

Initialization and performance

object is an Opcode object made with create.

kindex selects an output by position, starting at 0. For an opcode with two outputs, 0 selects the first and 1 selects the second. Supply a whole number within the object's output count. Fractional indexes truncate toward zero, and negative indexes select output 0. An index past the last output causes an error.

xvalue is a placeholder for a variable whose type and rate match the selected output. For example, a k-rate output needs a k-rate destination, and an audio output needs an audio destination. getp does not convert between rates or types. If you change kindex, every selected output must match the destination.

Initialize the object with init or run before reading its outputs. During performance, place getp after run or perf to read the current control cycle's result. getp copies the output at initialization and on performance passes where the call runs. It does not advance the object's state.

For an opcode that has only a performance routine, the first perf call must run before getp reads it during performance. If its outputs are not yet bound, getp skips the initialization copy.

Numeric array outputs are also supported. They use separate destination storage, which must have enough capacity before performance begins. A copy that would require more storage during performance causes an error. Strings, user-defined structures and arrays containing values that need their own cleanup are currently unsupported.

Keep the object alive while reading it. If you pass it between instruments, their sample rates must match and the reader's ksmps must not exceed the object's ksmps.

Instrument p-fields

The index counts opcode outputs. It does not refer to score fields such as p4 or p5, and getp does not accept an Instr object. To read a p-field in the current instrument, use p4, p5 and so on, or pindex for a variable field number.

Examples

This example makes an opcode object with two pitch outputs. getp selects the root or the fifth once per second, and an oscillator plays the selected pitch. Both outputs are k-rate values, so the same destination can read either one.

It uses getp.csd.

Choose between two opcode outputs
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<CsoundSynthesizer>
<CsOptions>
-odac -d -m0
</CsOptions>
<CsInstruments>
sr = 48000
ksmps = 32
nchnls = 1
0dbfs = 1

opcode PitchPair, kk, k
  kRoot xin
  // Output 0 is the root. Output 1 is a perfect fifth above it.
  xout kRoot, kRoot * 1.5
endop

instr ChoosePitch
  pitches:Opcode = create(PitchPair)
  kRoot, kFifth = run(pitches, 220)

  // Alternate between output 0 and output 1 each second.
  kIndex = int(timeinsts()) % 2
  kSelected = getp(pitches, kIndex)

  // Smooth pitch changes and fade the note in and out.
  kFrequency = portk(kSelected, 0.01, 220)
  aEnvelope = linen(0.15, 0.01, p3, 0.1)
  aTone = oscili(aEnvelope, kFrequency)
  out(aTone)

  // Keep the object until this instrument ends.
  delete(pitches)
endin
</CsInstruments>
<CsScore>
i "ChoosePitch" 0 4
e
</CsScore>
</CsoundSynthesizer>

See also

create, init, perf, delete, opcodeinfo, pindex, Instrument definitions, instances and opcode objects

Credits

Author Victor Lazzarini, 2025.

New in Csound 7.