diff
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## diff

diff — Modify a signal by differentiation.

## Description

Modify a signal by differentiation.

## Syntax

    ares diff asig [, iskip]

    kres diff ksig [, iskip]

## Initialization

iskip (optional) -- initial disposition of internal save space (see reson). The default value is 0.

## Performance

integ and diff perform integration and differentiation on an input control signal or audio signal. Each is the converse of the other, and applying both will reconstruct the original signal. Since these units are special cases of low-pass and high-pass filters, they produce a scaled (and phase shifted) output that is frequency-dependent. Thus diff of a sine produces a cosine, with amplitude 2 * sin(pi * Hz / sr) that of the original (for each component partial); integ will inversely affect the magnitudes of its component inputs. With this understanding, these units can provide useful signal modification.

## Examples

Here is an example of the diff opcode. It uses the file diff.csd.

Example 111. Example of the diff opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    ; Select audio/midi flags here according to platform
    ; Audio out   Audio in    No messages
    -odac           -iadc     -d     ;;;RT audio I/O
    ; For Non-realtime ouput leave only the line below:
    ; -o diff.wav -W ;;; for file output any platform
    </CsOptions>
    <CsInstruments>

    ; Initialize the global variables.
    sr = 44100
    kr = 4410
    ksmps = 10
    nchnls = 1

    ; Instrument #1 -- a normal instrument.
    instr 1
      ; Generate a band-limited pulse train.
      asrc buzz 20000, 440, 20,  1

      out asrc
    endin

    ; Instrument #2 -- a differentiated instrument.
    instr 2
      ; Generate a band-limited pulse train.
      asrc buzz 20000, 440, 20,  1

      ; Emphasize the highs.
      a1 diff asrc

      out a1
    endin

    </CsInstruments>
    <CsScore>

    ; Table #1, a sine wave.
    f 1 0 16384 10 1

    ; Play Instrument #1 for one second.
    i 1 0 1
    ; Play Instrument #2 for one second.
    i 2 1 1
    e

    </CsScore>
    </CsoundSynthesizer>

## See Also

downsamp, integ, interp, samphold, upsamp

## Credits

Example written by Kevin Conder.

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