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tableikt

Provides k-rate control over table numbers.

Function tables are read with linear interpolation.

The standard Csound opcode tablei, when producing a k- or a-rate result, can only use an init-time variable to select the table number. tableikt accepts k-rate control as well as i-time. In all other respects they are similar to the original opcodes.

Syntax

ares tableikt xndx, kfn [, ixmode] [, ixoff] [, iwrap]
kres tableikt kndx, kfn [, ixmode] [, ixoff] [, iwrap]

Initialization

ixmode -- if 0, xndx and ixoff ranges match the length of the table. if non-zero xndx and ixoff have a 0 to 1 range. Default is 0

ixoff -- if 0, total index is controlled directly by xndx, ie. the indexing starts from the start of the table. If non-zero, start indexing from somewhere else in the table. Value must be positive and less than the table length (ixmode = 0) or less than 1 (ixmode not equal to 0). Default is 0.

iwrap -- if iwrap = 0, Limit mode: when total index is below 0, then final index is 0.Total index above table length results in a final index of the table length - high out of range total indexes stick at the upper limit of the table. If iwrap not equal to 0, Wrap mode: total index is wrapped modulo the table length so that all total indexes map into the table. For instance, in a table of length 8, xndx = 5 and ixoff = 6 gives a total index of 11, which wraps to a final index of 3. Default is 0.

Performance

kndx -- Index into table, either a positive number range matching the table length (ixmode = 0) or a 0 to 1 range (ixmode not equal to 0).

xndx -- matching the table length (ixmode = 0) or a 0 to 1 range (ixmode not equal to 0)

kfn -- Table number. Must be >= 1. Floats are rounded down to an integer. If a table number does not point to a valid table, or the table has not yet been loaded (GEN01) then an error will result and the instrument will be de-activated.

⚠ Caution with k-rate table numbers

At k-rate, if a table number of < 1 is given, or the table number points to a non-existent table, or to one which has a length of 0 (it is to be loaded from a file later) then an error will result and the instrument will be deactivated. kfn must be initialized at the appropriate rate using init. Attempting to load an i-rate value into kfn will result in an error.

Examples

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

Example of the tableikt opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;realtime audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o tableikt.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

instr 1

ilowfn  = p4                                    ;lowest ftable wave
ihighfn = p5                                    ;highest ftable wave

kswpenv line 1, p3, 0                           ;sweep envelope, calculate current table pair and interpolation amount
inumtables = ihighfn - ilowfn                   ;1 less than number of tables
kfn1    = int(kswpenv*inumtables) + ilowfn
        printks "play table no: %d\n", 1, kfn1
kfn2    = kfn1 + 1
kinterp = frac(kswpenv*inumtables)              
ixmode  = 1                                     ;read tables with phasor
aphase  phasor  40      
asig    tableikt aphase, kfn1, ixmode           ;normalized index
   if kswpenv == 1.0 kgoto skipfn2              ;if kfn1 is last table, there is no kfn2
        asig2   tableikt aphase, kfn2, ixmode
   skipfn2:
   amix ntrpol  asig, asig2, kinterp            ;interpolate between tables and output
        outs    amix*.5, amix*.5

endin
</CsInstruments>
<CsScore>
f 1  0 16384 10 1  
f 2  0 16384 10 1 .5  
f 3  0 16384 1 "fox.wav" 0 0 0                          ;a sample
f 4  0 16384 10 1 .5 .3 .25 .2 .16 .14 .125 .111        ;sawtooth 
f 5  0 16384 10 1 .4 .3 .25 .2
f 6  0 16384 10 1 .3 .3 .25 .2 .16 
f 7  0 16384 10 1  1  1  1  .7 .5  .3  .1               ;pulse
f 8  0 16384 1 "drumsMlp.wav" 0 0 0                     ;a sample

i 1 0 10 1 8
e
</CsScore>
</CsoundSynthesizer>

Its output should include lines like these:

play table no: 8
play table no: 7
play table no: 6
.....
play table no: 2
play table no: 1

See also

Table Reading with Dynamic Selection

Credits

Author: Robin Whittle
Australia
May 1997

New in version 3.47