vmult
vmult — Multiplies a vector in a table by a scalar value.
Performance
kval - scalar value to be multiplied
kelements - number of elements of the vector
kdstoffset - index offset for the destination table (Optional, default = 0)
kverbose - Selects whether or not warnings are printed (Default=0)
vmult multiplies each element of the vector contained in the table ifn by kval, starting from table index idstoffset. This enables you to process a specific section of a table by specifying the offset and the number of elements to be processed. Offset is counted starting from 0, so if no offset is specified (or set to 0), the table will be modified from the beginning.
Note that this opcode runs at k-rate so the value of kval is multiplied every control period. Use with care or you will end up with very large numbers (or use vmult_i).
These opcodes (vadd, vmult, vpow and vexp) perform numeric operations between a vectorial control signal (hosted by the table ifn), and a scalar signal (kval). Result is a new vector that overrides old values of ifn. All these opcodes work at k-rate.
Negative values for kdstoffset are valid. Elements from the vector that are outside the table, will be discarded, and they will not wrap around the table.
If the optional kverbose argument is different to 0, the opcode will print warning messages every k-pass if table lengths are exceeded.
In all these opcodes, the resulting vectors are stored in ifn, overriding the intial vectors. If you want to keep initial vector, use vcopy or vcopy_i to copy it in another table. All these operators are designed to be used together with other opcodes that operate with vectorial signals such as bmscan, vcella, adsynt, adsynt2, etc. They can also be useful in conjunction with the spectral opcodes pvsftw and pvsftr.
![[Note]](images/note.png)
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Note |
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Please note that the elements argument has changed in version 5.03 from i-rate to k-rate. This will change the opcode's behavior in the unusual cases where the i-rate variable ielements is changed inside the instrument, for example in:
instr 1
ielements = 10
vadd 1, 1, ielements
ielements = 20
vadd 2, 1, ielements
turnoff
endin
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Example
Here is an example of the vmult opcode. It uses the file vmult-2.csd.
Example 498. Example of the vmult opcode.
<CsoundSynthesizer> <CsOptions> ; Select audio/midi flags here according to platform ; Audio out Audio in -odac -iadc ;;;RT audio I/O ; For Non-realtime ouput leave only the line below: ; -o cigoto.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> sr=44100 ksmps=128 nchnls=2 instr 1 ifn1 = p4 ival = p5 ielements = p6 idstoffset = p7 kval init 25 vmult ifn1, ival, ielements, idstoffset, 1 endin instr 2 ;Printtable itable = p4 isize = ftlen(itable) kcount init 0 kval table kcount, itable printk2 kval if (kcount == isize) then turnoff endif kcount = kcount + 1 endin </CsInstruments> <CsScore> f 1 0 16 -7 1 16 17 i2 0.0 0.2 1 i1 0.4 0.01 1 2 3 4 i2 0.8 0.2 1 i1 1.0 0.01 1 0.5 5 -3 i2 1.2 0.2 1 i1 1.4 0.01 1 1.5 10 12 i2 1.6 0.2 1 e </CsScore> </CsoundSynthesizer>
Here is another example of the vmult opcode. It uses the file vmult.csd.
Example 499. Example of the vmult opcode.
<CsoundSynthesizer> <CsOptions> ; Select audio/midi flags here according to platform ; Audio out Audio in -odac -iadc ;;;RT audio I/O ; For Non-realtime ouput leave only the line below: ; -o cigoto.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> sr=44100 kr=4410 ksmps=10 nchnls=2 instr 1 ;table playback ar lposcil 1, 1, 0, 262144, 1 outs ar,ar endin instr 2 vcopy 2, 1, 40000 ;copy vector from sample to empty table vmult 5, 10000, 262144 ;scale noise to make it audible vcopy 1, 5, 40000 ;put noise into sample turnoff endin instr 3 vcopy 1, 2, 40000 ;put original information back in turnoff endin </CsInstruments> <CsScore> f1 0 262144 -1 "beats.aiff" 0 4 0 f2 0 262144 2 0 f5 0 262144 21 3 30000 i1 0 4 i2 3 1 s i1 0 4 i3 3 1 s i1 0 4 </CsScore> </CsoundSynthesizer>