The simplest way of playing a sound file from Csound is to use the diskin2 opcode. This opcode reads audio directly from the hard drive location where it is stored, i.e. it does not pre-load the sound file at initialisation time. This method of sound file playback is therefore good for playing back very long, or parts of very long, sound files. It is perhaps less well suited to playing back sound files where dense polyphony, multiple iterations and rapid random access to the file is required. In these situations reading from a function table or buffer is preferable.
diskin2 has additional parameters for speed of playback, and interpolation.
EXAMPLE 06A01_Play_soundfile.csd
<CsoundSynthesizer>
<CsOptions>
-odac ; activate real-time audio output
</CsOptions>
<CsInstruments>
; example written by Iain McCurdy
sr = 44100
ksmps = 32
nchnls = 1
instr 1 ; play audio from disk
kSpeed init 1 ; playback speed
iSkip init 0 ; inskip into file (in seconds)
iLoop init 0 ; looping switch (0=off 1=on)
; read audio from disk using diskin2 opcode
a1 diskin2 "loop.wav", kSpeed, iSkip, iLoop
out a1 ; send audio to outputs
endin
</CsInstruments>
<CsScore>
i 1 0 6
e
</CsScore>
</CsoundSynthesizer>
The traditional method of rendering Csound's audio to disk is to specify a sound file as the audio destination in the Csound command or under <CsOptions>. In fact before real-time performance became a possibility this was the only way in which Csound was used. With this method, all audio that is piped to the output using out, outs etc. will be written to this file. The number of channels that the file will contain will be determined by the number of channels specified in the orchestra header using 'nchnls'. The disadvantage of this method is that we cannot simultaneously listen to the audio in real-time.
EXAMPLE 06A02_Write_soundfile.csd
<CsoundSynthesizer>
<CsOptions>
; audio output destination is given as a sound file (wav format specified)
; this method is for deferred time performance,
; simultaneous real-time audio will not be possible
-oWriteToDisk1.wav -W
</CsOptions>
<CsInstruments>
; example written by Iain McCurdy
sr = 44100
ksmps = 32
nchnls = 1
0dbfs = 1
giSine ftgen 0, 0, 4096, 10, 1 ; a sine wave
instr 1 ; a simple tone generator
aEnv expon 0.2, p3, 0.001 ; a percussive envelope
aSig poscil aEnv, cpsmidinn(p4), giSine ; audio oscillator
out aSig ; send audio to output
endin
</CsInstruments>
<CsScore>
; two chords
i 1 0 5 60
i 1 0.1 5 65
i 1 0.2 5 67
i 1 0.3 5 71
i 1 3 5 65
i 1 3.1 5 67
i 1 3.2 5 73
i 1 3.3 5 78
e
</CsScore>
</CsoundSynthesizer>
Recording audio output to disk whilst simultaneously monitoring in real-time is best achieved through combining the opcodes monitor and fout. 'monitor' can be used to create an audio signal that consists of a mix of all audio output from all instruments. This audio signal can then be rendered to a sound file on disk using 'fout'. 'monitor' can read multi-channel outputs but its number of outputs should correspond to the number of channels defined in the header using 'nchnls'. In this example it is read just in mono. 'fout' can write audio in a number of formats and bit depths and it can also write multi-channel sound files.
EXAMPLE 06A03_Write_RT.csd
<CsoundSynthesizer>
<CsOptions>
-odac ; activate real-time audio output
</CsOptions>
<CsInstruments>
;example written by Iain McCurdy
sr = 44100
ksmps = 32
nchnls = 1
0dbfs = 1
giSine ftgen 0, 0, 4096, 10, 1 ; a sine wave
gaSig init 0; set initial value for global audio variable (silence)
instr 1 ; a simple tone generator
aEnv expon 0.2, p3, 0.001 ; percussive amplitude envelope
aSig poscil aEnv, cpsmidinn(p4), giSine ; audio oscillator
out aSig
endin
instr 2 ; write to a file (always on in order to record everything)
aSig monitor ; read audio from output bus
fout "WriteToDisk2.wav",4,aSig ; write audio to file (16bit mono)
endin
</CsInstruments>
<CsScore>
; activate recording instrument to encapsulate the entire performance
i 2 0 8.3
; two chords
i 1 0 5 60
i 1 0.1 5 65
i 1 0.2 5 67
i 1 0.3 5 71
i 1 3 5 65
i 1 3.1 5 67
i 1 3.2 5 73
i 1 3.3 5 78
e
</CsScore>
</CsoundSynthesizer
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