Setting samples in audio clips

The set_channel_data command sets the audio clip samples to desired values.

set_channel_data takes two mandatory arguments and two optional arguments:
- A, an audio clip.
- data, a matrix or vector containing sample data.
- Optionally, offset, a position in A at which data should be written (by default, offset=0).
- Optionally, chn, a channel index or specification (left or right) (by default, the same data is written to all channels or data must be a matrix with one row for each channel).
set_channel_data(A,data ⟨,offset,chn ⟩) returns a modified copy of A in which data is written to A at the desired offset and channel chn.
If data is a matrix, then it must have n rows where n is the number of channels in A. In this case, the fourth argument should be dropped.
If data is a vector, then it is written to the specified channel or to all channels if chn is not given.

In the following example we create an audio clip containing the sine wave and add random noise to its portion.

snd:=createwav(sin(2*pi*440*soundsec(4)))

a sound clip with 176400 samples at 44100 Hz (16 bit, mono

We extract the data after the first and before the third second of the audio.

data:=channel_data(snd,0,range=1.0..3.0):;

Now we create the noise which fades in and out.

noise:=hamming_window(ranv(length(data),normald(0,0.1))):;

Finally we replace the portion of the original clip with the mix of the sine wave and noise.

snd1:=set_channel_data(snd,noise+data,44100,0)

a sound clip with 176400 samples at 44100 Hz (16 bit, mono)