[LAU] mixing multiple samples into a single audio file based on start times

[Kjetil S. Matheussen]

Erik Nomitch:
>
> Hi,
>
> I'm making a random "beat" generator based on a directory tree of
> samples and a map file.  Currently, it shuffles sample order and
> creates a list of samples and their corresponding start time (example
> list below).
>
> I need a good way to mix all of these seperate samples into one single
> audio file based on the time at which each starts at.  Any
> recommendations or thoughts would be appreciated.  File format doesn't
> matter, I'll use whatever is easiest.
>
> Thanks,
> Erik Nomitch
>
> ex:
> at: 0.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2A.wav
> at: 2.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2S.wav
> at: 4.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1A.wav
> at: 6.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1S.wav
> at: 8.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_aOrig.wav
> at: 10.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01.wav
> at: 12.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_ST.wav
> at: 14.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_VT1.wav
> at: 4.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2A.wav
> at: 6.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2S.wav
> at: 8.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1A.wav
> at: 10.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1S.wav
> at: 12.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_aOrig.wav
> at: 14.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01.wav
> at: 16.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_ST.wav
> at: 18.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_VT1.wav
> at: 4.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2A.wav
> at: 8.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_C2S.wav
> at: 12.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1A.wav
> at: 16.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_T1S.wav
> at: 20.0 play /home/tux/.projects/elign/808/clap/808Clap-Kult_aOrig.wav
> at: 24.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01.wav
> at: 28.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_ST.wav
> at: 32.0 play /home/tux/.projects/elign/808/clap/808Clap-R8_01_VT1.wav
> etc...
>

Below is some code I have hacked together for Snd to do this.
Compile snd with the "--with-guile" option, save your txt
above ("at: etc.") into a file called "score.txt", start 
Snd, and paste the code below into the terminal you started
snd in.

Alternatively, you can save the code below into a
file, and use the "-b" option to start a gui-less
Snd which load and runs a specified script file.


(define (map-file filename func)
   (let* ((fd (open-file filename "r"))
 	 (line (read-line fd))
          (ret '()))
     (while (not (eof-object? line))
       (set! ret (cons (func line) ret))
       (set! line (read-line fd)))
     (reverse ret)))

(define* (fileplay seconds filename)
   (let* ((samples (seconds->samples seconds))
          (end (+ (mus-sound-frames filename) samples)))
     (for-each (lambda (ch)
                 (define fd (make-readin filename :channel ch))
                 (run
                  (lambda ()
                    (do ((i samples (1+ i))) ((= i end))
                      (out-any i (readin fd) ch)))))
               (iota (mus-sound-chans filename)))))

(define (create score samplerate channels outfile)
   (set! (optimization) 6)
   (primitive-eval `(with-sound (:srate ,samplerate :channels ,channels :output ,outfile)
                                ,@(map (lambda (start filename)
                                         `(fileplay ,start ,filename))
                                       (map string->number (map cadr (map-file score (lambda (l) (string-split l #\space)))))
                                       (map cadddr (map-file score (lambda (l) (string-split l #\space))))))))

(create "score.txt" 44100 2 "/tmp/test.wav")