Add exponential smoothing and interpolation

Signed-off-by: Skylar "The Cobra" Widulski <cobra@vern.cc>

README.md

@@ -24,10 +24,15 @@ Below is a list of values and what they do
 * `bgcolor`: Background color
 * `queue-size`: The size of the queue (minimum of 1), delays displaying bars by `queue-size` frames. Useful if desync is noticed
 * `fft`: Whether or not to perform a fourier transform to show frequencies (like `spectrum` mode in most other visualizers)
+* `fft-interpolation`: Number of points to interpolate between fft values. <1 means disable
 * `smoothing`: Smoothing mode. Possible values are:
-    * `#f`: No smoothing
-    * `moving-average`: Moving average
+    * `#f`: No smoothing or interpolation. Disregards `fft-interpolation`
+    * `'none`: No smoothing
+    * `'moving-average`: Moving average
+    * `'exponential`: Simple (basic) exponential smoothing
 * `moving-average-block-size`: Size of the moving average window. Higher is smoother.
+* `exponential-factor`: Exponential smoothing factor, lower is more smooth.
+* `exponential-init-factor`: The first value of the exponentially smoothed list is multiplied by this
 
 # Running
 Either install libyammer.so and yammer.h to their respective systemwide locations, or do the following:
@@ -42,7 +47,7 @@ guile -L . yammer.scm
 
 # Wishlist
 * Native PulseAudio and PipeWire sources
-* More smoothing modes
+* More smoothing modes (one that actually works would be nice)
 * Average over `resolution`
 * Offload some calculations to the GPU
 

config.example.scm

@@ -7,5 +7,8 @@
 (define bgcolor #x2e2016ff)
 (define queue-size 1)
 (define fft #f)
-(define smoothing-mode 'moving-average)
+(define fft-interpolation 0)
+(define smoothing-mode 'none)
 (define moving-average-block-size 25)
+(define exponential-factor 0.5)
+(define exponential-init-factor 10)

yammer.scm

@@ -112,9 +112,10 @@
           (make-rect
             (floor i) 0
             (* (ceiling/ x (length plst)) resolution)
-            ;; Math to make scale a sane value
-            (- y-mid (abs (round/ (* y (car (list-ref plst j)))
-                                  (/ 76800 scale)))))
+            ;; Math to make `scale' a sane value
+            (exact
+              (- y-mid (abs (round/ (* y (car (list-ref plst j)))
+                                    (/ 76800 scale))))))
           bgcolor)
         ;; This value is used twice, define in let statement
         (let ((n (abs (round/ (* y (cadr (list-ref plst j)))
@@ -122,9 +123,10 @@
           (fill-rect
             surf
             (make-rect
-              (floor i) (+ y-mid n)
+              (floor i) (exact (+ y-mid n))
               (* (ceiling/ x (length plst)) resolution)
-              (- y-mid n))
+              (exact
+                (- y-mid n)))
             bgcolor)))))
   ;; Create texture from surface
   (define texture (surface->texture ren surf))
@@ -137,18 +139,46 @@
 
 ;; Smooth non-chunked list `lst' with mode `type'
 (define (smooth lst type)
+  (define input lst)
   (define ret '())
   (define window 0)
+  (if (> fft-interpolation 0)
+    ;; Interpolate FFT values
+    (begin
+      (set! input '())
+      (do ((i 0 (1+ i)))
+          ((>= (1+ i) (length lst)))
+        (set! input (append input (list (list-ref lst i))))
+        (do ((j 0 (1+ j)))
+            ((> j fft-interpolation))
+          (let ((n (- (list-ref lst (1+ i)) (list-ref lst i))))
+            (set! input (append input (list (* (expt (1+ j) (/ n 100000))
+                                               (list-ref lst i))))))))))
   (cond
     ((eq? type 'moving-average)
      (do ((i 1 (1+ i)))
-         ((>= i (- (length lst) moving-average-block-size)))
-       (set! window (list-ref lst (- i 1)))
+         ((>= i (- (length input) moving-average-block-size)))
+       (set! window (list-ref input (- i 1)))
        (do ((j 0 (1+ j)))
            ((>= j moving-average-block-size))
-         (set! window (+ window (list-ref lst (+ i j)))))
+         (set! window (+ window (list-ref input (+ i j)))))
        (set! window (round/ window moving-average-block-size))
-       (set! ret (append ret (list window))))))
+       (set! ret (append ret (list window)))))
+    ((eq? type 'exponential)
+     (do ((i 0 (1+ i)))
+         ((>= i (length input)))
+       (if (= i 0)
+         (set! ret (list (* exponential-init-factor (car input))))
+         (set! ret
+           (append
+             ret
+             (list
+               (/ (+ (list-ref ret (1- i))
+                     (* exponential-factor
+                        (- (list-ref input i)
+                           (list-ref ret (1- i)))))
+                  (/ (log (log (expt i 2))) (log 3)))))))))
+    (else (set! ret input)))
   ret)
 
 ;; Run loop