feat(dsp): update DelayLine ctor, freqBin, update pkg

thi-ng · Jan 3, 2020 · 228a81e · 228a81e
1 parent 3970aca
commit 228a81e
Show file tree

Hide file tree

Showing 3 changed files with 28 additions and 4 deletions.
diff --git a/packages/dsp/package.json b/packages/dsp/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@thi.ng/dsp",
     "version": "1.0.18",
-    "description": "Assorted oscillators / waveform generators & DSP utils",
+    "description": "Assorted oscillators / wave gens, FFT, windowing functions & DSP utils",
     "module": "./index.js",
     "main": "./lib/index.js",
     "umd:main": "./lib/index.umd.js",
@@ -39,6 +39,7 @@
     },
     "dependencies": {
         "@thi.ng/api": "^6.6.0",
+        "@thi.ng/checks": "^2.4.2",
         "@thi.ng/math": "^1.5.1"
     },
     "keywords": [

diff --git a/packages/dsp/src/delay.ts b/packages/dsp/src/delay.ts
@@ -1,3 +1,6 @@
+import { Fn0 } from "@thi.ng/api";
+import { isFunction } from "@thi.ng/checks";
+
 /**
  * Ring buffer / delay line for arbitrary values w/ support for tapping
  * at any delay time (within configured buffer size).
@@ -7,10 +10,26 @@ export class DelayLine<T> {
     readPos: number;
     writePos: number;
 
-    constructor(n: number, empty: T) {
-        this.buf = new Array(n).fill(empty);
+    /**
+     * Constructs new delay line of size `n` and initializes all
+     * elements to `empty`. If the latter is a function, the buffer will
+     * be initialized with the results of that function (called for each
+     * element).
+     *
+     * @param n
+     * @param empty
+     */
+    constructor(n: number, empty: T | Fn0<T>) {
         this.writePos = n - 1;
         this.readPos = 0;
+        this.buf = new Array(n);
+        if (isFunction(empty)) {
+            for (let i = 0; i < n; i++) {
+                this.buf[i] = empty();
+            }
+        } else {
+            this.buf.fill(empty);
+        }
     }
 
     /**
@@ -45,6 +64,10 @@ export class DelayLine<T> {
         this.buf[this.writePos] = x;
     }
 
+    /**
+     * Moves read & write cursors one step forward. Useful for skipping
+     * elements and/or to create gaps in the delay line.
+     */
     step() {
         const n = this.buf.length;
         ++this.writePos >= n && (this.writePos -= n);

diff --git a/packages/dsp/src/fft.ts b/packages/dsp/src/fft.ts
@@ -326,7 +326,7 @@ export const spectrumPhase = (
  * @param fs - sample rate
  * @param n - window size
  */
-export const freqBin = (f: number, fs: number, n: number) => (f * n) / fs;
+export const freqBin = (f: number, fs: number, n: number) => ((f * n) / fs) | 0;
 
 /**
  * Returns frequency for given FFT bin index, sample rate and window