audio-player: added js adpcm decode func

cmd/audio-player/index.html

@@ -5,7 +5,6 @@
     <meta charset="utf-8">
     <title>Audio Player</title>
     <script type="text/javascript" src="pcm-player.min.js"></script>
-    <script src="wasm_exec.js"></script>
     <script type="text/javascript" src="main.js"></script>
     <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"
         integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

cmd/audio-player/main.js

@@ -1,60 +1,3 @@
-const go = new Go()
-// memoryBytes is an Uint8Array pointing to the webassembly linear memory.
-let memoryBytes;
-let bytes;
-let mod, inst
-console.log("Initializing wasm...")
-WebAssembly.instantiateStreaming(
-    fetch('lib.wasm'), go.importObject).then(
-    result => {
-        mod = result.module
-        inst = result.instance
-        memoryBytes = new Uint8Array(inst.exports.mem.buffer)
-        console.log("Initialization complete.")
-        run()
-    }
-)
-
-async function run() {
-    await go.run(inst)
-    inst = await WebAssembly.instantiate(mod, go.importObject) // reset instance
-}
-
-let memPointer
-
-// gotMem sets the webassembly linear memory with the data buffer result
-// at the slice header pointer passed from Go.
-function gotMem(pointer) {
-    memPointer = pointer
-    memoryBytes.set(bytes, pointer);
-    // Now the data can be loaded from the slice.
-    loadData();
-}
-
-// // displayImage takes the pointer to the target image in the wasm linear memory
-// // and its length. Gets the resulting byte slice and creates an image blob.
-// function displayImage(pointer, length) {
-//     let resultBytes = memoryBytes.slice(pointer, pointer + length);
-//     let blob = new Blob([resultBytes], {
-//         'type': imageType
-//     });
-//     document.getElementById('targetImg').src = URL.createObjectURL(blob);
-// }
-
-// document.getElementById('input').addEventListener('change', function () {
-//     let reader = new FileReader();
-
-//     reader.onload = (ev) => {
-//         bytes = new Uint8Array(ev.target.result);
-//         initMem(bytes.length);
-//         let blob = new Blob([bytes], {
-//             'type': imageType
-//         });
-//         document.getElementById("sourceImg").src = URL.createObjectURL(blob);
-//     };
-//     imageType = this.files[0].type;
-//     reader.readAsArrayBuffer(this.files[0]);
-// });
 window.onload = function () {
 
     document.getElementById('input').addEventListener('change', function () {
@@ -64,12 +7,6 @@ window.onload = function () {
         reader.onload = event => {
             bytes = new Uint8Array(event.target.result)
 
-            initMem(bytes.length)
-
-            let resultBuffer = new ArrayBuffer(getDecLen());
-            let resultBytes = new Uint8Array(resultBuffer)
-            resultBytes.set(memoryBytes.slice(memPointer, memPointer + getDecLen()))
-
             console.log("playing file")
             var player = new PCMPlayer({
                 encoding: '16bitInt',
@@ -77,7 +14,7 @@ window.onload = function () {
                 sampleRate: 48000,
                 flushingTime: 2000
             });
-            player.feed(resultBytes)
+            player.feed(bytes)
         }
         reader.onerror = error => reject(error)
         reader.readAsArrayBuffer(input)

cmd/audio-player/server.go

@@ -4,7 +4,6 @@ import (
     "flag"
     "log"
     "net/http"
-	"strings"
 )
 
 var (
@@ -15,18 +14,5 @@ var (
 func main() {
     flag.Parse()
     log.Printf("listening on %q...", *listen)
-	h := wasmContentTypeSetter(http.FileServer(http.Dir(*dir)))
-	err := http.ListenAndServe(*listen, h)
-	if err != http.ErrServerClosed {
-		log.Fatal(err)
-	}
-}
-
-func wasmContentTypeSetter(h http.Handler) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if strings.HasSuffix(r.URL.Path, ".wasm") {
-			w.Header().Set("content-type", "application/wasm")
-		}
-		h.ServeHTTP(w, r)
-	})
+    log.Fatal(http.ListenAndServe(*listen, http.FileServer(http.Dir(*dir))))
 }

codec/adpcm/adpcm.go

@@ -295,7 +295,7 @@ func (d *Decoder) Write(b []byte) (int, error) {
 
 	// For each byte, seperate it into two nibbles (each nibble is a compressed sample),
 	// then decode each nibble and output the resulting 16-bit samples.
-	// If padding flag is true (Adpcm[3]), only decode up until the last byte, then decode that separately.
+	// If padding flag is true (b[3]), only decode up until the last byte, then decode that separately.
 	for i := headBytes; i < len(b)-int(b[3]); i++ {
 		twoNibs := b[i]
 		nib2 := byte(twoNibs >> 4)

codec/adpcm/adpcm.js

@@ -0,0 +1,72 @@
+const indexTable = [
+	-1, -1, -1, -1, 2, 4, 6, 8,
+	-1, -1, -1, -1, 2, 4, 6, 8
+]
+
+const stepTable = [
+	7, 8, 9, 10, 11, 12, 13, 14,
+	16, 17, 19, 21, 23, 25, 28, 31,
+	34, 37, 41, 45, 50, 55, 60, 66,
+	73, 80, 88, 97, 107, 118, 130, 143,
+	157, 173, 190, 209, 230, 253, 279, 307,
+	337, 371, 408, 449, 494, 544, 598, 658,
+	724, 796, 876, 963, 1060, 1166, 1282, 1411,
+	1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
+	3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
+	7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
+	15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
+	32767
+]
+
+const byteDepth = 2, // We are working with 16-bit samples. TODO(Trek): make configurable.
+	initSamps = 2, // Number of samples used to initialise the encoder.
+	initBytes = initSamps * byteDepth,
+	headBytes = 4, // Number of bytes in the header of ADPCM.
+	samplesPerEnc = 2, // Number of sample encoded at a time eg. 2 16-bit samples get encoded into 1 byte.
+	bytesPerEnc = samplesPerEnc * byteDepth,
+	compFact = 4; // In general ADPCM compresses by a factor of 4.
+
+let est, // Estimation of sample based on quantised ADPCM nibble.
+	idx, // Index to step used for estimation.
+	step;
+
+function decode(b) {
+	// b should be a Uint8Array
+	if (!(b instanceof Uint8Array)) {
+		console.log("Error: data is not a Uint8Array");
+		return;
+	}
+
+	// Initialize Decoder with first 4 bytes of b.
+	est = (new Uint16Array(b.slice(0, 2).buffer))[1];
+	idx = b[byteDepth];
+	step = stepTable[idx];
+
+	var result = new Uint8Array(b.slice(0, 2));
+
+	for (var i = headBytes; i < b.length - b[3]; i++) {
+		var twoNibs = b[i];
+		var nib2 = twoNibs >> 4;
+		var nib1 = (nib2 << 4) ^ twoNibs
+		var firstBytes = decodeSample(nib1)
+		concat(result, firstBytes)
+
+		var secondBytes = decodeSample(nib2)
+		concat(result, secondBytes)
+	}
+	if (b[3] == 1) {
+		var padNib = b[b.length - 1]
+		var samp = decodeSample(padNib)
+		concat(result, samp)
+	}
+
+	return result;
+}
+
+// concat concatenates TypedArrays a and b of same type.
+function concat(a, b) {
+	var c = new(a.constructor)(a.length + b.length);
+	c.set(a, 0);
+	c.set(b, a.length);
+	return c;
+}