Mercurial > hg > webaudioevaluationtool

changeset 2642:77204f78386a

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#3: Added resampler from JS-xtract into resampler.js. Automatically use to match sample rates
author Nicholas Jillings <nicholas.jillings@mail.bcu.ac.uk>
date Thu, 19 Jan 2017 14:48:02 +0000
parents 757e3956845c
children 52e51b15f808
files index.html js/core.js js/resample.js test.html
diffstat 4 files changed, 175 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/index.html	Thu Jan 19 13:12:31 2017 +0000
+++ b/index.html	Thu Jan 19 14:48:02 2017 +0000
@@ -18,6 +18,7 @@
     <!-- Use jQuery hosted from Google CDN -->
     <!--<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>-->
     <script type="text/javascript" src="js/jquery-2.1.4.js"></script>
+    <script type="text/javascript" src="js/resample.js"></script>
     <script type="text/javascript" src="js/loader.js"></script>
 </head>
 
--- a/js/core.js	Thu Jan 19 13:12:31 2017 +0000
+++ b/js/core.js	Thu Jan 19 14:48:02 2017 +0000
@@ -1507,6 +1507,22 @@
             function processAudio(response) {
                 var self = this;
                 return audioContext.decodeAudioData(response, function (decodedData) {
+                    if (decodedData.sampleRate !== audioContext.sampleRate) {
+                        // Resample
+                        var num_channels = decodedData.numberOfChannels,
+                            num_samples = decodedData.length,
+                            r = audioContext.sampleRate / decodedData.sampleRate,
+                            new_buffer = audioContext.createBuffer(num_channels, Math.floor(num_samples * r), audioContext.sampleRate),
+                            channel;
+                        for (channel = 0; channel < num_channels; channel++) {
+                            var buffer = new Float32Array(decodedData.length);
+                            decodedData.copyFromChannel(buffer, channel);
+                            buffer = xtract_resample(buffer, audioContext.sampleRate, decodedData.sampleRate);
+                            new_buffer.copyToChannel(buffer, channel);
+                        }
+                        decodedData = new_buffer;
+                        buffer = new_buffer = undefined;
+                    }
                     self.buffer = decodedData;
                     self.status = 2;
                     calculateLoudness(self, "I");
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/resample.js	Thu Jan 19 14:48:02 2017 +0000
@@ -0,0 +1,157 @@
+// Taken for JS-Xtract
+// https://github.com/nickjillings/js-xtract
+
+function xtract_resample(data, p, q, n) {
+    // Same function call as matlab:
+    // data is the array
+    // p is the target sample rate
+    // q is the source sample rate
+    // n is the desired filter order, n==1024 if undefined
+
+    function filter(N, c) {
+        var c_b, Re, Im, b;
+        c_b = Math.floor(c * N);
+        Re = new Float64Array(N);
+        Im = new Float64Array(N);
+        var i, j;
+        for (i = 0; i < c_b; i++) {
+            Re[i] = 1;
+        }
+        for (i = N - c_b + 1; i < N; i++) {
+            Re[i] = 1;
+        }
+        inverseTransform(Re, Im);
+        // Scale and shift into Im
+        for (i = 0; i < N; i++) {
+            j = (i + (N >> 1)) % N;
+            Im[i] = Re[j] / N;
+            // Apply compute blackman-harris to Im
+            var rad = (Math.PI * i) / (N);
+            Im[i] *= 0.35875 - 0.48829 * Math.cos(2 * rad) + 0.14128 * Math.cos(4 * rad) - 0.01168 * Math.cos(6 * rad);
+        }
+        return Im;
+    }
+
+    function polyn(data, K) {
+        var N = data.length;
+        var x = [0, data[0], data[1]];
+        var dst = new Float64Array(K);
+        var ratio = K / N;
+        var tinc = 1 / ratio;
+        var n = 0,
+            t = 0,
+            k;
+        for (k = 0; k < K; k++) {
+            if (t == n) {
+                // Points lie on same time
+                dst[k] = data[n];
+            } else {
+                var y = (t - n - 1) * (t - n) * x[0] - 2 * (t - n - 1) * (t - n + 1) * x[1] + (t - n) * (t - n + 1) * x[2];
+                dst[k] = y / 2;
+            }
+            t += tinc;
+            if (t >= n + 1) {
+                n = Math.floor(t);
+                x[0] = data[n - 1];
+                x[1] = data[n];
+                if (n + 1 < N) {
+                    x[2] = data[n + 1];
+                } else {
+                    x[2] = 0.0;
+                }
+            }
+        }
+        return dst;
+    }
+
+    function zp(a) {
+        var b = new Float64Array(a.length * 2);
+        for (var n = 0; n < a.length; n++) {
+            b[n] = a[n];
+        }
+        return b;
+    }
+
+    function overlap(X, b) {
+        var i, f;
+        var Y = new Float64Array(X.length);
+        var N = b.length;
+        var N2 = 2 * N;
+        var B = {
+            real: zp(b),
+            imag: new Float64Array(N * 2)
+        }
+        transform(B.real, B.imag);
+        var Xi = X.xtract_get_data_frames(N, N, false);
+        var Yi = Y.xtract_get_data_frames(N, N, false);
+        var x_last = new Float64Array(N);
+        var y_last = new Float64Array(N);
+        var w = new Float64Array(N2);
+        for (i = 0; i < N2; i++) {
+            var rad = (Math.PI * i) / (N2);
+            w[i] = 0.35875 - 0.48829 * Math.cos(2 * rad) + 0.14128 * Math.cos(4 * rad) - 0.01168 * Math.cos(6 * rad);
+        }
+        var xF = {
+            real: new Float64Array(N2),
+            imag: new Float64Array(N2)
+        }
+        var yF = {
+            real: new Float64Array(N2),
+            imag: new Float64Array(N2)
+        }
+        for (f = 0; f < Xi.length; f++) {
+            for (i = 0; i < N; i++) {
+                xF.real[i] = x_last[i] * w[i];
+                xF.real[i + N] = Xi[f][i] * w[i + N];
+                x_last[i] = Xi[f][i];
+                xF.imag[i] = 0;
+                xF.imag[i + N] = 0;
+            }
+            transform(xF.real, xF.imag);
+            for (i = 0; i < N2; i++) {
+                yF.real[i] = xF.real[i] * B.real[i] - xF.imag[i] * B.imag[i];
+                yF.imag[i] = xF.imag[i] * B.real[i] + xF.real[i] * B.imag[i];
+            }
+            transform(yF.imag, yF.real);
+            // Perform fft_shift and scale
+            for (i = 0; i < N; i++) {
+                var h = yF.real[i + N] / N;
+                yF.real[i + N] = yF.real[i] / N;
+                yF.real[i] = h;
+            }
+            for (i = 0; i < N; i++) {
+                Yi[f][i] = (yF.real[i] + y_last[i]);
+                y_last[i] = yF.real[i + N];
+            }
+        }
+        return Y;
+    }
+
+    // Determine which way to go
+    var b, N = data.length;
+    if (typeof n != "number" || n <= 0) {
+        n = 512;
+    }
+    if (p == q) {
+        return data;
+    }
+    var ratio = (p / q);
+    var K = Math.floor(N * ratio);
+    var dst;
+    if (p > q) {
+        // Upsampling
+        // 1. Expand Data range
+        dst = polyn(data, K);
+        // 2. Filter out spurious energy above q
+        var b = filter(n, 1 / ratio);
+        overlap(data, b);
+    } else {
+        // Downsampling
+        // 1. Filter out energy above p
+        var b = filter(n, ratio / 2);
+        var ds1 = overlap(data, b);
+        // 2. Decrease data range
+        dst = polyn(ds1, K);
+    }
+    return dst;
+}
--- a/test.html	Thu Jan 19 13:12:31 2017 +0000
+++ b/test.html	Thu Jan 19 14:48:02 2017 +0000
@@ -18,6 +18,7 @@
     <!-- Use jQuery hosted from Google CDN -->
     <!--<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>-->
     <script type="text/javascript" src="js/jquery-2.1.4.js"></script>
+    <script type="text/javascript" src="js/resample.js"></script>
     <script type="text/javascript" src="js/loader.js"></script>
 </head>