31:[] 2f:{"title":"Meyda - Audio feature extraction for JavaScript.","cells":[{"id":0,"value":"md`# Meyda - Audio feature extraction for JavaScript.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":292,"value":"md`### Demo using Meyda to map audio RMS levels to slider`","pinned":false,"hidden":false,"mode":"ojs"},{"id":268,"value":"md`\n[This notebook is the observablehq implementation of the Meyda 'online-web-audio' example](https://meyda.js.org/guides/online-web-audio)\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":271,"value":"md`## Start by selecting an audio file:`","pinned":false,"hidden":false,"mode":"ojs"},{"id":2,"value":"viewof file = html``","pinned":false,"hidden":false,"mode":"ojs"},{"id":42,"value":"viewof audioHTML = html`\n \n \n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":120,"value":"viewof startButton = {\n //https://beta.observablehq.com/@mbostock/wait-until-button\n const form = html``;\n form.button.onclick = event => {\n event.preventDefault();\n start(); \n };\n return form;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":86,"value":"slider = html`\n\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":102,"value":"viewof stopButton = {\n //https://beta.observablehq.com/@mbostock/wait-until-button\n const form = html``;\n form.button.onclick = event => {\n event.preventDefault();\n stop();\n };\n return form;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":136,"value":"md`## Declarations`","pinned":false,"hidden":false,"mode":"ojs"},{"id":183,"value":"isInitialized = !!analyzer;","pinned":false,"hidden":false,"mode":"ojs"},{"id":207,"value":"analyzer = initialize(fileDataUri);","pinned":true,"hidden":false,"mode":"ojs"},{"id":230,"value":"function initialize() {\n if (!fileDataUri) {\n return null; \n }\n \n const audioContext = new AudioContext()\n const htmlAudioElement = document.getElementById(\"audio\");\n const source = audioContext.createMediaElementSource(htmlAudioElement);\n\n source.connect(audioContext.destination);\n\n const levelRangeElement = slider;\n \n const analyzer = meyda.createMeydaAnalyzer({\n \"audioContext\": audioContext,\n \"source\": source,\n \"bufferSize\": 512,\n \"featureExtractors\": [\"rms\"],\n \"callback\": features => {\n levelRangeElement.value = features.rms;\n }\n });\n \n analyzer.start();\n \n return analyzer;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":83,"value":"function start() {\n if (isInitialized) {\n analyzer.start(); \n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":99,"value":"function stop() {\n if (isInitialized) {\n analyzer.stop(); \n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":88,"value":"levelRangeElement = slider;\n","pinned":false,"hidden":false,"mode":"ojs"},{"id":211,"value":"fileDataUri = URL.createObjectURL(file);","pinned":false,"hidden":false,"mode":"ojs"},{"id":57,"value":"md`## Imports`","pinned":false,"hidden":false,"mode":"ojs"},{"id":58,"value":"meyda = require(\"meyda\")","pinned":false,"hidden":false,"mode":"ojs"}],"files":"$W31","stdlib":"1","titling":"auto"}