{"id":763,"date":"2017-01-11T23:53:00","date_gmt":"2017-01-11T15:53:00","guid":{"rendered":"https:\/\/ntzyz.io\/?p=763"},"modified":"2017-09-18T19:33:40","modified_gmt":"2017-09-18T11:33:40","slug":"html-audiocontext-01-2","status":"publish","type":"post","link":"https:\/\/archive.ntzyz.io\/2017\/01\/11\/html-audiocontext-01-2\/","title":{"rendered":"[HTML] AudioContext \u6298\u817e\u7b14\u8bb0 02"},"content":{"rendered":"<style> p.indent { text-indent: 2em; } <\/style>\n<p class=\"indent\">\u4e4b\u524d\u6211\u4eec\u5df2\u7ecf\u770b\u5230\u4e86\u5982\u4f55\u5229\u7528 HTML \u7684 WebAudio API \u64ad\u653e\u4e00\u6bb5\u81ea\u5b9a\u4e49\u7684\u97f3\u9891\uff0c\u5176\u5b9e\u96be\u5ea6\u5e76\u4e0d\u5927\uff0c\u4e3b\u8981\u6b65\u9aa4\u5c31\u662f\u521b\u5efa\u97f3\u9891\u4e0a\u4e0b\u6587\uff0c\u521b\u5efa\u7f13\u51b2\u533a\u548c\u97f3\u9891\u6e90\uff0c\u4e4b\u540e\u5728\u7f13\u5b58\u533a\u5185\u66b4\u529b\u5199\u5165\u6ce2\u5f62\u6570\u636e\uff0c\u5c31\u53ef\u4ee5\u64ad\u653e\u4e86\u3002<\/p>\n<p class=\"indent\">\u6709\u4e86\u8fd9\u4e9b\u529f\u80fd\uff0c\u7406\u8bba\u4e0a\u6211\u4eec\u662f\u53ef\u4ee5\u5728\u6d4f\u89c8\u5668\u91cc\u4f7f\u7528 JavaScript \u89e3\u7801\u4efb\u610f\u7684\u97f3\u9891\u6587\u4ef6\u5e76\u64ad\u653e\u7684\uff0c\u7136\u800c\u5b9e\u9645\u4e0a JavaScript \u672c\u8eab\u7b97\u662f\u4e2a\u534a\u6b8b\u5e9f\u8bed\u8a00\uff0c\u800c\u4e14\u65e2\u7136\u80fd\u7528 HTMLAudio \u6807\u7b7e\u6765\u64ad\u653e\u97f3\u9891\uff0c\u4e3a\u4ec0\u4e48\u8981\u81ea\u5df1\u89e3\u7801\u5462\uff08<\/p>\n<p class=\"indent\">\u4e0d\u8fc7\u8bdd\u8bf4\u56de\u6765\uff0c\u4e0d\u662f\u6240\u6709\u4ee3\u7801\u90fd\u662f\u5199\u4e86\u62ff\u53bb\u7528\u7684\uff0c\u6709\u7684\u65f6\u5019\u6298\u817e\u6298\u817e\u4e00\u4e9b\u6bd4\u8f83\u5947\u602a\u7684\u4e1c\u897f\u4e5f\u975e\u5e38\u6709\u8da3\u3002\u60f3\u5230\u4e16\u754c\u4e0a\u6709\u4e00\u4e2a\u53eb WAV(audio\/x-wave) \u7684\u97f3\u9891\u683c\u5f0f\uff0c\u5176\u7ed3\u6784\u542c\u8bf4\u4e5f\u662f\u975e\u5e38\u7684\u7b80\u5355\u7c97\u66b4\uff0c\u5728\u89e3\u7801\u4e0a\u57fa\u672c\u6ca1\u6709\u4ec0\u4e48\u590d\u6742\u5ea6\u3002\u4e8e\u662f\u4e3a\u4ec0\u4e48\u4e0d\u5c1d\u8bd5\u7740\u81ea\u5df1\u7528 JavaScript \u628a wav \u97f3\u9891\u901a\u8fc7\u97f3\u9891\u4e0a\u4e0b\u6587\u63a5\u53e3\u64ad\u653e\u51fa\u6765\u5462\uff1f<\/p>\n<p><!--more--><\/p>\n<h2>\u97f3\u9891\u6587\u4ef6\u7684\u52a0\u8f7d\u548c\u5206\u6790<\/h2>\n<p class=\"indent\">\u8fd9\u4e00\u6bb5\u5176\u5b9e\u6ca1\u4ec0\u4e48\u597d\u8bf4\u7684\uff0c\u8d70 XMLHttpRequest \u8bf7\u6c42\u4e00\u4e2a ArrayBuffer \u57fa\u672c\u5c31\u53ef\u4ee5\u4e86\uff0c\u503c\u5f97\u6ce8\u610f\u7684\u662f\u9700\u8981\u89e3\u51b3\u8de8\u57df\u95ee\u9898\uff08\u5982\u679c\u5a92\u4f53\u6587\u4ef6\u548c\u5f53\u524d URL \u4e0d\u5728\u540c\u4e00\u57df\u4e0b\uff09\u3002\u4e0d\u8fc7\u65e2\u7136 Google Chrome \u5df2\u7ecf\u652f\u6301 Promise \u4e86\uff0c\u5c31\u8bd5\u8bd5\u8d70 Promise \u6765\u5c01\u88c5\u4e00\u4e2a HTTP \u5ba2\u6237\u7aef\u5427\uff08x<\/p>\n<pre class=\"lang:javascript\">  function $get(url) {\r\n    return new Promise((resolve, reject) => {\r\n      let xhr = new XMLHttpRequest();\r\n      xhr.open('GET', url);\r\n      xhr.responseType = 'arraybuffer';\r\n      xhr.addEventListener('progress', (e) => {\r\n        status.innerText = `Loading media ${(100 * e.loaded \/ e.total).toFixed(3)}% ...`;\r\n      });\r\n      xhr.onreadystatechange = () => {\r\n        switch(xhr.readyState) {\r\n        case xhr.DONE:\r\n          resolve(xhr.response)\r\n          break;\r\n        default:\r\n          break;\r\n        }\r\n      };\r\n      xhr.send();\r\n    });\r\n  }<\/pre>\n<p class=\"indent\">\u4ee3\u7801\u91cc\u7684 status \u662f\u4e00\u4e2a span\uff0c\u7528\u6765\u5b9e\u65f6\u663e\u793a xhr \u7684\u52a0\u8f7d\u8fdb\u5ea6\u7684\uff0c\u6bd5\u7adf wav \u8fd9\u4e48\u5927\u2026\u2026<\/p>\n<p class=\"indent\">\u4e4b\u540e\u7684\u4ee3\u7801\u91cc\u53ea\u8981\u4f7f\u7528 $get(url).then(callback) \u8fd9\u6837\u7684\u5f62\u5f0f\u5c31\u53ef\u4ee5\u52a0\u8f7d wav \u6587\u4ef6\u4e86\u3002<\/p>\n<h2>wav \u6587\u4ef6\u683c\u5f0f<\/h2>\n<p class=\"indent\">\u55ef\u641e\u5230\u6587\u4ef6\u4e4b\u540e\u5c31\u5f97\u5f00\u59cb\u89e3\u7801\u4e86\uff0c\u5728\u89e3\u7801\u4e4b\u524d\uff0c\u5fc5\u987b\u5148\u83b7\u5f97\u4e00\u4e9b\u5143\u6570\u636e\u4f8b\u5982\u91c7\u6837\u7387\u554a\u6587\u4ef6\u5927\u5c0f\u58f0\u9053\u6570\u4ec0\u4e48\u7684\u3002<\/p>\n<p class=\"indent\">wav \u683c\u5f0f\u672c\u8eab\u662f\u5f88\u7b80\u5355\u7684\uff0c\u9996\u5148\u5f97\u4ecb\u7ecd\u4e00\u4e0b wav \u6587\u4ef6\u91cc\u7684\u6574\u4f53\u63cf\u8ff0\u5355\u4f4d\uff1aChunk\uff0c\u5176\u7ed3\u6784\u5982\u4e0b<\/p>\n<pre class=\"lang:c\">\r\nstruct wavChunk {\r\n  unsigned char chunkName[4];\r\n  unsigned int  chunkSize;\r\n  unsigned char chunkData[];  \/\/ sizeof is chunkSize\r\n}\r\n<\/pre>\n<p class=\"indent\">\u77e5\u9053\u4e86 Chunk \u4e4b\u540e\uff0c\u5269\u4e0b\u7684\u5c31\u5f88\u597d\u89e3\u91ca\u4e86\uff1awav \u6587\u4ef6\u672c\u8eab\u5c31\u662f\u4e00\u4e2a\u540d\u4e3a RIFF \u7684 Chunk\uff0c\u968f\u540e\u5305\u542b\u82e5\u5e72 Chunk \u6765\u8868\u793a\u4e00\u4e9b\u5143\u6570\u636e\uff0c\u6bd4\u5982 FMT Chunk \u4e2d\u63cf\u8ff0\u4e86\u97f3\u9891\u683c\u5f0f\u3001\u58f0\u9053\u6570\u3001\u91c7\u6837\u7387\u3001\u91c7\u6837\u4f4d\u6570\uff0c\u800c data Chunk \u4e2d\u5c31\u662f\u97f3\u9891\u7684 PCM \u6570\u636e\u3002\u521a\u624d\u63d0\u5230\u7684\u4e09\u4e2a Chunk \u7684\u7ed3\u6784\u90fd\u662f\u56fa\u5b9a\u7684\uff0c\u5269\u4e0b\u4e00\u4e9b\u6bd4\u5982 LIST \u4e4b\u7c7b\u7684 Chunk \u6211\u4eec\u53ef\u4ee5\u6682\u65f6\u5148\u4e0d\u7ba1\u3002<\/p>\n<p class=\"indent\">\u4e8e\u662f\uff0c\u4e00\u4e9b\u5206\u6790\u524d\u7684\u51c6\u5907\uff1a<\/p>\n<pre class=\"lang:javascript\">\r\n      let rawFile = file;\r\n      file = new Uint8Array(rawFile);\r\n\r\n      \/\/ Reference for RIFF chunk and FMT chunk\r\n      let RIFF = {\r\n        RIFF:           { begin:    0, length:    4, type: 'CHAR'},\r\n        ChunkSize:      { begin:    4, length:    4, type: 'INTEGER'},\r\n        WAVE:           { begin:    8, length:    4, type: 'CHAR'},\r\n      }\r\n      let FMT = {\r\n        fmt:            { begin:   12, length:    4, type: 'CHAR'},\r\n        Subchunk1Size:  { begin:   16, length:    2, type: 'INTEGER'},\r\n        AudioFormat:    { begin:   20, length:    2, type: 'INTEGER'},\r\n        NumOfChan:      { begin:   22, length:    2, type: 'INTEGER'},\r\n        SamplesPerSec:  { begin:   24, length:    4, type: 'INTEGER'},\r\n        bytesPerSec:    { begin:   28, length:    4, type: 'INTEGER'},\r\n        blockAlign:     { begin:   32, length:    2, type: 'INTEGER'},\r\n        bitsPerSample:  { begin:   34, length:    2, type: 'INTEGER'},\r\n      }\r\n      \r\n      file.subArray = (begin, length) => {\r\n        return file.slice(begin, begin + length);\r\n      };\r\n\r\n      let readChar = (begin, length) => Array\r\n        .from(file\r\n          .subArray(begin, length))\r\n        .map(ch => String.fromCharCode(ch))\r\n        .join('');\r\n\r\n      let readInt = (begin, length) => Array\r\n        .from(file\r\n          .subArray(begin, length))\r\n        .reverse()\r\n        .reduce((a, b) => a * 256 + b);\r\n\r\n      let readChunk = (ref, save) => {\r\n        for (let item in ref) {\r\n          switch(ref[item].type) {\r\n            case 'CHAR':\r\n              save[item] = readChar(ref[item].begin, ref[item].length);\r\n              break;\r\n            case 'INTEGER':\r\n              save[item] = readInt(ref[item].begin, ref[item].length);\r\n              break;\r\n          }\r\n        }\r\n      }<\/pre>\n<p class=\"indent\">\u7b80\u5355\u7684\u63cf\u8ff0\u4e00\u4e0b\u5427\uff0c\u7531\u4e8e JavaScript \u8fd9\u4e2a\u7834\u70c2\u8bed\u8a00\u6570\u636e\u7c7b\u578b\u6b8b\u7f3a\uff0c\u5bf9\u4e8e uint32_t \u7c7b\u7684\u6570\u5b57\u6211\u4eec\u9700\u8981\u81ea\u5df1\u51c6\u5907\u529e\u6cd5\u8bfb\u53d6\uff0c\u8fd8\u597d\u8fd9\u662f\u4e00\u4e2a\u65e0\u7b26\u53f7\u6574\u6570\uff0c\u53ea\u8981\u770b\u4e0b\u5c0f\u7aef\u7684\u5b9a\u4e49\u5c31\u80fd\u8f7b\u677e\u7684\u5c06\u5176\u8f6c\u6362\u4e3a\u5177\u4f53\u7684\u6570\u636e\u3002\u4e0a\u9762\u4ee3\u7801\u4e2d\u7684 readInt \u5c31\u80fd\u5b8c\u6210\u8fd9\u9879\u9700\u6c42\u3002<\/p>\n<p class=\"indent\">\u63a5\u4e0b\u6765\u7ee7\u7eed\uff0c\u5f00\u59cb\u8bfb\u53d6 RIFF Chunk\uff1a<\/p>\n<pre class=\"lang:javascript\">      \/\/ Read the RIFF chunk\r\n      readChunk(RIFF, this);<\/pre>\n<p class=\"indent\">\u8fd9\u53e5\u6ca1\u4ec0\u4e48\u597d\u8bf4\u7684\uff0c\u6309\u7167\u4e4b\u524d\u5b9a\u4e49\u7684 RIFF \u53d8\u91cf\uff0c\u6309\u683c\u5f0f\u8bfb\u53d6\u6570\u636e\u3002\u7136\u540e\u4f9d\u6b21\u8bfb\u53d6\u63a5\u4e0b\u6765\u7684 Chunk\uff0c\u76f4\u5230\u8bfb\u5230 data Chunk\u3002\u5176\u4e2d\uff0c\u5982\u679c\u9047\u5230 FMT Chunk \u5c31\u9700\u8981\u6309\u683c\u5f0f\u8bfb\u53d6\uff0c\u5269\u4e0b\u7684\u5c31\u6682\u65f6\u5148\u4e0d\u7ba1\u4e86\u5427\u3002<\/p>\n<pre class=\"lang:javascript\">      for (let offset = 12;;) {\r\n        let chunkName = readChar(offset, 4); offset += 4;\r\n        let chunkSize = readInt(offset, 4); offset += 4;\r\n        this[chunkName] = {};\r\n        this[chunkName].size = chunkSize;\r\n        if (chunkName === 'fmt ') {\r\n          \/\/ Read the RIFF chunk\r\n          readChunk(FMT, this[chunkName]);\r\n        }\r\n        else {\r\n          if (chunkName == 'data') {\r\n            let type = `Int${this['fmt '].bitsPerSample}Array`;\r\n            this[chunkName] = new window[type](rawFile.slice(offset, chunkSize))\r\n            break;\r\n          }\r\n          \/\/ Read as raw\r\n          this[chunkName]._rawData = file.subArray(offset, chunkSize);\r\n        }\r\n        offset += chunkSize;\r\n      }<\/pre>\n<p class=\"indent\">\u5c06\u4ee5\u4e0a\u90e8\u5206\u653e\u5230 Wav \u7c7b\u7684\u6784\u9020\u51fd\u6570\u4e2d\u53bb\uff0c\u6784\u9020\u5b8c\u6bd5\u540e\uff0c\u6211\u4eec\u80fd\u5f97\u5230\u8fd9\u6837\u7684\u4e00\u4e2a\u5bf9\u8c61\uff1a<\/p>\n<pre>\r\nWav {\r\n ChunkSize: 20045138,\r\n LIST: { ... },\r\n RIFF: 'RIFF',\r\n WAVE: 'WAVE',\r\n data: Int16Array[...],\r\n \"fmt \": Object,\r\n}\r\n<\/pre>\n<p class=\"indent\">\u5173\u952e\u6570\u636e\u5c31\u5728 fmt \u548c data \u91cc\u4e86\uff1afmt \u5b9a\u4e49\u4e86\u5982\u4f55\u53bb\u64ad\u653e\uff0cdata \u5219\u662f\u5f85\u64ad\u653e\u7684\u5185\u5bb9\u3002<\/p>\n<h2>\u521d\u59cb\u5316 AudioContext \u548c\u5176\u4ed6\u76f8\u5173\u53d8\u91cf<\/h2>\n<p class=\"indent\">\u8fd9\u91cc\u8fd8\u662f\u6bd4\u8f83\u7b80\u5355\u7684\uff0c\u5c06 fmt \u533a\u5757\u91cc\u7684\u6570\u636e\u62ff\u51fa\u6765\u5c31\u53ef\u4ee5\u4e86\uff0c\u5185\u5bb9\u53ef\u4ee5\u53c2\u8003\u4e0a\u4e00\u7bc7\u7b14\u8bb0\uff1a<\/p>\n<pre class=\"lang:javascript\">\r\n      let ctx = this.ctx = new AudioContext();\r\n      let framesCount = this.framesCount = wav.ChunkSize \/ (wav['fmt '].bitsPerSample \/ 8);\r\n\r\n      let audioBuffer = this.audioBuffer = ctx.createBuffer(\r\n        wav['fmt '].NumOfChan, \r\n        framesCount \/ 2, \r\n        wav['fmt '].SamplesPerSec\r\n      );\r\n\r\n      this.source = ctx.createBufferSource();\r\n      this.source.loop = false;\r\n      this.source.connect(ctx.destination);\r\n      this.source.buffer = this.audioBuffer;\r\n<\/pre>\n<p class=\"indent\">\u8fd9\u91cc\u9762\u5c11\u4e86\u4e00\u6b65\uff1aPCM \u6570\u636e\u7684\u586b\u5165\u3002\u6211\u662f\u60f3\u7740\u8ba9\u97f3\u9891\u4e00\u8fb9\u64ad\u653e\u4e00\u8fb9\u586b\u5165\u7684\uff0c\u53ef\u60dc\u8fd9\u6837\u4e0b\u6765\u53ea\u6709 Chrome \u7cfb\u6d4f\u89c8\u5668\u80fd\u6b63\u5e38\u64ad\u653e\u4e86\uff09<\/p>\n<p class=\"indent\">\u8fb9\u64ad\u653e\u8fb9\u586b\u5165\u672c\u8eab\u662f\u53ef\u4ee5\u7528 setInterval \u5b9e\u73b0\uff0c\u987a\u4fbf\u8d81\u673a\u957f\u8bd5\u4e00\u6ce2 ES6 \u7684 yield \u5173\u952e\u5b57\uff1a<\/p>\n<pre class=\"lang:javascript\">\r\n    *step() {\r\n      let ctx = this.ctx;\r\n      let channelBuffering = [];\r\n      for (let i = 0; i < wav['fmt '].NumOfChan; ++i) {\r\n        channelBuffering[i] = this.audioBuffer.getChannelData(i);\r\n      }\r\n\r\n      for (let currentFrame = 0; currentFrame < this.framesCount; ++currentFrame) {\r\n        channelBuffering[currentFrame % 2][Math.ceil(currentFrame \/ 2)]\r\n          = Number(wav.data[currentFrame]) \/ (1 << (wav['fmt '].bitsPerSample - 1));\r\n\r\n        if (!this.started) {\r\n          setTimeout(() => {this.source.start()}, 10);\r\n          this.started = true;\r\n        }\r\n\r\n        yield currentFrame;\r\n      }\r\n    }\r\n<\/pre>\n<p class=\"indent\">\u5c06\u4ee5\u4e0a\u51fd\u6570\u90fd\u603c\u5230 class Wav \u4e2d\u540e\uff0c\u53ea\u8981\u5728\u51c6\u5907\u4e00\u4e2a\u4e3b\u51fd\u6570\u5c31\u53ef\u4ee5\u5b8c\u6210 wav \u7684\u89e3\u7801\u548c\u64ad\u653e\u4e86\u3002\u5177\u4f53\u4ee3\u7801\u7684\u8bdd\u5c31\u4e0d\u8d34\u4e86\uff0c\u6ca1\u4ec0\u4e48\u597d\u8ba8\u8bba\u7684\u4e86\uff08\u9003<\/p>\n<p class=\"indent\">\u6700\u540e\u9644\u4e0a\u4e00\u4e2a\u8fd0\u884c\u6548\u679c\uff1a<a href=\"https:\/\/ntzyz.github.io\/playground\/wav-decode\/\" target=\"_blank\">playground\/wav-decode<\/a>\u548c<a href=\"https:\/\/github.com\/ntzyz\/playground\/blob\/master\/wav-decode\/main.js\" target=\"_blank\">\u5b8c\u6574\u6e90\u4ee3\u7801<\/a>\uff0c\u5176\u4e2d\u8fd8\u52a0\u4e86\u70b9\u53ef\u89c6\u5316\u7684\u9b54\u6cd5\uff0cwav \u7684\u4f53\u79ef\u771f\u7684\u662f\u69fd\u70b9\uff08<\/p>\n<h2>\u53c2\u8003\u94fe\u63a5<\/h2>\n<ol type=\"1\">\n<li><a href=\"http:\/\/soundfile.sapp.org\/doc\/WaveFormat\/\" target=\"_blank\">WAVE PCM soundfile format<\/a><\/li>\n<li><a href=\"https:\/\/en.wikipedia.org\/wiki\/WAV\" target=\"_blank\">WAV &#8211; Wikipedia<\/a><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>\u4e4b\u524d\u6211\u4eec\u5df2\u7ecf\u770b\u5230\u4e86\u5982\u4f55\u5229\u7528 HTML \u7684 WebAudio API \u64ad\u653e\u4e00\u6bb5\u81ea\u5b9a\u4e49\u7684\u97f3\u9891\uff0c\u5176\u5b9e\u96be\u5ea6\u5e76\u4e0d\u5927\uff0c\u4e3b\u8981 &hellip; <a href=\"https:\/\/archive.ntzyz.io\/2017\/01\/11\/html-audiocontext-01-2\/\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">[HTML] AudioContext \u6298\u817e\u7b14\u8bb0 02<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[43,42,57,58],"_links":{"self":[{"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/posts\/763"}],"collection":[{"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/comments?post=763"}],"version-history":[{"count":11,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/posts\/763\/revisions"}],"predecessor-version":[{"id":900,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/posts\/763\/revisions\/900"}],"wp:attachment":[{"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/media?parent=763"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/categories?post=763"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/archive.ntzyz.io\/wp-json\/wp\/v2\/tags?post=763"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}