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diff --git a/files/zh-tw/web/api/analysernode/index.html b/files/zh-tw/web/api/analysernode/index.html new file mode 100644 index 0000000000..875993cea9 --- /dev/null +++ b/files/zh-tw/web/api/analysernode/index.html @@ -0,0 +1,226 @@ +--- +title: AnalyserNode +slug: Web/API/AnalyserNode +tags: + - API + - AnalyserNode + - Interface + - NeedsTranslation + - Reference + - TopicStub + - Web Audio API +translation_of: Web/API/AnalyserNode +--- +<p>{{APIRef("Web Audio API")}}</p> + +<p>The <strong><code>AnalyserNode</code></strong><strong> </strong>interface represents a node able to provide real-time frequency and time-domain analysis information. It is an {{domxref("AudioNode")}} that passes the audio stream unchanged from the input to the output, but allows you to take the generated data, process it, and create audio visualizations.</p> + +<p>An <code>AnalyzerNode</code> has exactly one input and one output. The node works even if the output is not connected.</p> + +<p><img alt="Without modifying the audio stream, the node allows to get the frequency and time-domain data associated to it, using a FFT." src="https://mdn.mozillademos.org/files/9707/WebAudioFFT.png" style="height: 174px; width: 661px;"></p> + +<table class="properties"> + <tbody> + <tr> + <th scope="row">Number of inputs</th> + <td><code>1</code></td> + </tr> + <tr> + <th scope="row">Number of outputs</th> + <td><code>1</code> (but may be left unconnected)</td> + </tr> + <tr> + <th scope="row">Channel count mode</th> + <td><code>"explicit"</code></td> + </tr> + <tr> + <th scope="row">Channel count</th> + <td><code>1</code></td> + </tr> + <tr> + <th scope="row">Channel interpretation</th> + <td><code>"speakers"</code></td> + </tr> + </tbody> +</table> + +<h2 id="Inheritance">Inheritance</h2> + +<p>This interface inherits from the following parent interfaces:</p> + +<p>{{InheritanceDiagram}}</p> + +<h2 id="Properties">Properties</h2> + +<p><em>Inherits properties from its parent, </em><em>{{domxref("AudioNode")}}</em>.</p> + +<dl> + <dt>{{domxref("AnalyserNode.fftSize")}}</dt> + <dd>Is an unsigned long value representing the size of the FFT (<a href="http://en.wikipedia.org/wiki/Fast_Fourier_transform" title="/en-US/docs/">Fast Fourier Transform</a>) to be used to determine the frequency domain.</dd> + <dt>{{domxref("AnalyserNode.frequencyBinCount")}} {{readonlyInline}}</dt> + <dd>Is an unsigned long value half that of the FFT size. This generally equates to the number of data values you will have to play with for the visualization.</dd> + <dt>{{domxref("AnalyserNode.minDecibels")}}</dt> + <dd>Is a double value representing the minimum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte values — basically, this specifies the minimum value for the range of results when using <code>getByteFrequencyData()</code>.</dd> + <dt>{{domxref("AnalyserNode.maxDecibels")}}</dt> + <dd>Is a double value representing the maximum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte values — basically, this specifies the maximum value for the range of results when using <code>getByteFrequencyData()</code>.</dd> + <dt>{{domxref("AnalyserNode.smoothingTimeConstant")}}</dt> + <dd>Is a double value representing the averaging constant with the last analysis frame — basically, it makes the transition between values over time smoother.</dd> +</dl> + +<h2 id="Methods">Methods</h2> + +<p><em>Inherits methods from its parent, </em><em>{{domxref("AudioNode")}}</em>.</p> + +<dl> + <dt>{{domxref("AnalyserNode.getFloatFrequencyData()")}}</dt> + <dd>Copies the current frequency data into a {{domxref("Float32Array")}} array passed into it.</dd> +</dl> + +<dl> + <dt>{{domxref("AnalyserNode.getByteFrequencyData()")}}</dt> + <dd>Copies the current frequency data into a {{domxref("Uint8Array")}} (unsigned byte array) passed into it.</dd> +</dl> + +<dl> + <dt>{{domxref("AnalyserNode.getFloatTimeDomainData()")}}</dt> + <dd>Copies the current waveform, or time-domain, data into a {{domxref("Float32Array")}} array passed into it.</dd> + <dt>{{domxref("AnalyserNode.getByteTimeDomainData()")}}</dt> + <dd>Copies the current waveform, or time-domain, data into a {{domxref("Uint8Array")}} (unsigned byte array) passed into it.</dd> +</dl> + +<h2 id="Examples">Examples</h2> + +<div class="note"> +<p><strong>Note</strong>: See the guide <a href="/en-US/docs/Web/API/Web_Audio_API/Visualizations_with_Web_Audio_API">Visualizations with Web Audio API</a> for more information on creating audio visualizations.</p> +</div> + +<h3 id="Basic_usage">Basic usage</h3> + +<p>The following example shows basic usage of an {{domxref("AudioContext")}} to create an <code>AnalyserNode</code>, then {{domxref("window.requestAnimationFrame()","requestAnimationFrame")}} and {{htmlelement("canvas")}} to collect time domain data repeatedly and draw an "oscilloscope style" output of the current audio input. For more complete applied examples/information, check out our <a href="http://mdn.github.io/voice-change-o-matic/">Voice-change-O-matic</a> demo (see <a href="https://github.com/mdn/voice-change-o-matic/blob/gh-pages/scripts/app.js#L128-L205">app.js lines 128–205</a> for relevant code).</p> + +<pre class="brush: js">var audioCtx = new (window.AudioContext || window.webkitAudioContext)(); +var analyser = audioCtx.createAnalyser(); + + ... + +analyser.fftSize = 2048; +var bufferLength = analyser.frequencyBinCount; +var dataArray = new Uint8Array(bufferLength); +analyser.getByteTimeDomainData(dataArray); + +// draw an oscilloscope of the current audio source + +function draw() { + + drawVisual = requestAnimationFrame(draw); + + analyser.getByteTimeDomainData(dataArray); + + canvasCtx.fillStyle = 'rgb(200, 200, 200)'; + canvasCtx.fillRect(0, 0, WIDTH, HEIGHT); + + canvasCtx.lineWidth = 2; + canvasCtx.strokeStyle = 'rgb(0, 0, 0)'; + + canvasCtx.beginPath(); + + var sliceWidth = WIDTH * 1.0 / bufferLength; + var x = 0; + + for(var i = 0; i < bufferLength; i++) { + + var v = dataArray[i] / 128.0; + var y = v * HEIGHT/2; + + if(i === 0) { + canvasCtx.moveTo(x, y); + } else { + canvasCtx.lineTo(x, y); + } + + x += sliceWidth; + } + + canvasCtx.lineTo(canvas.width, canvas.height/2); + canvasCtx.stroke(); + }; + + draw();</pre> + +<h2 id="Specifications">Specifications</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('Web Audio API', '#the-analysernode-interface', 'AnalyserNode')}}</td> + <td>{{Spec2('Web Audio API')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="Browser_compatibility">Browser compatibility</h2> + +<div>{{CompatibilityTable}}</div> + +<div id="compat-desktop"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Chrome</th> + <th>Firefox (Gecko)</th> + <th>Internet Explorer</th> + <th>Opera</th> + <th>Safari (WebKit)</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{CompatChrome(10.0)}}{{property_prefix("webkit")}}</td> + <td>{{CompatGeckoDesktop(25.0)}} </td> + <td>{{CompatNo}}</td> + <td>15.0 {{property_prefix("webkit")}}<br> + 22</td> + <td>6.0{{property_prefix("webkit")}}</td> + </tr> + </tbody> +</table> +</div> + +<div id="compat-mobile"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Android</th> + <th>Firefox Mobile (Gecko)</th> + <th>Firefox OS</th> + <th>IE Mobile</th> + <th>Opera Mobile</th> + <th>Safari Mobile</th> + <th>Chrome for Android</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{CompatUnknown}}</td> + <td>26.0</td> + <td>1.2</td> + <td>{{CompatUnknown}}</td> + <td>{{CompatUnknown}}</td> + <td>{{CompatUnknown}}</td> + <td>33.0</td> + </tr> + </tbody> +</table> +</div> + +<h2 id="See_also">See also</h2> + +<ul> + <li><a href="/en-US/docs/Web_Audio_API/Using_Web_Audio_API">Using the Web Audio API</a></li> +</ul> |