# Audio

## Play Audio

```javascript
const audio = new Audio('audio_file.mp3'); //or url
audio.play();
audio.pause();
```

```javascript
audio.currentTime;
audio.duration;
audioPlayer.addEventListener("timeupdate", () => {})
audioPlayer.addEventListener("ended", () => {});
```

## Record Audio

JS

```javascript
const stopButton = document.getElementById("stop");

const handleSuccess = function(stream) {
  console.log("Success");
  const options = { mimeType: "audio/webm" };
  const mediaRecorder = new MediaRecorder(stream, options);

  stopButton.onclick = () => {
    mediaRecorder.stop();
  };

  mediaRecorder.addEventListener("dataavailable", function(e) {
    if (e.data.size > 0) {
      console.log("Stopped", e);
      const audioURL = URL.createObjectURL(e.data);
      downloadLink.href = audioURL;
      downloadLink.download = "help.webm";
      if (window.URL) {
          player.srcObject = stream;
        } else {
             player.src = stream;
        }
    }
  });

  mediaRecorder.start();
};

navigator.mediaDevices
  .getUserMedia({ audio: true, video: false })
  .then(handleSuccess);
```

Html

```markup
<a id="download"> Download </a>
<button id="stop"> Stop </button>
<audio id="player" controls></audio>
```

## Audio Viz

```javascript
const VIZ_SENSITIVITY = 150;

useEffect(() => {
  let analyser; //"global"

  function update() {
    // Schedule the next update
    if (analyser) {
      requestAnimationFrame(update);

      const frequencyData = new Uint8Array(analyser.frequencyBinCount);
      const els = document.querySelectorAll(".audio_bar");
      // Get the new frequency data
      analyser.getByteFrequencyData(frequencyData);
            const average = frequencyData.reduce((acc, e) => acc + e / frequencyData.length, 0);
      const newPercent = (average / 255) * VIZ_SENSITIVITY;
      els[0].style.height = Math.min(newPercent, 100) + "%";
    }
  }

  if (audioStream) {
    console.log("Creating contexts");
    const audioCtx = new AudioContext();
    const source = audioCtx.createMediaStreamSource(audioStream);
    analyser = audioCtx.createAnalyser();
    source.connect(analyser);
    analyser.fftSize = 2048;
    // analyser.connect(audioCtx.destination);
    update();
    return () => (analyser = null);
  }
}, [audioStream, recordingState]);
```

## Audio Context

Analyze and create and play audio

Create, manipulate, and play audio

If you dont want to play it, use [`OfflineAudioContext`](https://developer.mozilla.org/en-US/docs/Web/API/OfflineAudioContext).

```javascript
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
const sine = audioCtx.createOscillator();
sine.start();
sine.connect(audioCtx.destination);
```

1. Create the audio context.
2. Inside the context, create sources — such as [\`\`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/audio), oscillator, or stream.
3. Create effects nodes, such as reverb, biquad filter, panner, or compressor.
4. Choose the final destination for the audio, such as the user's computer speakers.
5. Establish connections from the audio sources through zero or more effects, eventually ending at the chosen destination.

### Edge Cases

Chrome needs use interaction before creating an audio context ot it


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