Sound Bytes

A coding competition

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Song of Thrones

by Ken Gros

Listen

Editor’s Note: This entry produces audio output directly as well as a file. The audio file must then be manually converted to ogg / pcm and the resulting file produced does not exactly match the original. For technical reasons, only the converted audio file can be shown here.

Readers are encouraged to run the original for themselves, but your mileage may vary.

Song of Thrones

A minimal sound generating coding challange

Challange Accepted

Technique

Step 1

The body tag is created and a button is placed inside with a click event attached.

Step 2

When the button is clicked an async function calls a secondary function that will return a promise to the primary.

Step 3

The secondary function accepts 3 variables frequency, wave shape and duration from an array of notes.

• First: it creates the AudioContext, Oscillator and Gain which are required to hear sound.
• Second: it connects the MediaStream to the Destination which are required play the sound over the device’s speakers
• Third: it creates a MediaRecorder which is required to capture and store each sound so that it can be written to a file and downloaded.
• Fourth: it starts the MediaRecorder and the Oscillator and after the specified duration pushes the chunk of data to an array.
• Fifth: the secondary function completes and the promise to the primary is fulfilled, the primary function resumes
  
  The array of notes is built with the above function.

Step 4

In the next phase of the primary function the chunks of audio are combined with Blob and encoded. Once this step is complete the url of the encoded media is assigned to an <a> tag and a click event is fired on it starting the download of the file.

** All images show non-minified code for readability **

Golf Score

How To

• Navigate to a.html
• Open with Chrome browser
• Press play button
• Once the audio has finished playing the app will create an automatic download in .webm format
• Navigate to the Downloads folder on your local disk
• Locate _.webm
• Open _.webm with Chrome browser
• Enjoy the audio again

Language

Chrome (JavaScript + WebAPI)

Golf Score

989

Parameters

Sample Rate:	Hz
Sample Size:	bits
Channels:
Encoding:

Spectrogram