lessons-leant.txt

# Audio

Sound comes in periodic waves
periodicity is perceived as pitch
Pitch is meassured in frequency (number of times the wave pattern repeats every second) in hertz
double the wave (higher freq) -> same note, pitch an octave higher
half the wave (lower freq) -> same note, pitch an octave lower

Octaves are split in 12 semitones
Detune is measured in cents, an octave consisting of 1200 cents, each semitone of 100 cents
Detune of 1200 is an ocatve higher, -1200 lower

```
function playNote(semitones) {
  // Assume a new source was created from a buffer.
  var semitoneRatio = Math.pow(2, 1/12);
  source.playbackRate.value = Math.pow(semitoneRatio, semitones);
  source.start(0);
}

function playNote(semitones) {
  // Assume a new source was created from a buffer.
  var semitoneRatio = Math.pow(2, 1/12);
  source.playbackRate.value = Math.pow(semitoneRatio, semitones);
  source.start(0);
}
```


Autocorrelation is comparing a soundwave to itself. When it repeats itself you get the fequency and thus the note
getFloatTimeDomainData populates an array with floating point wave data with values ranging between -1 and 1.

The fftSize property on the AnalyserNode is used to determine how much data you get



# Loading Audio data
arraybuffer is a data type that still needs to be put into a format the browser understands

decodeAudioData does just that

the loaded song becomes a browser readable AudioBufferSourceNdoe

You play sounds from a BufferSource

An AudioBuffer takes as its parameters a number of channels (1 for mono, 2 for stereo, etc), a length, meaning the number of sample frames inside the buffer, and a sample rate, which is the number of sample frames played per second.

# Visualizing Data

frequency data vs time domain data

time domain, time is x-axis
freq domain, freq is x-axis in hz

get[...]Data only for a certain point in time

so draw a graph in the beginning for the whole
then draw real time input on top of it

### page visibility data


# Live Audio input

getUserMedia