silenceRemover.coffee

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silenceRemover.coffee
¶
```
@chromaprint ?= {}
```
¶

Gets a function for removing silence from a buffer. It can be configured with a silence threshold. The window is also configurable (see the filter function below), but defaults to 55, which, I am told, is 5ms at 11025 Hz.
```
silenceRemover = (threshold, window = 55) ->
```
¶

The filter returns a function that returns true if the average ever passes above the threshold. The window is the starting point when summing up the bytes for the average.
```
  filter = (window) ->
    finished = false
    (byte, index) ->
      finished or= ((window += byte) / (index + 1)) > threshold
```
¶

This function returns what it’s given only if the average has s The returned function takes an array of bytes, only returns those that occur after the average has surpassed the silence threshold.
```
  (input) -> input.filter filter(window)

@chromaprint.silenceRemover = silenceRemover
```