Add parametric equalizer and implement it for Arctis Nova 5

[ne0phyte]

Changes made

Added support for parametric equalizers.
Added implementation for Arctis Nova 5.

Description

I did not want to break the existing basic equalizer implementation so I added it independently as

• capability CAP_PARAMETRIC_EQUALIZER
• struct ParametricEqualizerInfo
• struct parametric_equalizer_settings
• struct parametric_equalizer_band
• enum EqualizerFilterType

I added YAML and JSON outputs, help texts, output of capabilities and the five filter types the Arctis Nova 5 supports for now.
More filter types can be added if other headsets feature different filters and the supported filters are set by each devices implementation.

I implemented the 10 band parametric equalizer for the Arctis Nova 5 and tested setting bands and the different filter types against the SteelSeries GG Windows software.

Bands are represented by the typical parameters of parametric equalizers: frequency, gain, q-factor (band width) and filter type.

This is the help text (which also gives an example of the format I chose to specify the bands):

Parametric Equalizer:
  --parametric-equalizer STRING         Set equalizer bands (bands separated by semicolon)
      Band format:                      FREQUENCY,GAIN,Q_FACTOR,FILTER_TYPE
      Availabe filter types:            lowshelf, lowpass, peaking, highpass, highshelf, 

      Examples: --parametric-equalizer  '300,3.5,1.5,peaking;14000,-2,1.414,highshelf'
                                        Sets a 300Hz +3.5dB Q1.5 peaking filter
                                        and a 14kHz -2dB Q1.414 highshelf filter

                --parametric-equalizer  reset
                                        Resets/disables all bands

This is the info the JSON (and YAML) output contains:

      "parametric_equalizer": {
        "bands": 10,
        "gain": {
            "step": 0.5,
            "min": -10,
            "max": 10,
            "base": 20
        },
        "q_factor": {
            "min": 0.2,
            "max": 10
        },
        "frequency": {
            "min": 20,
            "max": 20000
        },
        "filter_types": [
            "lowshelf",
            "lowpass",
            "peaking",
            "highpass",
            "highshelf",
        ]
      },

Headset Name

Arctis Nova 5

Checklist

• I adjusted the README (if needed)
• For new features in HeadsetControl: I discussed it beforehand in Issues or Discussions and adhered to the wiki