This object computes equalizer bi-quadratic filter coefficients and calculates the output of the input audio buffers processed through the filters that users specify.
It is an additional variant of the Parameter Biquad Audio Object specifically tailored for Harman Professional Audio use cases.
From SFD, the user can select what type of filtering to carry out via the “Biquad Topology field”:
- Direct Form I
- Direct Form II
- Transposed Direct Form II
This object operates in one of the two modes:
- Equalizer Mode – This mode generates a unique set of filters for every channel.
- Equalizer One Mode – This mode generates a single set of filters for all audio channels. The difference between this mode and Equalizer mode is that this mode generates a unique set of filters for all channels as opposed to one set per channel.
Equalizer modes support ramping functionality whenever filter type or parameters change at run-time.
Ramping variables are based on sampling rate, block length and ramp time. Implemented ramping strategy is based on first-order low-pass interpolation scheme.
In SFD, users can set the number of channels (the number of input and output channels is the same) as
well as the number of filters. Users can also select the object corresponding to the required mode.
The memory layout is exposed in GTT as (per filter): For each filter in each channel, the object exposes the following parameters for both tuning and state-tuning:
- Frequency (in Hz)
- Gain (in dB)
- Q-value
- Type of filter:
- Bypass
- All pass 1
- All pass 2
- High pass 1
- High pass 2
- Low pass 1
- Low pass 2
- High shelf 1
- High shelf 2
- Low shelf 1
- Low shelf 2
- Parameteric
- Bandpass
- Bandstop
- Amplifier
- Resonant
- Bell
- Low shelf variable-slope
- High shelf variable-slope
- Peaking GEQ
- Peaking HPro
- Low shelf HPro
- High shelf HPro
- Peaking AFS
- Peaking PA Plus
- Peaking Crown
- Low shelf PA Plus
- High shelf PA Plus
- Bypass (on/off)
- Width (in octaves- only for Bell filter)
- Asymmetry (on/ off- only for Bell filter)
- Slope (in dB per octave- only for variable-slope low/ high shelving filters)
This audio object is targeted at Professional Audio usage, specifically.