Used with BASS_FXGetParameters and BASS_FXSetParameters to retrieve and set the parameters of a biquad filters effect.
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typedef struct{ |
Members
| lFilter | BASS_BFX_BQF_xxx filter types | One of the following filter
types:
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| fCenter | Cutoff (central) frequency in Hz | [1Hz..<info.freq/2] | ||||||||||||||||||
| fGain | Used only for PEAKINGEQ and Shelving filters in dB | [-15dB...0...+15dB] (can be above/below these limits) | ||||||||||||||||||
| fBandwidth | Bandwidth in octaves (fQ is not in use
(fBandwidth has a priority over fQ)) (between -3 dB frequencies for BANDPASS and NOTCH or between midpoint (fGgain/2) gain frequencies for PEAKINGEQ) |
[0.1...........<10] | ||||||||||||||||||
| fQ | The EE kinda definition (linear) (if fBandwidth is not in use) | [0.1.............1] | ||||||||||||||||||
| fS |
A "shelf slope" parameter (linear) (used only
with Shelving filters) when fS = 1, the shelf slope is as steep as you can get it and remain monotonically increasing or decreasing gain with frequency. |
[0.1.............1] | ||||||||||||||||||
| lChannel | The affected channels using BASS_BFX_CHANxxx flags |
Info:
BiQuad filters are second-order recursive linear
filters.
BASS_BFX_BQF_LOWPASS:
A low-pass
filter is a filter that passes low-frequency signals but attenuates
(reduces the amplitude of) signals with frequencies higher than the fCenter
frequency. The actual amount of attenuation for each frequency varies from
filter to filter. It is sometimes called a high-cut filter, or
treble cut filter when used in audio applications. A low-pass
filter is the opposite of a high-pass filter, and a band-pass filter is a
combination of a low-pass and a high-pass.
BASS_BFX_BQF_HIGHPASS:
A high-pass filter is
an LTI filter that passes high frequencies well but attenuates (i.e.,
reduces the amplitude of) frequencies lower than the fCenter frequency. The
actual amount of attenuation for each frequency is a design parameter of the
filter. It is sometimes called a low-cut filter; the terms bass-cut
filter or rumble filter are also used in audio applications.
BASS_BFX_BQF_BANDPASS:
A band-pass filter is a device that passes frequencies
within a certain range and rejects (attenuates) frequencies outside that range.
An example of an analogue electronic band-pass filter is an RLC circuit (a
resistor–inductor–capacitor circuit). These filters can also be created by
combining a low-pass filter with a high-pass filter.
BASS_BFX_BQF_NOTCH:
In signal processing, a band-stop filter or
band-rejection filter is a filter that passes most frequencies unaltered,
but attenuates those in a specific range to very low levels. It is the opposite
of a band-pass filter. A notch filter is a band-stop filter with a narrow
stopband (high Q factor). Notch filters are used in live sound reproduction
(Public Address systems, also known as PA systems) and in instrument amplifier
(especially amplifiers or preamplifiers for acoustic instruments such as
acoustic guitar, mandolin, bass instrument amplifier, etc.) to reduce or prevent
feedback, while having little noticeable effect on the rest of the frequency
spectrum. Other names include 'band limit filter', 'T-notch filter',
'band-elimination filter', and 'band-reject filter'.
BASS_BFX_BQF_ALLPASS:
An all-pass filter is a signal
processing filter that passes all frequencies equally, but changes the phase
relationship between various frequencies. It does this by varying its
propagation delay with frequency. Generally, the filter is described by the
frequency at which the phase shift crosses 90° (i.e., when the input and output
signals go into quadrature — when there is a quarter wavelength of delay between
them).
BASS_BFX_BQF_PEAKINGEQ:
A peaking equalizer raises or lowers a range of
frequencies around a central point in a bell shape. A peaking equalizer with
controls to adjust the level (fGain), fBandwidth (fQ) and center frequency (Hz)
is called a parametric equalizer.
Peaking Equalizer in BASS_FX can be achieved
directly and efficiently by BASS_FX_BFX_PEAKEQ
BASS_BFX_BQF_LOWSHELF:
A
low-shelf filter passes all
frequencies, but increasing or reducing frequencies below the fCenter frequency
by specified amount.
BASS_BFX_BQF_HIGHSHELF:
A
high-shelf filter passes all frequencies, but increasing or
reducing frequencies above the fCenter frequency by specified amount.
See also
BASS_ChannelSetFX