Google Flix Engine Linux Reference Manual - Manual (Page 122)

116 Flix Engine Linux Module Documentation
5.29 Lowpass
5.29.1 Detailed Description
The lowpass audio filter is a filter to attenuate sounds in the audio track that are higher than the cutoff
frequency. In other words, low frequencies are passed by the filter, and high frequencies are stopped.
Example Usage:
sc = Flix2_AddFilter(&filter, flix, FE2_FILTER_LOWPASS);
// Cut off frequencies above 10khz
if(sc == ON2_OK)
sc = Flix2_FilterSetParam(filter, FE2_LOWPASS_CUTOFF, 10000.0);
Additional References:
Cookbook formulae for audio EQ biquad filter coefficients by Robert
Bristow-Johnson
Defines
• #define FE2_FILTER_LOWPASS
Filter name for use with Flix2_AddFilter() .
• #define FE2_LOWPASS_Q
Filter parameter for shape constant ("Q" coefficient).
• #define FE2_LOWPASS_CUTOFF
Filter parameter for cutoff frequency.
5.29.2 Define Documentation
5.29.2.1 #define FE2_FILTER_LOWPASS
Filter name for use with Flix2_AddFilter() .
Definition at line 46 of file lowpass.h.
5.29.2.2 #define FE2_LOWPASS_CUTOFF
Filter parameter for cutoff frequency.
This is the filter’s "corner" frequency. Components of the sound track with frequencies higher than this
frequency will be attenuated. If very precise control of the cutoff frequency is required, note that the
response of the filter at this frequency is -3db. Note that the maximum frequency is always half of the sam-
pling rate of the produced file (5512.5/11025/22050 for sample rates
Hertz11025 / Hertz22050 / Hertz44100
respectively).
Definition at line 69 of file lowpass.h.
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