Miles Sound System SDK 7.2a

AIL_set_sample_low_pass_cut_off

The function AIL_set_sample_low_pass_cut_off applies a low-pass filter to the digital audio sample.

void AIL_set_sample_low_pass_cut_off(
  HSAMPLE sample,
  F32 cut_off
);

In Parameters

sample: specifies the digital sample that you wish to control.
cut_off: specifies the low-pass filter cutoff frequency. The range is 0.0 to 1.0, given as a fraction of the sample's Nyquist rate.

Discussion

This function allows you to set a low-pass filter on any digital sample (whether uncompressed or compressed). A low-pass filter attenuates frequencies above the cutoff frequency.

The default low-pass cutoff is 1.0 (allowing all frequencies to pass).

The range is 0.0 to 1.0, given as a fraction of the sample's Nyquist rate (which is half the sample rate). For example, if you have a 44100 Hz sample, then the Nyquist rate is 22050 Hz. If you then set a 0.5 cut off, only frequencies under 11025 Hz will be perceived at close to their full amplitude.

In software-mixing contexts, the AIL_set_sample_low_pass_cut_off function is used to implement occlusion, so the two functions cannot be used together on the same HSAMPLE.

There is almost no CPU hit at all with this filter. There is no CPU hit at all on the original Xbox, but the hardware low-pass filter only supports frequencies from 30 to 8000 Hz.

Group: Digital Audio Services
Related Sections: Low-Pass Filter
Related Functions: AIL_sample_low_pass_cut_off, AIL_set_sample_low_pass_cut_off, AIL_set_sample_volume_levels, AIL_set_sample_volume_pan
Related Basic Types: F32, HSAMPLE, void
Related FAQs: How do I apply a low-pass filter?