read_sound_input (3) - Linux Man Pages
read_sound_input: Retrieves the last recorded audio buffer. Allegro game programming library.
NAMEread_sound_input - Retrieves the last recorded audio buffer. Allegro game programming library.
DESCRIPTIONRetrieves the most recently recorded audio buffer into the specified location. The buffer size can be obtained by checking the return value from start_sound_input(). You must be sure to call this function at regular intervals during the recording (typically around 100 times a second), or some data will be lost. If you are unable to do this often enough from the mainline code, use the digi_recorder() callback to store the waveform into a larger buffer of your own.
Note: many cards produce a click or popping sound when switching between record and playback modes, so it is often a good idea to discard the first buffer after you start a recording. The waveform is always stored in unsigned format, with stereo data consisting of alternate left/right samples.
RETURN VALUEThe function will return non-zero if a buffer has been copied or zero if no new data is yet available (you were too fast checking the input).