Audio Source (audiosource)

Audio input abstraction supporting multiple input sources.

Structure

struct audio_source_t {
    struct audio_filter_t * filter;
    int (*seek)(struct audio_source_t * s, int offset);
    int (*tell)(struct audio_source_t * s);
    int (*length)(struct audio_source_t * s);
    struct audio_frame_t * (*read)(struct audio_source_t * s);
    int (*ioctl)(struct audio_source_t * s, const char * cmd, void * arg);
    void (*destroy)(struct audio_source_t * s);
    void * priv;
};

Creation Functions

Function	Description
audio_source_alloc()	Allocate an empty Source
audio_source_alloc_from_xfs(ctx, filename)	Read from XFS file (WAV/QOA)
audio_source_alloc_from_capture(name, rate, channel)	Capture from microphone
audio_source_alloc_from_memory(rate, channel, depth, mem, len)	From in-memory PCM data
audio_source_alloc_afsk(mark, space, rate, bit, packet, len)	AFSK modem
audio_source_alloc_tone(type, rate, channel, freq, ms)	Waveform generator
audio_source_alloc_noise(rate, channel)	White noise generator
audio_source_alloc_custom(rate, channel, cb, data)	User-defined callback
audio_source_alloc_from_mixer(mixer)	Wrap a mixer as a Source

Control Functions

Function	Description
audio_source_read(s)	Read an audio frame
audio_source_seek(s, offset)	Seek to a position
audio_source_tell(s)	Get current position
audio_source_length(s)	Get total length
audio_source_get/set_volume(s, vol)	Get/set volume
audio_source_free(s)	Free a Source

Tone Types

audio_source_alloc_tone supports the following waveforms:

Type	Description
"sine"	Sine wave
"square"	Square wave
"triangle"	Triangle wave
"sawtooth"	Sawtooth wave

ioctl Commands

Common ioctl commands (all sources should support):

Command String	shash	arg Type	Description
"audio-source-get-volume"	—	int *	Get volume [0, 1000]
"audio-source-set-volume"	—	int *	Set volume [0, 1000]

audio_source_get_volume() / audio_source_set_volume() are convenience wrappers around these ioctls. Each source can also define its own commands — see each source implementation for details.

Data Flow Convention

audio_source_read(s) internally performs:

return audio_filter_process(s->filter, s->read(s));

That is, the source's built-in filter is automatically applied to the read frame. Use audio_source_filter_apply() to replace or add filters. See Audio Effect and Usage Examples for more.