mixer_t Struct Reference

For ducking, this is the live record that ties threshold_dB, leader_margin_dB, atten_dB, attack_ns together. The owning code creates it, updates it while work is active, and releases its handles and pointed-to storage before freeing the record. More...

#include <include/ascii-chat/audio/mixer.h>

Data Fields
int	num_sources
	Current number of active audio sources.
atomic_t	active_sources
int	max_sources
	Maximum number of sources (allocated array sizes).
int	sample_rate
	Sample rate in Hz (e.g., 44100).
unsigned	channels
struct spectral_processor *	spectral_left [128+1]
struct spectral_processor *	spectral_right [128+1]
audio_ring_buffer_t **	source_buffers
	Array of pointers to client audio ring buffers.
struct mixer_listener_buffer *	listener_buffers [128][128]
const char **	source_ids
	Array of client ID strings (one per source slot).
bool *	source_active
	Array of active flags (true if source is active).
uint64_t	active_sources_mask [((128+63)/64)]
	Bitset of active sources (bit i = source i is active, O(1) iteration).
uint8_t	source_id_to_index [256]
	Hash table mapping client_id → mixer source index (uses hash function for strings).
const char *	source_id_at_hash [256]
	Client ID strings stored at each hash index for collision detection.
rwlock_t	source_lock
	Reader-writer lock protecting source arrays and bitset.
float	crowd_alpha
	Crowd scaling exponent (typically 0.5 for sqrt scaling).
float	base_gain
	Base gain before crowd scaling is applied.
ducking_t	ducking
	Ducking system (active speaker detection and attenuation).
compressor_t	compressor
	Compressor (dynamic range compression).
float *	mix_buffer
	Temporary buffer for mixing operations (pre-allocated).

Detailed Description

For ducking, this is the live record that ties threshold_dB, leader_margin_dB, atten_dB, attack_ns together. The owning code creates it, updates it while work is active, and releases its handles and pointed-to storage before freeing the record.

Main mixer structure for multi-source audio processing

Manages multiple audio sources (clients) and processes them through a professional audio processing pipeline. Supports up to MIXER_MAX_SOURCES simultaneous sources with automatic crowd scaling and active speaker detection.

MIXER ARCHITECTURE:

• Source Management: Array of audio ring buffers, one per client
• Optimized Lookup: Bitset + hash table for O(1) source exclusion
• Thread Safety: Reader-writer locks for concurrent access
• Crowd Scaling: Automatic volume adjustment based on participant count
• Audio Processing: Ducking, compression, noise gate, high-pass filter

PERFORMANCE OPTIMIZATIONS:

• Bitset-based active source tracking (O(1) exclusion)
• Hash table for client ID to mixer index mapping
• Pre-allocated mix buffer (no allocations in hot path)
• Reader-writer locks for concurrent reads

Note

Each source is indexed by position in arrays (0 to max_sources-1). Client IDs are mapped to indices via source_id_to_index hash table.

Active sources are tracked in two ways:

• source_active[] array for per-source status
• active_sources_mask bitset for O(1) iteration exclusion

Warning

Source arrays must be locked (read or write) during iteration to prevent concurrent modifications.

Definition at line 332 of file mixer.h.

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The documentation for this struct was generated from the following file:

• mixer.h