File syn_audio_mixer.h¶

FileList > audio > syn_audio_mixer.h

Zero-Heap Multi-Channel Q15 Fixed-Point Audio Mixer. More...

#include "../common/syn_defs.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

Classes¶

Type	Name
struct	SYN_Audio_Mixer Audio Mixer Instance State.
struct	SYN_Audio_Mixer_Channel State for a single mixer input channel.

Public Functions¶

Type	Name
SYN_Status	syn_audio_mixer_init (SYN_Audio_Mixer * mixer) Initialize an Audio Mixer instance.
SYN_Status	syn_audio_mixer_play (SYN_Audio_Mixer * mixer, uint8_t channel_idx, const int16_t * pcm_buf, size_t sample_count, uint16_t volume_q15, bool loop) Assign a PCM sample buffer to a mixer channel for playback.
size_t	syn_audio_mixer_render (SYN_Audio_Mixer * mixer, int16_t * out_pcm, size_t sample_count) Render mixed PCM audio into an output sample buffer.
SYN_Status	syn_audio_mixer_set_channel_volume (SYN_Audio_Mixer * mixer, uint8_t channel_idx, uint16_t volume_q15) Adjust gain for a specific channel.
SYN_Status	syn_audio_mixer_set_master_volume (SYN_Audio_Mixer * mixer, uint16_t volume_q15) Adjust master gain across all channels.
SYN_Status	syn_audio_mixer_stop (SYN_Audio_Mixer * mixer, uint8_t channel_idx) Stop channel playback immediately.

Macros¶

Type	Name
define	SYN_AUDIO_GAIN_UNITY `32768U`
define	SYN_AUDIO_MIXER_MAX_CHANNELS `4U`

Detailed Description¶

Provides a zero-malloc multi-channel software PCM audio mixer. Blends multiple active 16-bit PCM audio channels into a single output buffer with per-channel gain, master gain, looping support, and Q15 saturation protection against clipping.

Public Functions Documentation¶

function syn_audio_mixer_init¶

Initialize an Audio Mixer instance.

SYN_Status syn_audio_mixer_init (
    SYN_Audio_Mixer * mixer
)

Parameters:

mixer Pointer to Audio Mixer instance.

Returns:

SYN_OK on success, or SYN_INVALID_PARAM.

function syn_audio_mixer_play¶

Assign a PCM sample buffer to a mixer channel for playback.

SYN_Status syn_audio_mixer_play (
    SYN_Audio_Mixer * mixer,
    uint8_t channel_idx,
    const int16_t * pcm_buf,
    size_t sample_count,
    uint16_t volume_q15,
    bool loop
)

Parameters:

mixer Pointer to Audio Mixer instance.
channel_idx Channel index (0 .. SYN_AUDIO_MIXER_MAX_CHANNELS - 1).
pcm_buf Pointer to 16-bit PCM sample array.
sample_count Sample count in pcm_buf.
volume_q15 Channel gain (Q15, 32768 = 1.0).
loop True to restart automatically upon reaching buffer end.

Returns:

SYN_OK on success, or SYN_INVALID_PARAM.

function syn_audio_mixer_render¶

Render mixed PCM audio into an output sample buffer.

size_t syn_audio_mixer_render (
    SYN_Audio_Mixer * mixer,
    int16_t * out_pcm,
    size_t sample_count
)

Accumulates active channels, applies Q15 scaling, saturates to [-32768, 32767], and writes to out_pcm.

Parameters:

mixer Pointer to Audio Mixer instance.
out_pcm Output 16-bit PCM buffer pointer.
sample_count Output sample count to render.

Returns:

Number of samples actually generated (0 if no active channels or NULL).

function syn_audio_mixer_set_channel_volume¶

Adjust gain for a specific channel.

SYN_Status syn_audio_mixer_set_channel_volume (
    SYN_Audio_Mixer * mixer,
    uint8_t channel_idx,
    uint16_t volume_q15
)

Parameters:

mixer Pointer to Audio Mixer instance.
channel_idx Channel index (0 .. SYN_AUDIO_MIXER_MAX_CHANNELS - 1).
volume_q15 New gain value (Q15).

Returns:

SYN_OK on success, or SYN_INVALID_PARAM / SYN_ERR_OUT_OF_BOUNDS.

function syn_audio_mixer_set_master_volume¶

Adjust master gain across all channels.

SYN_Status syn_audio_mixer_set_master_volume (
    SYN_Audio_Mixer * mixer,
    uint16_t volume_q15
)

Parameters:

mixer Pointer to Audio Mixer instance.
volume_q15 New master gain value (Q15).

Returns:

SYN_OK on success, or SYN_INVALID_PARAM.

function syn_audio_mixer_stop¶

Stop channel playback immediately.

SYN_Status syn_audio_mixer_stop (
    SYN_Audio_Mixer * mixer,
    uint8_t channel_idx
)

Parameters:

mixer Pointer to Audio Mixer instance.
channel_idx Channel index (0 .. SYN_AUDIO_MIXER_MAX_CHANNELS - 1).

Returns:

SYN_OK on success, or SYN_INVALID_PARAM / SYN_ERR_OUT_OF_BOUNDS.

Macro Definition Documentation¶

define SYN_AUDIO_GAIN_UNITY¶

#define SYN_AUDIO_GAIN_UNITY `32768U`

Q15 identity gain (1.0 = 32768)

define SYN_AUDIO_MIXER_MAX_CHANNELS¶

#define SYN_AUDIO_MIXER_MAX_CHANNELS `4U`

Maximum concurrent mixer channels

The documentation for this class was generated from the following file src/syntropic/audio/syn_audio_mixer.h