resampler.h File Reference

Sample-rate conversion for the Bluetooth path (A2DP runs at 44.1 or 48 kHz). More...

#include "audio_player/audio.h"

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Typedefs
typedef struct resampler	resampler_t

Enumerations
enum	resampler_quality_t { RESAMPLER_FAST = 0 , RESAMPLER_GOOD = 1 }

Functions
resampler_t *	resampler_create (uint32_t in_rate, uint32_t out_rate, uint8_t channels, resampler_quality_t q)
	Returns NULL if the conversion is not supported. in_rate == out_rate is allowed (copy).
void	resampler_destroy (resampler_t *r)
void	resampler_reset (resampler_t *r)
uint32_t	resampler_process (resampler_t *r, const int32_t *in, uint32_t in_frames, uint32_t *consumed, int32_t *out, uint32_t out_cap)
	Convert interleaved Q31.
uint32_t	resampler_max_output (const resampler_t *r, uint32_t in_frames)
	Upper bound of output frames for a given input count (for buffer sizing).

Detailed Description

Sample-rate conversion for the Bluetooth path (A2DP runs at 44.1 or 48 kHz).

Integer ratios 2:1 and 4:1 use cascaded half-band decimators (cheap, the common hi-res case). Other ratios (48k -> 44.1k = 147/160) use a polyphase windowed-sinc filter. The wired path never resamples.

Typedef Documentation

resampler_t

typedef struct resampler resampler_t

Enumeration Type Documentation

resampler_quality_t

enum resampler_quality_t

Enumerator
RESAMPLER_FAST	~16 taps/phase, for weak CPUs
RESAMPLER_GOOD	~32 taps/phase, default

Function Documentation

resampler_create()

resampler_t * resampler_create	(	uint32_t	in_rate,
		uint32_t	out_rate,
		uint8_t	channels,
		resampler_quality_t	q
	)

Returns NULL if the conversion is not supported. in_rate == out_rate is allowed (copy).

resampler_destroy()

void resampler_destroy

(

resampler_t *

r

)

resampler_max_output()

uint32_t resampler_max_output	(	const resampler_t *	r,
		uint32_t	in_frames
	)

Upper bound of output frames for a given input count (for buffer sizing).

resampler_process()

uint32_t resampler_process	(	resampler_t *	r,
		const int32_t *	in,
		uint32_t	in_frames,
		uint32_t *	consumed,
		int32_t *	out,
		uint32_t	out_cap
	)

Convert interleaved Q31.

Consumes up to in_frames, writes up to out_cap frames. *consumed receives input frames used. Returns output frames written.

resampler_reset()

void resampler_reset

(

resampler_t *

r

)