src/spandsp/g726.h File Reference

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Classes
struct	g726_state_s
Typedefs
typedef int16_t(*	g726_decoder_func_t )(struct g726_state_s *s, uint8_t code)
typedef uint8_t(*	g726_encoder_func_t )(struct g726_state_s *s, int16_t amp)
typedef struct g726_state_s	g726_state_t
Enumerations
enum	{ G726_ENCODING_LINEAR = 0, G726_ENCODING_ULAW, G726_ENCODING_ALAW }
enum	{ G726_PACKING_NONE = 0, G726_PACKING_LEFT = 1, G726_PACKING_RIGHT = 2 }
Functions
g726_state_t *	g726_init (g726_state_t *s, int bit_rate, int ext_coding, int packing)
int	g726_release (g726_state_t *s)
int	g726_decode (g726_state_t *s, int16_t amp[], const uint8_t g726_data[], int g726_bytes)
int	g726_encode (g726_state_t *s, uint8_t g726_data[], const int16_t amp[], int len)

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Detailed Description

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Typedef Documentation

typedef struct g726_state_s g726_state_t

The following is the definition of the state structure used by the G.726 encoder and decoder to preserve their internal state between successive calls. The meanings of the majority of the state structure fields are explained in detail in the CCITT Recommendation G.721. The field names are essentially indentical to variable names in the bit level description of the coding algorithm included in this Recommendation.

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Function Documentation

int g726_decode	(	g726_state_t *	s,
		int16_t	amp[],
		const uint8_t	g726_data[],
		int	g726_bytes
	)

Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.

Parameters:

	s	The G.726 context.
	amp	The audio sample buffer.
	g726_data
	g726_bytes

Returns:

The number of samples returned.

Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.

Parameters:

	s	The G.726 context.
	amp
	g726_data
	g726_bytes

Returns:

The number of samples returned.

References g726_state_s::bits_per_sample, bitstream_state_t::bitstream, g726_state_s::bs, g726_state_s::dec_func, g726_state_s::ext_coding, g726_state_s::in_bits, g726_state_s::in_buffer, g726_state_s::packing, and bitstream_state_t::residue.

int g726_encode	(	g726_state_t *	s,
		uint8_t	g726_data[],
		const int16_t	amp[],
		int	len
	)

Encode a buffer of linear PCM data to G.726 ADPCM.

Parameters:

	s	The G.726 context.
	g726_data	The G.726 data produced.
	amp	The audio sample buffer.
	len	The number of samples in the buffer.

Returns:

The number of bytes of G.726 data produced.

Encode a buffer of linear PCM data to G.726 ADPCM.

Parameters:

	s	The G.726 context.
	g726_data
	amp
	samples

Returns:

The number of bytes of G.726 data produced.

References g726_state_s::bits_per_sample, bitstream_state_t::bitstream, g726_state_s::bs, g726_state_s::enc_func, g726_state_s::ext_coding, g726_state_s::out_bits, g726_state_s::out_buffer, g726_state_s::packing, and bitstream_state_t::residue.

g726_state_t* g726_init	(	g726_state_t *	s,
		int	bit_rate,
		int	ext_coding,
		int	packing
	)

Initialise a G.726 encode or decode context.

Parameters:

	s	The G.726 context.
	bit_rate	The required bit rate for the ADPCM data. The valid rates are 16000, 24000, 32000 and 40000.
	ext_coding	The coding used outside G.726.
	packing	One of the G.726_PACKING_xxx options.

Returns:

A pointer to the G.726 context, or NULL for error.

References g726_state_s::a, g726_state_s::ap, g726_state_s::b, g726_state_s::bits_per_sample, bitstream_init(), g726_state_s::bs, g726_state_s::dec_func, g726_state_s::dml, g726_state_s::dms, g726_state_s::dq, g726_state_s::enc_func, g726_state_s::ext_coding, g726_state_s::in_bits, g726_state_s::in_buffer, g726_state_s::out_bits, g726_state_s::out_buffer, g726_state_s::packing, g726_state_s::pk, g726_state_s::rate, g726_state_s::sr, g726_state_s::td, g726_state_s::yl, and g726_state_s::yu.

int g726_release

(

g726_state_t *

s

)

Free a G.726 encode or decode context.

Parameters:

s

The G.726 context.

Returns:

0 for OK.