Files
file	ambe.c
	Osmocom GMR-1 AMBE internal API.

file	frame.c
	Osmocom GMR-1 AMBE speech parameters to/from frame.

file	math.c
	Osmocom GMR-1 AMBE vocoder math functions.

file	private.h
	Osmocom GMR-1 AMBE vocoder private header.

file	synth.c
	Osmocom GMR-1 AMBE vocoder speech synthesis.

file	tables.c
	Osmocom GMR-1 AMBE vocoder tables.

file	tone.c
	Osmocom GMR-1 AMBE vocoder tone frames handling.

Data Structures
struct	ambe_raw_params
	AMBE encoded frame raw parameters. More...

struct	ambe_subframe
	AMBE subframe parameters. More...

struct	ambe_synth
	AMBE synthesizer state. More...

struct	ambe_decoder
	AMBE decoder state. More...

struct	tone_desc
	Structure describing a dual-frequency tone. More...

Macros
#define	AMBE_RATE 8000
	AMBE sample rate (Hz)

#define	M_PIf (3.141592653589793f)
	Value of pi as a float.

Enumerations
enum	ambe_frame_type { AMBE_SPEECH , AMBE_SILENCE , AMBE_TONE }
	AMBE possible frame types. More...

Functions
void	ambe_decode_init (struct ambe_decoder *dec)
	Initializes decoder state. More...

void	ambe_decode_fini (struct ambe_decoder *dec)
	Release all resources associated with a decoder. More...

int	ambe_decode_frame (struct ambe_decoder dec, int16_t audio, int N, const uint8_t *frame, int bad)
	Decodes an AMBE frame to audio. More...

int	ambe_decode_dtx (struct ambe_decoder dec, int16_t audio, int N)
	Generates audio for DTX period. More...

void	ambe_frame_unpack_raw (struct ambe_raw_params rp, const uint8_t frame)
	Unpack a frame into its raw encoded parameters. More...

void	ambe_frame_decode_params (struct ambe_subframe sf, struct ambe_subframe sf_prev, struct ambe_raw_params *rp)
	Decodes the speech parameters for both subframes from raw params. More...

void	ambe_subframe_expand (struct ambe_subframe *sf)
	Expands the decoded subframe params to prepare for synthesis. More...

float	cosf_fast (float angle)
	Fast Cosinus approximation using a simple table. More...

float	sinf_fast (float angle)
	Fast Sinus approximation using a simple table. More...

void	ambe_fdct (float out, float in, int N, int M)
	Forward Discrete Cosine Transform (fDCT) More...

void	ambe_idct (float out, float in, int N, int M)
	Inverse Discrete Cosine Transform (iDCT) More...

void	ambe_fdft_fc (float out_i, float out_q, float *in, int N, int M)
	Forward Discrete Fourrier Transform (float->complex) More...

void	ambe_idft_cf (float out, float in_i, float *in_q, int N, int M)
	Inverse Discret Fourrier Transform (complex->float) More...

void	ambe_synth_init (struct ambe_synth *synth)
	Initialized Synthesizer state. More...

void	ambe_synth_enhance (struct ambe_synth synth, struct ambe_subframe sf)
	Apply the spectral magnitude enhancement on the subframe. More...

void	ambe_synth_audio (struct ambe_synth synth, int16_t audio, struct ambe_subframe sf, struct ambe_subframe sf_prev)
	Generate audio for a given subframe. More...

int	ambe_decode_tone (struct ambe_decoder dec, int16_t audio, int N, const uint8_t *frame)
	Decodes an AMBE tone frame. More...

Variables
const uint8_t	ambe_hpg_tbl [48][4]
	Number of harmonics per group for a given L (starts at L=9)

const float	ambe_gain_tbl [256][2]
	Gain (subframe 0, subframe 1)

const uint16_t	ambe_v_uv_tbl [64]
	V/UV decisions (subframe 0 = low byte. MSBs = low freq)

const float	ambe_prba12_tbl [128][2]
	PRBA[1:2].

const float	ambe_prba34_tbl [64][2]
	PRBA[3:4].

const float	ambe_prba57_tbl [128][3]
	PRBA[5:7].

const float	ambe_hoc0_tbl [128][4]
	HOC for 1st frequency block.

const float	ambe_hoc1_tbl [64][4]
	HOC for 2nd frequency block.

const float	ambe_hoc2_tbl [64][4]
	HOC for 3rd frequency block.

const float	ambe_hoc3_tbl [64][4]
	HOC for last frequency block.

const float	ambe_sf0_interp_tbl [4]
	Interpolation ratios for subframe 0 magnitude prediction.

const float	ambe_sf0_perr14_tbl [64][4]
	Prediction Error [1:4] for subframe 0.

const float	ambe_sf0_perr58_tbl [32][4]
	Prediction Error [5:8] for subframe 0.

const uint8_t	ambe_hpg_tbl [48][4]
	Number of harmonics per group for a given L (starts at L=9)

const float	ambe_gain_tbl [256][2]
	Gain (subframe 0, subframe 1)

const uint16_t	ambe_v_uv_tbl [64]
	V/UV decisions (subframe 0 = low byte. MSBs = low freq) More...

const float	ambe_prba12_tbl [128][2]
	PRBA[1:2].

const float	ambe_prba34_tbl [64][2]
	PRBA[3:4].

const float	ambe_prba57_tbl [128][3]
	PRBA[5:7].

const float	ambe_hoc0_tbl [128][4]
	HOC for 1st frequency block.

const float	ambe_hoc1_tbl [64][4]
	HOC for 2nd frequency block.

const float	ambe_hoc2_tbl [64][4]
	HOC for 3rd frequency block.

const float	ambe_hoc3_tbl [64][4]
	HOC for last frequency block.

const float	ambe_sf0_interp_tbl [4]
	Interpolation ratios for subframe 0 magnitude prediction. More...

const float	ambe_sf0_perr14_tbl [64][4]
	Prediction Error [1:4] for subframe 0.

const float	ambe_sf0_perr58_tbl [32][4]
	Prediction Error [5:8] for subframe 0.

Detailed Description

Enumeration Type Documentation

◆ ambe_frame_type

enum ambe_frame_type

AMBE possible frame types.

Enumerator
AMBE_SPEECH	Speech frame.
AMBE_SILENCE	Silence indication frame.
AMBE_TONE	Tone frame

Function Documentation

◆ ambe_decode_dtx()

int ambe_decode_dtx	(	struct ambe_decoder *	dec,
		int16_t *	audio,
		int	N
	)

Generates audio for DTX period.

Parameters

[in]	dec	Decoder state structure
[out]	audio	Output audio buffer
[in]	N	number of audio samples to produce (152..168)

Referenced by gmr1_codec_decode_dtx().

◆ ambe_decode_fini()

void ambe_decode_fini ( struct ambe_decoder * dec )

Release all resources associated with a decoder.

Parameters

[in] dec Decoder state structure

Referenced by gmr1_codec_release().

◆ ambe_decode_frame()

int ambe_decode_frame	(	struct ambe_decoder *	dec,
		int16_t *	audio,
		int	N,
		const uint8_t *	frame,
		int	bad
	)

Decodes an AMBE frame to audio.

Parameters

[in]	dec	Decoder state structure
[out]	audio	Output audio buffer
[in]	N	number of audio samples to produce (152..168)
[in]	frame	Frame data (10 bytes = 80 bits)
[in]	bad	Bad Frame Indicator. Set to 1 if frame is corrupt

Returns: 0 for success. Negative error code otherwise.

Referenced by gmr1_codec_decode_frame().

◆ ambe_decode_init()

void ambe_decode_init ( struct ambe_decoder * dec )

Initializes decoder state.

Parameters

[in] dec Decoder state structure

References ambe_synth_init(), ambe_subframe::f0, ambe_subframe::L, M_PIf, ambe_decoder::sf_prev, ambe_decoder::synth, and ambe_subframe::w0.

Referenced by gmr1_codec_alloc().

◆ ambe_decode_tone()

int ambe_decode_tone	(	struct ambe_decoder *	dec,
		int16_t *	audio,
		int	N,
		const uint8_t *	frame
	)

Decodes an AMBE tone frame.

Parameters

[in]	dec	AMBE decoder state
[out]	audio	Output audio buffer
[in]	N	number of audio samples to produce (152..168)
[in]	frame	Frame data (10 bytes = 80 bits). Must be tone frame !

Returns: 0 for success. -EINVAL if frame was invalid.

◆ ambe_fdct()

void ambe_fdct	(	float *	out,
		float *	in,
		int	N,
		int	M
	)

Forward Discrete Cosine Transform (fDCT)

Parameters

[out]	out	fDCT result buffer (freq domain, M elements)
[in]	in	fDCT input buffer (time domain, N elements)
[in]	N	Number of points of the DCT
[in]	M	Limit to the number of frequency components (M <= N)

References cosf_fast(), and M_PIf.

◆ ambe_fdft_fc()

void ambe_fdft_fc	(	float *	out_i,
		float *	out_q,
		float *	in,
		int	N,
		int	M
	)

Forward Discrete Fourrier Transform (float->complex)

Parameters

[out]	out_i	Real component result buffer (freq domain, N/2+1 elements)
[out]	out_q	Imag component result buffer (freq domain, N/2+1 elements)
[in]	in	Input buffer (time domain, M elements)
[in]	N	Number of points of the DFT
[in]	M	Limit to to the number of available time domain elements

Since the input is float, the result is symmetric and so only one side is computed. The output index 0 is DC.

References cosf_fast(), M_PIf, and sinf_fast().

◆ ambe_frame_decode_params()

void ambe_frame_decode_params	(	struct ambe_subframe *	sf,
		struct ambe_subframe *	sf_prev,
		struct ambe_raw_params *	rp
	)

Decodes the speech parameters for both subframes from raw params.

Parameters

[out]	sf	Array of 2 subframes data to fill-in
[in]	sf_prev	Previous subframe 1 data
[in]	rp	Encoded frame raw parameters

References ambe_subframe::f0, ambe_subframe::f0log, and ambe_raw_params::pitch.

◆ ambe_frame_unpack_raw()

void ambe_frame_unpack_raw	(	struct ambe_raw_params *	rp,
		const uint8_t *	frame
	)

Unpack a frame into its raw encoded parameters.

Parameters

[out]	rp	Encoded frame raw parameters to unpack into
[in]	frame	Frame data (10 bytes = 80 bits)

References ambe_raw_params::pitch.

◆ ambe_idct()

void ambe_idct	(	float *	out,
		float *	in,
		int	N,
		int	M
	)

Inverse Discrete Cosine Transform (iDCT)

Parameters

[out]	out	iDCT result buffer (time domain, N elements)
[in]	in	iDCT input buffer (freq domain, M elements)
[in]	N	Number of points of the DCT
[in]	M	Limit to the number of frequency components (M <= N)

References cosf_fast(), and M_PIf.

◆ ambe_idft_cf()

void ambe_idft_cf	(	float *	out,
		float *	in_i,
		float *	in_q,
		int	N,
		int	M
	)

Inverse Discret Fourrier Transform (complex->float)

Parameters

[out]	out	Result buffer (time domain, M
[in]	in_i	Real component input buffer (freq domain, N/2+1 elements)
[in]	in_q	Imag component input buffer (freq domain, N/2+1 elements)
[in]	N	Number of points of the DFT
[in]	M	Limit to the number of time domain elements to generate

The input is assumed to be symmetric and so only N/2+1 inputs are needed. DC component must be input index 0.

References cosf_fast(), M_PIf, and sinf_fast().

◆ ambe_subframe_expand()

void ambe_subframe_expand ( struct ambe_subframe * sf )

Expands the decoded subframe params to prepare for synthesis.

Parameters

[in] sf The subframe to expand

References ambe_subframe::f0, ambe_subframe::L, M_PIf, ambe_subframe::Ml, ambe_subframe::Mlog, ambe_subframe::v_uv, ambe_subframe::Vl, and ambe_subframe::w0.

◆ ambe_synth_audio()

void ambe_synth_audio	(	struct ambe_synth *	synth,
		int16_t *	audio,
		struct ambe_subframe *	sf,
		struct ambe_subframe *	sf_prev
	)

Generate audio for a given subframe.

Parameters

[in]	synth	Synthesizer state structure
[out]	audio	Result buffer (80 samples)
[in]	sf	Expanded subframe data for current subframe
[in]	sf_prev	Expanded subframe data for prevous subframe

◆ ambe_synth_enhance()

void ambe_synth_enhance	(	struct ambe_synth *	synth,
		struct ambe_subframe *	sf
	)

Apply the spectral magnitude enhancement on the subframe.

Parameters

[in]	synth	Synthesizer state structure
[in]	sf	Expanded subframe data for subframe to enhance

References cosf_fast(), ambe_subframe::L, M_PIf, ambe_subframe::Ml, ambe_synth::SE, and ambe_subframe::w0.

◆ ambe_synth_init()

void ambe_synth_init ( struct ambe_synth * synth )

Initialized Synthesizer state.

Parameters

[out] synth The structure to reset

References ambe_synth::u_prev.

Referenced by ambe_decode_init().

◆ cosf_fast()

float cosf_fast ( float angle )

Fast Cosinus approximation using a simple table.

Parameters

[in] angle The angle value

Returns: The cosinus of the angle

References M_PIf.

Referenced by ambe_fdct(), ambe_fdft_fc(), ambe_idct(), ambe_idft_cf(), and ambe_synth_enhance().

◆ sinf_fast()

float sinf_fast ( float angle )

Fast Sinus approximation using a simple table.

Parameters

[in] angle The angle value

Returns: The sinus of the angle

References M_PIf.

Referenced by ambe_fdft_fc(), and ambe_idft_cf().

Variable Documentation

◆ ambe_sf0_interp_tbl

const float ambe_sf0_interp_tbl[4]

Initial value:

= {
        0.90f,
        0.70f,
        0.50f,
        0.17f,
}

Interpolation ratios for subframe 0 magnitude prediction.

◆ ambe_v_uv_tbl

const uint16_t ambe_v_uv_tbl[64]

Initial value:

= {
        0x0000, 0xffff, 0xc0c0, 0xe0e0, 0xf0f0, 0x8080, 0xfefe, 0x0080,
        0xfcfc, 0x80c0, 0xf8f8, 0x8000, 0x00c0, 0xfffe, 0xfeff, 0xc000,
        0xf0e0, 0xc0e0, 0xfbfb, 0xfcfe, 0xf8f0, 0xfdfd, 0xfffb, 0xe000,
        0xe0f0, 0xfcff, 0xfdff, 0xe0c0, 0xfffc, 0xf0f8, 0xfefc, 0xfffd,
        0xf8fc, 0xfcf8, 0xfcfd, 0x4000, 0xf0c0, 0xf9f9, 0xfbff, 0xefef,
        0xf3f3, 0xc080, 0xf0e0, 0xfff8, 0xf0fc, 0xf1f1, 0x0040, 0xc0d0,
        0xc0f0, 0xf7f7, 0xfaf8, 0xfafa, 0xfcf0, 0xfef8, 0x00e0, 0x0100,
        0x1000, 0xe0e1, 0xe0f8, 0xf2f0, 0xf8ff, 0xfafe, 0xfff7, 0xdfdf,
}

V/UV decisions (subframe 0 = low byte. MSBs = low freq)

Files

Data Structures

Macros

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ ambe_frame_type

Function Documentation

◆ ambe_decode_dtx()

◆ ambe_decode_fini()

◆ ambe_decode_frame()

◆ ambe_decode_init()

◆ ambe_decode_tone()

◆ ambe_fdct()

◆ ambe_fdft_fc()

◆ ambe_frame_decode_params()

◆ ambe_frame_unpack_raw()

◆ ambe_idct()

◆ ambe_idft_cf()

◆ ambe_subframe_expand()

◆ ambe_synth_audio()

◆ ambe_synth_enhance()

◆ ambe_synth_init()

◆ cosf_fast()

◆ sinf_fast()

Variable Documentation

◆ ambe_sf0_interp_tbl

◆ ambe_v_uv_tbl