SpeexEchoState: Acoustic echo canceller

Classes
class	SpeexEchoState

Macros
#define	SPEEX_ECHO_GET_FRAME_SIZE   3
#define	SPEEX_ECHO_SET_SAMPLING_RATE   24
#define	SPEEX_ECHO_GET_SAMPLING_RATE   25
#define	SPEEX_ECHO_GET_IMPULSE_RESPONSE_SIZE   27
#define	SPEEX_ECHO_GET_IMPULSE_RESPONSE   29

Typedefs
typedef struct SpeexEchoState_	SpeexEchoState
typedef struct SpeexDecorrState_	SpeexDecorrState

Functions
SpeexEchoState *	speex_echo_state_init (int frame_size, int filter_length)
SpeexEchoState *	speex_echo_state_init_mc (int frame_size, int filter_length, int nb_mic, int nb_speakers)
void	speex_echo_state_destroy (SpeexEchoState *st)
void	speex_echo_cancellation (SpeexEchoState *st, const spx_int16_t *rec, const spx_int16_t *play, spx_int16_t *out)
void	speex_echo_cancel (SpeexEchoState *st, const spx_int16_t *rec, const spx_int16_t *play, spx_int16_t *out, spx_int32_t *Yout)
void	speex_echo_capture (SpeexEchoState *st, const spx_int16_t *rec, spx_int16_t *out)
void	speex_echo_playback (SpeexEchoState *st, const spx_int16_t *play)
void	speex_echo_state_reset (SpeexEchoState *st)
int	speex_echo_ctl (SpeexEchoState *st, int request, void *ptr)
SpeexDecorrState *	speex_decorrelate_new (int rate, int channels, int frame_size)
void	speex_decorrelate (SpeexDecorrState *st, const spx_int16_t *in, spx_int16_t *out, int strength)
void	speex_decorrelate_destroy (SpeexDecorrState *st)

Detailed Description

This is the acoustic echo canceller module.

Macro Definition Documentation

#define SPEEX_ECHO_GET_FRAME_SIZE   3

Obtain frame size used by the AEC

#define SPEEX_ECHO_GET_IMPULSE_RESPONSE   29

Get impulse response (int32[])

#define SPEEX_ECHO_GET_IMPULSE_RESPONSE_SIZE   27

Get size of impulse response (int32)

#define SPEEX_ECHO_GET_SAMPLING_RATE   25

Get sampling rate

#define SPEEX_ECHO_SET_SAMPLING_RATE   24

Set sampling rate

Typedef Documentation

typedef struct SpeexEchoState_ SpeexEchoState

Internal echo canceller state. Should never be accessed directly.

Function Documentation

void speex_decorrelate	(	SpeexDecorrState *	st,
		const spx_int16_t *	in,
		spx_int16_t *	out,
		int	strength
	)

Remove correlation between the channels by modifying the phase and possibly adding noise in a way that is not (or little) perceptible.

Parameters

st	Decorrelator state
in	Input audio in interleaved format
out	Result of the decorrelation (out may alias in)
strength	How much alteration of the audio to apply from 0 to 100.

void speex_decorrelate_destroy

(

SpeexDecorrState *

st)

Destroy a Decorrelation state

Parameters

st	State to destroy

SpeexDecorrState* speex_decorrelate_new	(	int	rate,
		int	channels,
		int	frame_size
	)

Create a state for the channel decorrelation algorithm This is useful for multi-channel echo cancellation only

Parameters

rate	Sampling rate
channels	Number of channels (it's a bit pointless if you don't have at least 2)
frame_size	Size of the frame to process at ones (counting samples per channel)

void speex_echo_cancel	(	SpeexEchoState *	st,
		const spx_int16_t *	rec,
		const spx_int16_t *	play,
		spx_int16_t *	out,
		spx_int32_t *	Yout
	)

Performs echo cancellation a frame (deprecated)

void speex_echo_cancellation	(	SpeexEchoState *	st,
		const spx_int16_t *	rec,
		const spx_int16_t *	play,
		spx_int16_t *	out
	)

Performs echo cancellation a frame, based on the audio sent to the speaker (no delay is added to playback in this form)

Parameters

st	Echo canceller state
rec	Signal from the microphone (near end + far end echo)
play	Signal played to the speaker (received from far end)
out	Returns near-end signal with echo removed

void speex_echo_capture	(	SpeexEchoState *	st,
		const spx_int16_t *	rec,
		spx_int16_t *	out
	)

Perform echo cancellation using internal playback buffer, which is delayed by two frames to account for the delay introduced by most soundcards (but it could be off!)

Parameters

st	Echo canceller state
rec	Signal from the microphone (near end + far end echo)
out	Returns near-end signal with echo removed

int speex_echo_ctl	(	SpeexEchoState *	st,
		int	request,
		void *	ptr
	)

Used like the ioctl function to control the echo canceller parameters

Parameters

st	Echo canceller state
request	ioctl-type request (one of the SPEEX_ECHO_* macros)
ptr	Data exchanged to-from function

Returns

0 if no error, -1 if request in unknown

void speex_echo_playback	(	SpeexEchoState *	st,
		const spx_int16_t *	play
	)

Let the echo canceller know that a frame was just queued to the soundcard

Parameters

st	Echo canceller state
play	Signal played to the speaker (received from far end)

void speex_echo_state_destroy

(

SpeexEchoState *

st)

Destroys an echo canceller state

Parameters

st	Echo canceller state

SpeexEchoState* speex_echo_state_init	(	int	frame_size,
		int	filter_length
	)

Creates a new echo canceller state

Parameters

frame_size	Number of samples to process at one time (should correspond to 10-20 ms)
filter_length	Number of samples of echo to cancel (should generally correspond to 100-500 ms)

Returns

Newly-created echo canceller state

SpeexEchoState* speex_echo_state_init_mc	(	int	frame_size,
		int	filter_length,
		int	nb_mic,
		int	nb_speakers
	)

Creates a new multi-channel echo canceller state

Parameters

frame_size	Number of samples to process at one time (should correspond to 10-20 ms)
filter_length	Number of samples of echo to cancel (should generally correspond to 100-500 ms)
nb_mic	Number of microphone channels
nb_speakers	Number of speaker channels

Returns

Newly-created echo canceller state

void speex_echo_state_reset

(

SpeexEchoState *

st)

Reset the echo canceller to its original state

Parameters

st	Echo canceller state