echo.h

一个开源的sip源代码

/* $Id: echo.h 974 2007-02-19 01:13:53Z bennylp $ */
/* 
 * Copyright (C) 2003-2007 Benny Prijono <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
 */
#ifndef __PJMEDIA_ECHO_H__
#define __PJMEDIA_ECHO_H__


/**
 * @file echo.h
 * @brief Echo Cancellation  API.
 */
#include <pjmedia/types.h>



/**
 * @defgroup PJMEDIA_Echo_Cancel Accoustic Echo Cancellation API
 * @ingroup PJMEDIA_PORT
 * @brief Echo Cancellation API.
 * @{
 *
 * This section describes API to perform echo cancellation to audio signal.
 * There may be multiple echo canceller implementation in PJMEDIA, ranging
 * from simple echo suppressor to a full Accoustic Echo Canceller/AEC. By 
 * using this API, application should be able to use which EC backend to
 * use base on the requirement and capability of the platform.
 */


PJ_BEGIN_DECL


/**
 * Opaque type for PJMEDIA Echo Canceller state.
 */
typedef struct pjmedia_echo_state pjmedia_echo_state;


/**
 * Echo cancellation options.
 */
typedef enum pjmedia_echo_flag
{
    /**
     * If PJMEDIA_ECHO_SIMPLE flag is specified during echo canceller
     * creation, then a simple echo suppressor will be used instead of
     * an accoustic echo cancellation.
     */
    PJMEDIA_ECHO_SIMPLE	= 1,

    /**
     * If PJMEDIA_ECHO_NO_LOCK flag is specified, no mutex will be created
     * for the echo canceller, but application will guarantee that echo
     * canceller will not be called by different threads at the same time.
     */
    PJMEDIA_ECHO_NO_LOCK = 2

} pjmedia_echo_flag;




/**
 * Create the echo canceller. 
 *
 * @param pool		    Pool to allocate memory.
 * @param clock_rate	    Media clock rate/sampling rate.
 * @param samples_per_frame Number of samples per frame.
 * @param tail_ms	    Tail length, miliseconds.
 * @param latency_ms	    Total lacency introduced by playback and 
 *			    recording device. Set to zero if the latency
 *			    is not known.
 * @param options	    Options. If PJMEDIA_ECHO_SIMPLE is specified,
 *			    then a simple echo suppressor implementation 
 *			    will be used instead of an accoustic echo 
 *			    cancellation.
 *			    See #pjmedia_echo_flag for other options.
 * @param p_echo	    Pointer to receive the Echo Canceller state.
 *
 * @return		    PJ_SUCCESS on success, or the appropriate status.
 */
PJ_DECL(pj_status_t) pjmedia_echo_create(pj_pool_t *pool,
					 unsigned clock_rate,
					 unsigned samples_per_frame,
					 unsigned tail_ms,
					 unsigned latency_ms,
					 unsigned options,
					 pjmedia_echo_state **p_echo );


/**
 * Destroy the Echo Canceller. 
 *
 * @param echo		The Echo Canceller.
 *
 * @return		PJ_SUCCESS on success.
 */
PJ_DECL(pj_status_t) pjmedia_echo_destroy(pjmedia_echo_state *echo );


/**
 * Let the Echo Canceller knows that a frame has been played to the speaker.
 * The Echo Canceller will keep the frame in its internal buffer, to be used
 * when cancelling the echo with #pjmedia_echo_capture().
 *
 * @param echo		The Echo Canceller.
 * @param play_frm	Sample buffer containing frame to be played
 *			(or has been played) to the playback device.
 *			The frame must contain exactly samples_per_frame 
 *			number of samples.
 *
 * @return		PJ_SUCCESS on success.
 */
PJ_DECL(pj_status_t) pjmedia_echo_playback(pjmedia_echo_state *echo,
					   pj_int16_t *play_frm );


/**
 * Let the Echo Canceller knows that a frame has been captured from 
 * the microphone.
 * The Echo Canceller will cancel the echo from the captured signal, 
 * using the internal buffer (supplied by #pjmedia_echo_playback()) 
 * as the FES (Far End Speech) reference.
 *
 * @param echo		The Echo Canceller.
 * @param rec_frm	On input, it contains the input signal (captured 
 *			from microphone) which echo is to be removed.
 *			Upon returning this function, this buffer contain
 *			the processed signal with the echo removed.
 *			The frame must contain exactly samples_per_frame 
 *			number of samples.
 * @param options	Echo cancellation options, reserved for future use.
 *			Put zero for now.
 *
 * @return		PJ_SUCCESS on success.
 */
PJ_DECL(pj_status_t) pjmedia_echo_capture(pjmedia_echo_state *echo,
					  pj_int16_t *rec_frm,
					  unsigned options );


/**
 * Perform echo cancellation.
 *
 * @param echo		The Echo Canceller.
 * @param rec_frm	On input, it contains the input signal (captured 
 *			from microphone) which echo is to be removed.
 *			Upon returning this function, this buffer contain
 *			the processed signal with the echo removed.
 * @param play_frm	Sample buffer containing frame to be played
 *			(or has been played) to the playback device.
 *			The frame must contain exactly samples_per_frame 
 *			number of samples.
 * @param options	Echo cancellation options, reserved for future use.
 *			Put zero for now.
 * @param reserved	Reserved for future use, put NULL for now.
 *
 * @return		PJ_SUCCESS on success.
 */
PJ_DECL(pj_status_t) pjmedia_echo_cancel( pjmedia_echo_state *echo,
					  pj_int16_t *rec_frm,
					  const pj_int16_t *play_frm,
					  unsigned options,
					  void *reserved );


PJ_END_DECL

/**
 * @}
 */


#endif	/* __PJMEDIA_ECHO_H__ */