drivers/staging/echo/oslec.h

   1 /*
   2  *  OSLEC - A line echo canceller.  This code is being developed
   3  *          against and partially complies with G168. Using code from SpanDSP
   4  *
   5  * Written by Steve Underwood <steveu@coppice.org>
   6  *         and David Rowe <david_at_rowetel_dot_com>
   7  *
   8  * Copyright (C) 2001 Steve Underwood and 2007-2008 David Rowe
   9  *
  10  * All rights reserved.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License version 2, as
  14  * published by the Free Software Foundation.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  24  *
  25  */
  26
  27 #ifndef __OSLEC_H
  28 #define __OSLEC_H
  29
  30 /* TODO: document interface */
  31
  32 /* Mask bits for the adaption mode */
  33 #define ECHO_CAN_USE_ADAPTION   0x01
  34 #define ECHO_CAN_USE_NLP        0x02
  35 #define ECHO_CAN_USE_CNG        0x04
  36 #define ECHO_CAN_USE_CLIP       0x08
  37 #define ECHO_CAN_USE_TX_HPF     0x10
  38 #define ECHO_CAN_USE_RX_HPF     0x20
  39 #define ECHO_CAN_DISABLE        0x40
  40
  41 /*!
  42     G.168 echo canceller descriptor. This defines the working state for a line
  43     echo canceller.
  44 */
  45 struct oslec_state;
  46
  47 /*! Create a voice echo canceller context.
  48     \param len The length of the canceller, in samples.
  49     \return The new canceller context, or NULL if the canceller could not be created.
  50 */
  51 struct oslec_state *oslec_create(int len, int adaption_mode);
  52
  53 /*! Free a voice echo canceller context.
  54     \param ec The echo canceller context.
  55 */
  56 void oslec_free(struct oslec_state *ec);
  57
  58 /*! Flush (reinitialise) a voice echo canceller context.
  59     \param ec The echo canceller context.
  60 */
  61 void oslec_flush(struct oslec_state *ec);
  62
  63 /*! Set the adaption mode of a voice echo canceller context.
  64     \param ec The echo canceller context.
  65     \param adapt The mode.
  66 */
  67 void oslec_adaption_mode(struct oslec_state *ec, int adaption_mode);
  68
  69 void oslec_snapshot(struct oslec_state *ec);
  70
  71 /*! Process a sample through a voice echo canceller.
  72     \param ec The echo canceller context.
  73     \param tx The transmitted audio sample.
  74     \param rx The received audio sample.
  75     \return The clean (echo cancelled) received sample.
  76 */
  77 int16_t oslec_update(struct oslec_state *ec, int16_t tx, int16_t rx);
  78
  79 /*! Process to high pass filter the tx signal.
  80     \param ec The echo canceller context.
  81     \param tx The transmitted auio sample.
  82     \return The HP filtered transmit sample, send this to your D/A.
  83 */
  84 int16_t oslec_hpf_tx(struct oslec_state *ec, int16_t tx);
  85
  86 #endif /* __OSLEC_H */