sems/core/AmMultiPartyMixer.cpp

/*
 * $Id$
 *
 * Copyright (C) 2002-2003 Fhg Fokus
 *
 * This file is part of sems, a free SIP media server.
 *
 * sems 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.
 *
 * For a license to use the sems software under conditions
 * other than those described here, or to purchase support for this
 * software, please contact iptel.org by e-mail at the following addresses:
 *    info@iptel.org
 *
 * sems 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
 */

#include "AmMultiPartyMixer.h"
#include "AmRtpStream.h"
#include "log.h"

#include <assert.h>
#include <math.h>

// PCM16 range: [-32767:32768]
#define MAX_LINEAR_SAMPLE 32737

// the internal delay of the mixer (between put and get)
#define MIXER_DELAY_MS 20
#define MIXER_DELAY    MIXER_DELAY_MS*8  // 8000/1000

AmMultiPartyMixer::AmMultiPartyMixer()
  : channels(),
    cur_channel_id(0),
    scaling_factor(16)
{
}

AmMultiPartyMixer::~AmMultiPartyMixer()
{
}

unsigned int AmMultiPartyMixer::addChannel()
{
  for(;channels.find(cur_channel_id) != channels.end();cur_channel_id++)
    DBG("trying to add channel: #%i\n",cur_channel_id);

  DBG("added channel: #%i\n",cur_channel_id);
  channels.insert(std::make_pair(cur_channel_id,new SampleArrayShort()));

  return cur_channel_id++;
}

void AmMultiPartyMixer::removeChannel(unsigned int channel_id)
{
  delete get_channel(channel_id);
  channels.erase(channel_id);
  DBG("removed channel: #%i\n",channel_id);
}

SampleArrayShort* AmMultiPartyMixer::get_channel(unsigned int channel_id)
{
  ChannelMap::iterator channel_it = channels.find(channel_id);
  if(channel_it == channels.end()){
    ERROR("channel #%i does not exist\n",channel_id);
    return NULL;
  }
    
  return channel_it->second;
}

void AmMultiPartyMixer::PutChannelPacket(unsigned int   channel_id,
					 unsigned int   ts, 
					 unsigned char* buffer, 
					 unsigned int   size)
{
  if(!size) return;
  assert(size <= AUDIO_BUFFER_SIZE);
    
  SampleArrayShort* channel = 0;
  if((channel = get_channel(channel_id)) != 0){

    unsigned samples = PCM16_B2S(size);
    unsigned int put_ts = ts + MIXER_DELAY;

    channel->put(put_ts,(short*)buffer,samples);
    mixed_channel.get(put_ts,tmp_buffer,samples);
	
    mix_add(tmp_buffer,tmp_buffer,(short*)buffer,samples);
    mixed_channel.put(put_ts,tmp_buffer,samples);
  }
  else {
    ERROR("MultiPartyMixer::PutChannelPacket: "
	  "channel #%i doesn't exist\n",channel_id);
  }

}

void AmMultiPartyMixer::GetChannelPacket(unsigned int   channel_id,
					 unsigned int   ts, 
					 unsigned char* buffer, 
					 unsigned int   size)
{
  if(!size) return;
  assert(size <= AUDIO_BUFFER_SIZE);

  SampleArrayShort* channel = 0;
  if((channel = get_channel(channel_id)) != 0){

    unsigned int samples = PCM16_B2S(size);

    mixed_channel.get(ts,tmp_buffer,samples);
    channel->get(ts,(short*)buffer,samples);

    mix_sub(tmp_buffer,tmp_buffer,(short*)buffer,samples);
    scale((short*)buffer,tmp_buffer,samples);
  }
  else {
    ERROR("MultiPartyMixer::GetChannelPacket: "
	  "channel #%i doesn't exist\n",channel_id);
  }
}

// int   dest[size/2]
// int   src1[size/2]
// short src2[size/2]
//
void AmMultiPartyMixer::mix_add(int* dest,int* src1,short* src2,unsigned int size)
{
  int* end_dest = dest + size;

  while(dest != end_dest)
    *(dest++) = *(src1++) + int(*(src2++));
}

void AmMultiPartyMixer::mix_sub(int* dest,int* src1,short* src2,unsigned int size)
{
  int* end_dest = dest + size;

  while(dest != end_dest)
    *(dest++) = *(src1++) - int(*(src2++));
}

void AmMultiPartyMixer::scale(short* buffer,int* tmp_buf,unsigned int size)
{
  short* end_dest = buffer + size;
    
  if(scaling_factor<64)
    scaling_factor++;
    
  while(buffer != end_dest){
	
    int s = (*tmp_buf * scaling_factor) >> 6;
    if(abs(s) > MAX_LINEAR_SAMPLE){
      scaling_factor = abs( (MAX_LINEAR_SAMPLE<<6) / (*tmp_buf) );
      if(s < 0)
	s = -MAX_LINEAR_SAMPLE;
      else
	s = MAX_LINEAR_SAMPLE;
    }
    *(buffer++) = short(s);
    tmp_buf++;
  }
}