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rx.c
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rx.c
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///////////////////////////////////////////////
//
// **************************
//
// Project/Software name: X-Phone
// Author: "Van Gegel" <[email protected]>
//
// THIS IS A FREE SOFTWARE AND FOR TEST ONLY!!!
// Please do not use it in the case of life and death
// This software is released under GNU LGPL:
//
// * LGPL 3.0 <http://www.gnu.org/licenses/lgpl.html>
//
// You’re free to copy, distribute and make commercial use
// of this software under the following conditions:
//
// * You have to cite the author (and copyright owner): Van Gegel
// * You have to provide a link to the author’s Homepage: <http://torfone.org>
//
///////////////////////////////////////////////
//This file contains receiving procedures for PairPhone:
//We records some 48KHz audio samples from Line, collects in the input buffer,
//synchronously demodulates while receives full 81 bits block,
//check for data type is voice or control, decrypt/decode or put silence,
//resampled depends actual buffer state and play 8KHz audio over Speaker.
//Estimated overall voice latency
//On the transmission side:
//delay of recording Mike buffer is 22.5mS
//delay of MELPE coder frame is 67.5 mS
//delay of Line playing buffer is 45 mS
//On the transport: channel latency of GSM depends external conditions
//On the receiving side:
//delay of Line receiving buffer is 22.5 mS
//delay of MELPE decoder frame is 67.5 mS
//delay of Speaker playing buffer is 45 mS
//Total latency average 270 mS + GSM latency (typically 180 mS)
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef _WIN32
#include <stddef.h>
#include <stdlib.h>
#include <basetsd.h>
#include <stdint.h>
#include <windows.h>
#include <time.h>
#else
#include <time.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#endif
#include "audio/audio.h" //low-level audio input/output
#include "modem/modem.h" //modem
#include "melpe/melpe.h" //audio codec
#include "crp.h" //data processing
#include "rx.h" //this
//Global variables
//baseband processing
static short speech[360*6]; //PCM 48KHz input buffer for samples received from the line
static short *samples=speech; //pointer to samples ready for processing
static int cnt=0; //the number of unprocessed samples
static unsigned char buf[12]; //demodulators data output
short sp[544]; //ouputted speech frame
//resampling
float qff=1.0; //resampling ratio
static float up_pos=1.0; //resampler fractional position
static short left_sample=0; //base sample
//playing
static short jit_buf[800]; //PCM 8KHz buffer for samples ready for playing over Speaker
//static short* p_jit_buf=jit_buf; //pointer to unplayed samples in the buffer
static short l_jit_buf=0; //number of unplayed samples in the buffer
static int q_jit_buf=0; //pointer to unplayed samples in the buffer
static float fdelay=7200; //averages playing delay
//accumulators
static float fber=0; //Average bit error rate
static float fau=0; //Average authentication level
//internal procedures
static int resample(short* src, short* dest, float fstep); //resumpling before playing
static int playjit(void); //playing buffered samples
////////////////////////////////////////////////////////////////////////////
//for TEST
//**********************************************************
int rxbit=0;
int rxerr=0;
static float verrs=0;
//bits set lookup table
static const unsigned char BitsSetTable256[256] =
{
# define B2(n) n, n+1, n+1, n+2
# define B4(n) B2(n), B2(n+1), B2(n+1), B2(n+2)
# define B6(n) B4(n), B4(n+1), B4(n+1), B4(n+2)
B6(0), B6(1), B6(1), B6(2)
};
//emulation of encoder for test
void melpe_s_emu( short* ssp, unsigned char* sbuf)
{
int i=0;
int j=0;
float fi;
for(i=0;i<10;i++) j+=BitsSetTable256[sbuf[i]];
verrs*=0.9;
verrs+=j;
rxbit+=80;
rxerr+=j;
for(i=0;i<540;i++)
{
fi=i;
fi=sin(2*M_PI*fi/9);
ssp[i]=(short)(4000*fi);
}
}
//Change samples rate (from PGPFone)
int RateChange(short *src, short *dest, int srcLen, int srcRate, int destRate)
{
//int srcRate = 8000;
short *sourceShortPtr;
short *destShortPtr;
float nSrcRate, nDestRate;
nSrcRate = srcRate;
nDestRate = destRate;
// All samples are 16 bit signed values. Pass in the number of source samples,
// the sample rate of the source data, and the required destination sample
// rate.
if(!srcLen)
return 0;
// If the sample rates are identical, just copy the data over
if(srcRate == destRate)
{
memcpy((char*)dest, (char*)src, srcLen*2);
return srcLen;
}
sourceShortPtr = src;
destShortPtr = dest;
// Downsample
if(srcRate > destRate)
{
float destStep = nDestRate / nSrcRate;
float position = 0;
while(srcLen)
{
int destSample = 0;
int count = 0;
// Accumulate source samples, until the fractional destination position
// crosses a boundary (or we run out of source data)
while(srcLen && (position < 1.0))
{
destSample += *sourceShortPtr++;
srcLen--;
position += destStep;
count++;
}
position = position - 1.0;
*destShortPtr++ = (destSample/count);
}
}
else // Upsample
{
float sourceStep = nSrcRate / nDestRate;
float position = 0;
while(--srcLen)
{
int leftSample = *sourceShortPtr++;
int sampleDifference = *sourceShortPtr-leftSample;
while(position < 1.0)
{
*destShortPtr++ = leftSample + ((float)sampleDifference * position);
position += sourceStep;
}
position = position - 1.0;
}
}
// Return the number of samples written
// Note that this code will sometimes (often?) write one sample too many, so make
// sure your destination buffer is oversized by one.
return destShortPtr - dest;
}
//End of test area
////////////////////////////////////////////////////////////////////////////
//*****************************************************************************
//----------------Streaming resampler--------------------------------------------
static int resample(short* src, short* dest, float fstep)
{
//resampled MELPE frame (540 short 8KHz samples) to specified rate
//input: pointer to source and resulting short samples, resulting ratio
//output: samples in dest resumpled from 8KHz to specified sample rate
//returns: resulting length in samples
int i, diff=0;
short* sptr=src; //source
short* dptr=dest; //destination
//process 540 samples
for(i=0;i<540;i++) //process MELPE frame
{
diff = *sptr-left_sample; //computes difference between current and basic samples
while(up_pos <= 1.0) //while position not crosses a boundary
{
*dptr++ = left_sample + ((float)diff * up_pos); //set destination by basic, difference and position
up_pos += fstep; //move position forward to fractional step
}
left_sample = *sptr++; //set current sample as a basic
up_pos = up_pos - 1.0; //move position back to one outputted sample
}
return dptr-dest; //number of outputted samples
}
//*****************************************************************************
//*****************************************************************************
//--Playing over Speaker----------------------------------
static int playjit(void)
{
//play 8KHz samples in buffer over Speaker
int i=0;
int job=0;
if(l_jit_buf>0) //we have unplayed samples, try to play
{
i=soundplay(l_jit_buf, (unsigned char*)(jit_buf+q_jit_buf)); //play, returns number of played samples
if(i) job+=2; //set job
if((i<0)||(i>l_jit_buf)) i=0; //must play again if underrun (PTT mode etc.)
l_jit_buf-=i; //decrease number of unplayed samples
if(l_jit_buf<0) l_jit_buf=0;
q_jit_buf+=i; //move pointer to unplayed samples
if((l_jit_buf<180)&&(q_jit_buf>0)) //all samples played
{
//memcpy((char*)jit_buf, (char*)(jit_buf+q_jit_buf), 2*l_jit_buf);
for(i=0;i<l_jit_buf;i++) jit_buf[i]=jit_buf[i+q_jit_buf]; //move tail
q_jit_buf=0; //move pointer to the start of empty buffer
}
}
return job; //job flag
}
//*****************************************************************************
//receiving loop: grab 48KHz baseband samples from Line,
//demodulate, decrypt, decode, play 8KHz voice over Speaker
int rx(int typing)
{
//input: -1 for no typing chars, 1 - exist some chars in input buffer
//output: 0 - no any jobs doing, 1 - some jobs were doing
int i;
float f;
int job=0; //flag of any job were doing
char lag_flag=0; //block lag is locked (modems synchronization complete)
//char lock_flag=0; //phase of carrier (1333Hz, 6 samples per period) is locked
//char sync_flag=0; //the difference of frequency transmitter-to-receiver sampling rate is locked
//char current_lag=0; //block lag (0-90, aligned to last bit position, the 6 samples for bit)
char info[8]={0}; //call info
//regularly play Speaker's buffer
job=playjit(); //the first try to play a tail of samples in buffer
//check for we have enough samples for demodulation
if(cnt<180*6) //check we haven't enough of unprocessed samples
{
//move tail to start of receiving buffer
if(samples>speech) //check for tail
{
for(i=0; i<cnt; i++) speech[i]=samples[i]; //move tail to start of buffer
samples=speech; //set pointer to start of buffer
}
//record
i=_soundgrab((char*)(samples+cnt), 180*6); //try to grab new 48KHZ samples from Line
if((i>0)&&(i<=(180*6))) //some samples grabbed
{
cnt+=i; //add grabbed samples to account
job+=4; //set job
}
}
else //we have enough samples for processing
{
i=Demodulate(samples, buf); //process samples: 36*6 (35-37)*6 samples
samples+=i; //move pointer to next samples (with frequency adjusting)
cnt-=i; //decrease the number of unprocessed samples
if(0x80&buf[11]) //checks flag for output data block is ready
{
//check for synck and averages BER
lag_flag=!(!(buf[11]&0x40)); //block lag is locked (synchronization compleet)
//lock_flag=!(!(buf[11]&0x20)); //phaze of carrier (1333Hz, 6 samples per period) is locked
//sync_flag=!(!(buf[11]&0x10)); //the differency of frequency transmitter-to-receiver sampling rate is locked
//current_lag=buf[10]>>1; //block lag (0-90, aligned to last bit position, the 6 samples for bit)
if(lag_flag) //check modem sync
{
//averages BER
i=(0x0F&buf[11]); //count symbols errors (only 1 error per 9-bit symbol can be detected)
fber*=0.99; //fber in range 0-900
fber+=i; //in range 0-9 errored bits per 90 bits treceived
}
//output statistics
if(typing<0) //output call's info if no characters were typed by user
{
f=Mute(0); //get packets counter value
i=State(0); //get current connection step * vad flag
//notification of state and voice output
if(!i) strcpy(info, (char*)"IDLE");
else if(abs(i)<8) strcpy(info, (char*)"CALL");
else if(f<=0) strcpy(info, (char*)"MUTE");
else if(i<0) strcpy(info, (char*)"PAUS");
else strcpy(info, (char*)"TALK");
if(f<0) f=-f; //absolute value
i=f*0.0675; //computes total time of the call in sec: each packet 67,5 ms
f=fau/4-100; //computes authentification level in %
if(f<0) f=0; //only positive results have reason
//current state notification
if(lag_flag) printf("%s %dmin %dsec BER:%0.02f AU:%d%%\r", info, i/60, i%60, fber/90, (int)f);
else printf("%s %dmin %dsec BER:---- AU:%d%%\r", info, i/60, i%60, (int)f); //lost of sync in modem
}
//process received packet detects voice/silence type
buf[11]=0xFE; //set flag default as for silence descriptor
if(lag_flag) //check modem sync
{
i=ProcessPkt(buf); //decode received packet
if(i>=0) //received packet is a control type
{
fau*=0.99; //fau in range 0-800 (400 for random data)
fau+=i; //averages authentication level
}
else if(i==-3)
{
buf[11]=0xFF; //set flag for voice data received
}
} //end of sync ok, packets processing
} //end of data block received
} //end of a portion of sampless processing
//check we have received data and output buffer is empty for decoding
if((0x0E&buf[11])&&(l_jit_buf<=180))
{
//decode voice data or set silency
job+=16; //set job
if(1&buf[11]) //this is a voice frame, decode it
{
melpe_s(sp, buf); //decode 81 bits in 11 bytes to 540 8KHz samples
}
else memset(sp, 0, 1080); //or output 67.5 mS of silence
buf[11]=0; //clears flag: data buffer is processed
//computes average playing delay
i=getdelay()+l_jit_buf; //total number of unplayed samples in buffers
fdelay*=0.9; //averages
fdelay+=i;
//computes optimal resapling ratio for the optimum delay
f=fabs(fdelay/10-720)/10000000; //correction rate due inconsistency
if(i<360) qff-=f; //adjust current ratio
else if(i>1080) qff+=f;
if(qff<0.888) qff=0.888; //restrictions
else if(qff>1.142) qff=1.142;
//resample and play to Headset
if(l_jit_buf>180) l_jit_buf=0; //prevent overflow
l_jit_buf+=resample(sp, jit_buf+l_jit_buf, qff); //resample buffer for playing
playjit(); //immediately try to play buffer
}
return job;
}
//----------------------Setup----------------------------------
//*****************************************************************************
//initialize audio devices
int audio_init(void)
{
if(!_soundinit()) //init audio8 play/rec Headset and audio48 play/rec Line
{
printf("Error of 'Line' audio device initialization, application terminated\r\n");
return 1; //init Headset side 8KHz audio device
}
if(!soundinit())
{
return 2; //init Line side 48KHz audio device
printf("Error of 'Headset' audio device initialization, application terminated\r\n");
}
printf("\r\n");
_soundrec(1); //start records from Line
soundrec(1); //start recrds from Mike
melpe_i(); //init MELPE1200 codec engine
return 0; //success
}
//*****************************************************************************
//finalize audio devices
void audio_fin(void)
{
_soundterm();
soundterm();
}