student.cpp

PCM逐次比较法编码译码,CVSD编码译码

//#ifdef __cplusplus
//extern "C" {
//#endif
/*==================================================================================================
Module Name: Student.cpp
General Description: Student write these functions
====================================================================================================
Semit 
(c) Copyright SEMIT 2002, All Rights Reserved
Revision History:
Modification Tracking
------------------------- ------------ ---------- -------------------------------------------
Author         Date       Number      Description of Changes
------------------------- ------------ ----------------------------------------
Semit        08/5/2002    Unknown      A-Law PCM  and CVSD encode and decode functions
====================================================================================================
INCLUDE FILES
==================================================================================================*/
#include <stdafx.h>
#include <math.h>
#include "Student.h"

/*==================================================================================================
LOCAL TYPEDEFS (STRUCTURES, UNIONS, ENUMS)
==================================================================================================*/

/*==================================================================================================
LOCAL VARIABLES
==================================================================================================*/
static STUDENT_CVSD Student_CVSD;
/*==================================================================================================
 *                     GLOBAL FUNCTIONS                                                             
/*==================================================================================================
FUNCTION: PCM_StudentAlawEncode
DESCRIPTION: 
    This function is A-Law PCM encode function
ARGUMENTS PASSED:
    InputValue:  The inputed sample value , the range is -2047 ~ +2047
RETURN VALUE:
    The 8-bits encoded value
PRE-CONDITIONS:
    None
POST-CONDITIONS:
    None
IMPORTANT NOTES:  
==================================================================================================*/
extern unsigned char PCM_StudentAlawEncode(int InputValue) 
{
	unsigned char OutputValue = 0x0;
    /*****************PCM Encode by S.C.H.*********************************************/
	unsigned char s,k,seg,high=0,low=0;
	int sv;
	if(InputValue>0)s=128;
	else s=0;
	InputValue=abs(InputValue);
	if(InputValue>=1024)high=112,sv=1024,k=64;  //判断高三位
	else if(InputValue>=512)high=96,sv=512,k=32;
	     else if(InputValue>=256)high=80,sv=256,k=16;
		      else if(InputValue>=128)high=64,sv=128,k=8;
			       else if(InputValue>=64)high=48,sv=64,k=4;
				        else if(InputValue>=32)high=32,sv=32,k=2;
						     else if(InputValue>=16)high=16,sv=16,k=1;
							      else if(InputValue>=0)high=0,sv=0,k=1;
	if(InputValue>=sv+8*k)low=8;
	else if(InputValue>=sv+4*k)low=4;
	     else if(InputValue>=sv+2*k)low=2;
	          else if(InputValue>=sv+k)low=1;
	seg=low+1;
    switch(low) {                             //判断低四位
    case 8:if(InputValue>=sv+seg*k){low++;seg++;}else break;
		   if(InputValue>=sv+seg*k){low++;seg++;}else break;
		   if(InputValue>=sv+seg*k){low++;seg++;}else break;
		   if(InputValue>=sv+seg*k){low++;seg++;}else break;
    case 4:if(InputValue>=sv+seg*k){low++;seg++;}else break;
		   if(InputValue>=sv+seg*k){low++;seg++;}else break;
	case 2:if(InputValue>=sv+seg*k){low++;}else break;
	case 1:break;
    default:break;
    }
	OutputValue=s+high+low;
    /*****************PCM Encode by S.C.H.*********************************************/
   return OutputValue;
}
/*==================================================================================================
FUNCTION: PCM_StudentAlawDecode
DESCRIPTION: 
    This function is A-Law PCM dencode function
ARGUMENTS PASSED:
    CodeValue:  The 8-bits encoded value 
RETURN VALUE:
    The decoded sample value 
PRE-CONDITIONS:
    None
POST-CONDITIONS:
    None
IMPORTANT NOTES:  
==================================================================================================*/
extern int PCM_StudentAlawDecode(unsigned char CodeValue)
{
	int DecodeValue = 0;

	/*****************PCM Decode by S.C.H.*********************************************/
	char k,s=-1;
	int sv;
	if(CodeValue>=128){s=1;CodeValue-=128;}
	if(CodeValue>=112)sv=1024,k=64;           //确定段起始电平及量化间隔
	else if(CodeValue>=96)sv=512,k=32;
	     else if(CodeValue>=80)sv=256,k=16;
		      else if(CodeValue>=64)sv=128,k=8;
			       else if(CodeValue>=48)sv=64,k=4;
				        else if(CodeValue>=32)sv=32,k=2;
						     else if(CodeValue>=16)sv=16,k=1;
							      else if(CodeValue>=0)sv=0,k=1;
    CodeValue=CodeValue&0x0f;
	DecodeValue=s*(sv+CodeValue*k);
	
    /*****************PCM Decode by S.C.H.*********************************************/

	return DecodeValue;
}
/*==================================================================================================
FUNCTION: CVSD_StudentEncode
DESCRIPTION: 
    This function is CVSD encode function
ARGUMENTS PASSED:
    Amplitude:   The sin wave amplitude , the range is 0 - 32767
	Frequency:   The sin wave frequency , the range is 4*1024 - 16* 1024
	SampleTimes: The times of sample , the range is 10 - 30

The sample value is computed as follows:
    Sample[i]  = Amplitude * sin(2 * PI * Frequency * (double)i /(double)(64*1024));

RETURN VALUE:
    The pointer to struct Student_CVSD, the member 'Encode' of the struct is the cvsd code.
PRE-CONDITIONS:
    None
POST-CONDITIONS:
    None
IMPORTANT NOTES:  
==================================================================================================*/
extern STUDENT_CVSD* CVSD_StudentEncode(int Amplitude, int SampleTimes, int Frequency)
{
    double Sample[30];
	int i;

	for(i = 0; i < SampleTimes; i ++){        /*64khz is the sample frequency*/
        Sample[i]  = Amplitude * sin(2 * PI * Frequency * (double)i /(double)(64*1024));
 	}

 	/*****************CVSD Encode by S.C.H.*********************************************/
	int y[30];
	double old1=0,old2=0,old3=0,dec[30];
	double g[30],k=0.96875,k0=0,dk=10,a=0.9990234375;
    g[0]=0,dec[0]=0;
	for(i=0;i<SampleTimes;i++)
	   {
         if(i)
		{
			
			 if(Sample[i]-g[i]>=0)y[i]=1;
			else y[i]=0;
			if((y[i]==old1) & (y[i]==old2) & (y[i]==old3))
			{
				if(y[i])
				{k0+=dk;}
			}
			else if((a*k0)<=10)k0=10;else k0*=a;
			if(y[i])dec[i]=g[i]+k0;
			else dec[i]=g[i]-k0;
			g[i+1]=dec[i]*k;
			old3=old2;
			old2=old1;
			old1=y[i];			
		}
		else
		{
			if(Sample[i]-g[i]>=0){y[i]=1;dec[i]=g[i]+k0;}else {y[i]=0;dec[i]=g[i]-k0;}
			g[i+1]=dec[i]*k;
		}

		
		Student_CVSD.Encode[i]=y[i];
	   }
    /*****************CVSD Encode by S.C.H.*********************************************/

   return &Student_CVSD;
}
/*==================================================================================================
FUNCTION: CVSD_StudentDecode
DESCRIPTION: 
    This function is CVSD decode function
ARGUMENTS PASSED:
    SampleTimes:  The times of sample
	Use the member 'Encode'of struct Student_CVSD
RETURN VALUE:
    The pointer to struct Student_CVSD, the member 'Decode' of the struct is the decoded value.
PRE-CONDITIONS:
    None
POST-CONDITIONS:
    None
IMPORTANT NOTES:  
==================================================================================================*/
extern STUDENT_CVSD* CVSD_StudentDecode(int SampleTimes)
{
    
	/*****************CVSD Decode by S.C.H.*********************************************/
    int i;
	int old1=0,old2=0,old3=0;
	double g[30],decode[30],k=0.96875,k0=0,dk=10,a=0.9990234375;
	g[0]=0;decode[0]=0;
    for(i=0;i<30;i++)
	{  
		if(i)
		{
			if((Student_CVSD.Encode[i]==old1) & (Student_CVSD.Encode[i]==old2) & (Student_CVSD.Encode[i]==old3))
			{
				if(Student_CVSD.Encode[i])
				{k0+=dk;}
			}
			else  if((a*k0)<=10)k0=10;else k0*=a;
			if(Student_CVSD.Encode[i])g[i]=decode[i]+k0;
			else g[i]=decode[i]-k0;
			old3=old2;
			old2=old1;
			old1=Student_CVSD.Encode[i];
			decode[i+1]=g[i]*k;
		}
		else {if(Student_CVSD.Encode[i])g[i+1]=decode[i]+k0;else g[i+1]=decode[i]-k0;decode[i+1]=g[i]*k;}
		Student_CVSD.Decode[i]=decode[i];
	}
	/*****************CVSD Decode by S.C.H.*********************************************/

    return &Student_CVSD;
}
/*===========================================================================================*/
//#ifdef __cplusplus
//}
//#endif