?? viterbi216.cpp
字號:
#include "viterbi216.h"
//-----以下為函數部分-----
//---------------------------------------------------------------------------
CViterbi_216::CViterbi_216()
{
Decode_States = 64; //狀態數 2^m*k0
Branch_Num = 2; //從一個狀態延伸的分支數 n0
Path_Length = 64; //路徑保留長度 5*m < L < 10*m
Path_Num = 32; //保存幸存路徑個數
First_Use = 1;
Initial();
}
//---------------------------------------------------------------------------
CViterbi_216::~CViterbi_216()
{
;
}
//---------------------------------------------------------------------------
void CViterbi_216::Initial()
{
unsigned char NowStates;
int OneNum;
int i, j;
//狀態發生器：產生2^k0*m_個狀態和分支值
for(i=0; i<Decode_States; i++){
for(j=0; j<Branch_Num; j++){
NowStates = (i<<1) | j;
OneNum = WeightInt(NowStates & G1);
Branch_Tab[i][j] = OneNum % 2;
OneNum = WeightInt(NowStates & G2);
Branch_Tab[i][j] = (Branch_Tab[i][j] << 1) | (OneNum % 2);
}
}
Init_Num = 0;//幸存路徑預裝載個數，Init_Num 的計算方法如下 2^Init_Num = Path_Num
i = Path_Num;
while(i > 1){
Init_Num++;
i = i / 2;
}
}
//---------------------------------------------------------------------------
int CViterbi_216::Viterbi216(unsigned char *InBuf, int InLength, unsigned char *OutBuf, int Star_Mode)
{
int i, j, p;
int ReadBit = 0;
int WriteByte = 0;
int OutBit = 0;
int Now_States = 0;
int Temp_d, Temp_Hm, Temp_Lm;
unsigned char NowCod;
//表示處理非連續卷積碼編碼數據或者連續卷積碼編碼數據的第一個緩存
if((Star_Mode == 0) | (First_Use == 1)){
//初始化幸存路徑結構
for(i=0; i<Path_Num; i++){
Survivor_Save[i].Sum_d = 0;
Survivor_Save[i].H_m32 = 0;
Survivor_Save[i].L_m32 = 0;
}
//首先：將幸存路徑存儲緩存裝載滿
for(i=0,j=1; i<Init_Num; i++){
//每個時刻輸出2比特，和接收序列對應時刻的碼組比較漢明距離
NowCod = InBuf[ReadBit/8] >> (6-ReadBit%8);//從接收序列中取出一個碼組
NowCod = NowCod & 0x03;
ReadBit += 2;
//累加器：進行距離累加
for(p=0; p<j; p++){
Survivor_Save[p].Sum_d = Survivor_Temp[p].Sum_d;
Survivor_Save[p].H_m32 = Survivor_Temp[p].H_m32;
Survivor_Save[p].L_m32 = Survivor_Temp[p].L_m32;
Now_States = char(Survivor_Save[p].L_m32 & 0x3f);
Survivor_Temp[p].Sum_d = Survivor_Save[p].Sum_d +
WeightInt(NowCod ^ Branch_Tab[Now_States][0]);
Survivor_Temp[p].L_m32 = (Survivor_Save[p].L_m32<<1) | 0;
Survivor_Temp[p+j].Sum_d = Survivor_Save[p].Sum_d +
WeightInt(NowCod ^ Branch_Tab[Now_States][1]);
Survivor_Temp[p+j].L_m32 = (Survivor_Save[p].L_m32<<1) | 1;
}
j = 2 * j;
for(p=0; p<j; p++){
Survivor_Save[p].Sum_d = Survivor_Temp[p].Sum_d;
Survivor_Save[p].H_m32 = Survivor_Temp[p].H_m32;
Survivor_Save[p].L_m32 = Survivor_Temp[p].L_m32;
}
}
//用選擇法對Survivor_Save[].Sum_d按由小到大排序
//在此可以不排序，但是排序后效果更好，可以減少Path_Num的個數
/*for(i=0; i<Path_Num-1; i++){
for(j=i+1; j<Path_Num; j++){
if(Survivor_Save[j].Sum_d < Survivor_Save[i].Sum_d){
Temp_d = Survivor_Save[i].Sum_d;
Temp_Hm = Survivor_Save[i].H_m32;
Temp_Lm = Survivor_Save[i].L_m32;
Survivor_Save[i].Sum_d = Survivor_Save[j].Sum_d;
Survivor_Save[i].H_m32 = Survivor_Save[j].H_m32;
Survivor_Save[i].L_m32 = Survivor_Save[j].L_m32;
Survivor_Save[j].Sum_d = Temp_d;
Survivor_Save[j].H_m32 = Temp_Hm;
Survivor_Save[j].L_m32 = Temp_Lm;
}
}
}//*/
OutBit = Init_Num;
First_Use = 0;
}
//第二步：對數據進行糾錯譯碼
for( ; ReadBit<InLength*8; ){
//判決器：輸出漢明距離最小的幸存路徑的高32比特，有多個最小時輸出任意一個
if(OutBit == Path_Length){
//輸出最小路徑的高32比特信息序列
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>24);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>16);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>8);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32);
OutBit = 32;
}
//接收序列各個時刻的循環
//每個時刻輸出2比特，和接收序列對應時刻的碼組比較得到漢明距離
NowCod = InBuf[ReadBit/8] >> (6-ReadBit%8);//從接收序列中取出一個碼組
NowCod = NowCod & 0x03;
ReadBit += 2;
//累加器：進行距離累加
for(j=0; j<Path_Num; j++){
Now_States = char(Survivor_Save[j].L_m32 & 0x3f);
Survivor_Temp[j].Sum_d = Survivor_Save[j].Sum_d +
WeightInt(NowCod ^ Branch_Tab[Now_States][0]);
Survivor_Temp[j].H_m32 = Survivor_Save[j].H_m32<<1 |
Survivor_Save[j].L_m32>>31;
Survivor_Temp[j].L_m32 = Survivor_Save[j].L_m32<<1;
Survivor_Temp[j+Path_Num].Sum_d = Survivor_Save[j].Sum_d +
WeightInt(NowCod ^ Branch_Tab[Now_States][1]);
Survivor_Temp[j+Path_Num].H_m32 = Survivor_Save[j].H_m32<<1 |
Survivor_Save[j].L_m32>>31;
Survivor_Temp[j+Path_Num].L_m32 = (Survivor_Save[j].L_m32<<1) | 1;
}
//比較器：比較各條路徑的距離，保留相對較小的Path_Num條
//用選擇法對Survivor_Temp[].Sum_d按由小到大排序
for(i=0; i<Path_Num; i++){
for(j=i+1; j<2*Path_Num; j++){
if(Survivor_Temp[j].Sum_d < Survivor_Temp[i].Sum_d){
Temp_d = Survivor_Temp[i].Sum_d;
Temp_Hm = Survivor_Temp[i].H_m32;
Temp_Lm = Survivor_Temp[i].L_m32;
Survivor_Temp[i].Sum_d = Survivor_Temp[j].Sum_d;
Survivor_Temp[i].H_m32 = Survivor_Temp[j].H_m32;
Survivor_Temp[i].L_m32 = Survivor_Temp[j].L_m32;
Survivor_Temp[j].Sum_d = Temp_d;
Survivor_Temp[j].H_m32 = Temp_Hm;
Survivor_Temp[j].L_m32 = Temp_Lm;
}
}
}
//將較小的Path_Num條存入幸存路徑結構緩存
for(i=0; i<Path_Num; i++){
Survivor_Save[i].Sum_d = Survivor_Temp[i].Sum_d;
Survivor_Save[i].H_m32 = Survivor_Temp[i].H_m32;
Survivor_Save[i].L_m32 = Survivor_Temp[i].L_m32;
}
OutBit++;
}
//第三步：對數據尾部的處理，
//輸出漢明距離最小的幸存路徑的OutBit個比特(位權較低的OutBit個)，有多個最小的輸出任意一個
if(OutBit == 64){
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>24);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>16);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32>>8);
OutBuf[WriteByte++] = char(Survivor_Save[0].H_m32);
OutBuf[WriteByte++] = char(Survivor_Save[0].L_m32>>24);
OutBuf[WriteByte++] = char(Survivor_Save[0].L_m32>>16);
OutBuf[WriteByte++] = char(Survivor_Save[0].L_m32>>8);
OutBuf[WriteByte++] = char(Survivor_Save[0].L_m32);
}
else{
if(OutBit > 32){
Temp_Hm = (Survivor_Save[0].H_m32<<(64-OutBit)) | (Survivor_Save[0].L_m32>>(OutBit-32));
OutBuf[WriteByte++] = char(Temp_Hm>>24);
OutBuf[WriteByte++] = char(Temp_Hm>>16);
OutBuf[WriteByte++] = char(Temp_Hm>>8);
OutBuf[WriteByte++] = char(Temp_Hm);
OutBit -= 32;
}
Temp_Lm = Survivor_Save[0].L_m32 << (32-OutBit);
while(OutBit > 0){
OutBuf[WriteByte++] = char(Temp_Lm>>24);
Temp_Lm = Temp_Lm << 8;
OutBit -= 8;
}
}
//第四步：如果處理的是連續數據，要將較小幸存路徑的漢明距離縮小，避免溢出
/*for(i=1; i<Path_Num; i++){
if((Survivor_Save[i].Sum_d - Survivor_Save[0].Sum_d) > Path_Length)
Survivor_Save[i].Sum_d = Path_Length;
else
Survivor_Save[i].Sum_d -= Survivor_Save[0].Sum_d;
}
Survivor_Save[0].Sum_d = 0;
//*/
//維特比譯碼結束
return WriteByte;
}
//---------------------------------------------------------------------------
int CViterbi_216::Encode_216(unsigned char * InBuf, int InLength, unsigned char * OutBuf, int Now_State)
{
int ReadBit;
int ReadByte;
int WriteBit;
unsigned char Now_m;
unsigned char Now_Encode;
for(ReadByte=0,WriteBit=0; ReadByte<InLength; ReadByte++){
for(ReadBit=0; ReadBit<8; ReadBit++){
Now_m = InBuf[ReadByte]>>(7-ReadBit);
Now_m = Now_m & 0x01;
Now_Encode = Branch_Tab[Now_State][Now_m];
Now_State = Now_State<<1 | Now_m;
Now_State = Now_State & 0x3f;
OutBuf[WriteBit/8] = (OutBuf[WriteBit/8]<<2) | Now_Encode;
WriteBit += 2;
}
}
if(WriteBit != 2*8*InLength)
return 0xff;
return Now_State;
}
//---------------------------------------------------------------------------
int WeightInt(int x)
{
int countx = 0;
while(x)
{
countx ++;
x = x&(x-1);
}
return countx;
}
//每次將最低位的“1”去掉
//---------------------------------------------------------------------------
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -