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h264_nal.cpp
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h264_nal.cpp
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#include "h264_nal.h"
#include <memory.h>
static int h264_get_nal(const unsigned char* buf,const unsigned int size,h264_nalu* nalu,bool lastOne = false);
/**
* 查找startcode
*/
static int FindStartCode3 (const unsigned char *Buf){
if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=1) return 0; //0x000001?
else return 1;
}
/**
* 查找startcode,
*/
static int FindStartCode4 (const unsigned char *Buf){
if(Buf[0]!=0 || Buf[1]!=0 || Buf[2] !=0 || Buf[3] !=1) return 0;//0x00000001?
else return 1;
}
int NaluStartCodeLen(const unsigned char* pucBuf){
int startCode = 3;
if(pucBuf[0] == 0 && pucBuf[1] == 0 &&pucBuf[2] == 0 && pucBuf[3] == 1){
startCode = 4;
}
else if(pucBuf[0] == 0 && pucBuf[1] == 0 &&pucBuf[2] == 1 ){
startCode = 3;
}
else{
startCode = 0;
}
return startCode;
}
bool H264Reader::ReadNalu(uint8_t *nal, int *len){
h264_nalu nalu;
bool ret = ReadNalu(&nalu);
if(ret == false){
return false;
}
*len = nalu.nal_len;
memcpy(nal,nalu.buf,nalu.nal_len);
return true;
}
bool H264Reader::ReadNaluWithStartCode(uint8_t *nal, int *len){
h264_nalu nalu;
bool ret = ReadNalu(&nalu);
if(ret == false){
return false;
}
if(nalu.start_code_len == 3){
nal[0] = 0;nal[1] = 0;
nal[2] = 1;
}
else{
nal[0] = 0;nal[1] = 0;
nal[2] = 0;nal[3] = 1;
}
*len = nalu.nal_len + nalu.start_code_len;
memcpy(nal + nalu.start_code_len,nalu.buf,nalu.nal_len);
return true;
}
bool H264Reader::ReadNalu(h264_nalu *nalu){
bool eof = true;
while (true) {
if(ReadDataFromFile()){
eof = false;
}
else{
eof = true;
}
size_t dataLen = end - start;
// 文件已经读完,buffer也没有数据,那么返回false
if(eof && dataLen == 0){
return false;
}
int ret = h264_get_nal(start,dataLen,nalu);
// 读取一个nalu失败,可能是数据不够造成的
if(ret == 0){
// 判断一下是不是已经到文件末尾了,那么剩下的数据全部作为一个nalu处理
if(eof){
ret = h264_get_nal(start,(end - start),nalu,true);
start = end;
if(ret == 0){
return false;
}
else{
return true;
}
}
else{
// 文件中还有数据,那么继续把数据读取到buffer中
continue;
}
}
else{
// 读取成功
start += ret;
return true;
}
}
}
int H264Reader::ReadDataFromFile(){
if(feof(fp_in)){
return 0;
}
// 如果end位置已经指向buffer末尾,那么把数据往前移动
if(end == buf + capacity){
size_t dataLen = end - start;
memmove(buf,start,dataLen);
start = buf;
end = start + dataLen;
}
// buffer剩余的空间
size_t leftLen = capacity - (end - start);
// 如果buffer剩余的空间大于4096,那么尝试读取4096字节的数据
// 否则就把buffer剩下的空间读满
size_t tryReadLen = leftLen;
if(leftLen > 1024 * 4){
tryReadLen = 1024 * 4;
}
else{
tryReadLen = leftLen;
}
// 实际读取到的数据长度
int realReadLen = fread(end,1,tryReadLen,fp_in);
if(realReadLen < 0){
return -1;
}
end += realReadLen;
return realReadLen;
}
void H264Reader_Test(const char* srcFileName,const char* dstFileName){
FILE* fp_src = fopen(srcFileName,"rb");
FILE* fp_dst = fopen(dstFileName,"wb");
H264Reader reader(fp_src);
h264_nalu nalu;
while (reader.ReadNalu(&nalu)) {
if(nalu.start_code_len == 3){
fputc(0,fp_dst);
fputc(0,fp_dst);
fputc(1,fp_dst);
}
else{
fputc(0,fp_dst);
fputc(0,fp_dst);
fputc(0,fp_dst);
fputc(1,fp_dst);
}
fwrite(nalu.buf,1,nalu.nal_len,fp_dst);
}
fflush(fp_dst);
fclose(fp_dst);
fclose(fp_src);
}
static int h264_get_nal(const unsigned char* buf,const unsigned int size,h264_nalu* nalu,bool lastOne){
int i = 0;
while(i<size)
{
// 寻找nalu的startcode
int startCodeLen = 0;
if((i + 2 < size) && FindStartCode3(&buf[i]) ){
startCodeLen = 3;
}
else if((i + 3 < size) && FindStartCode4(&buf[i])){
startCodeLen = 4;
}
else{
++i;
continue;
}
// 此时i指向startcode的第一个字节
nalu->start_code_len = startCodeLen;
// 此时i指向nalu的头部
i += startCodeLen;
// begin指向nalu的头部
int begin = i;
int end = i;
int nextStartCodeLen = 0;
// 如果不是最后一个nalu,那么需要找到下一个nalu的startcode才能确定nalu的长度
if(lastOne == false){
// 找到下一个nalu的startcode,如果找到,那么end指向下一个nalu的startcode
while (end<size){
nextStartCodeLen = 0;
if((end + 2 < size) && FindStartCode3(&buf[end]) ){
nextStartCodeLen = 3;
break;
}
else if((end + 3 < size) && FindStartCode4(&buf[end])){
nextStartCodeLen = 4;
break;
}
else{
++end;
continue;
}
}
// 如果没有找到,表示buf中的数据不够(因为已经明确指示这不是最后一个nalu),返回false
if(nextStartCodeLen == 0){
return 0;
}
}
else{
// 如果是最后一个nalu,那么剩下的数据全部属于一个nalu
end = size;
}
int dataLen = end- begin;
nalu->nal_unit_type = ( EnNaluType)(buf[begin]&0x1f);
nalu->nal_ref_idc = ( EnNaluPriority)(buf[begin] & 0x60);
nalu->nal_header = buf[begin];
nalu->nal_len = dataLen;
memcpy(nalu->buf,&buf[begin],nalu->nal_len);
return (end);
}
return 0;
}