H264解码SPS获取宽高和帧率

本篇文章讲述了如何解码SPS获取宽高和帧率信息。

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <math.h>

typedef  unsigned int UINT;
typedef  unsigned char BYTE;
typedef  unsigned long DWORD;

UINT Ue(BYTE *pBuff, UINT nLen, UINT &nStartBit)
{
    //计算0bit的个数
    UINT nZeroNum = 0;
    while (nStartBit < nLen * 8)
    {
        if (pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8))) //&:按位与，%取余
        {
            break;
        }
        nZeroNum++;
        nStartBit++;
    }
    nStartBit ++;


    //计算结果
    DWORD dwRet = 0;
    for (UINT i=0; i<nZeroNum; i++)
    {
        dwRet <<= 1;
        if (pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8)))
        {
            dwRet += 1;
        }
        nStartBit++;
    }
    return (1 << nZeroNum) - 1 + dwRet;
}


int Se(BYTE *pBuff, UINT nLen, UINT &nStartBit)
{
    int UeVal=Ue(pBuff,nLen,nStartBit);
    double k=UeVal;
    int nValue=ceil(k/2);//ceil函数：ceil函数的作用是求不小于给定实数的最小整数。ceil(2)=ceil(1.2)=cei(1.5)=2.00
    if (UeVal % 2==0)
        nValue=-nValue;
    return nValue;
}


DWORD u(UINT BitCount,BYTE * buf,UINT &nStartBit)
{
    DWORD dwRet = 0;
    for (UINT i=0; i<BitCount; i++)
    {
        dwRet <<= 1;
        if (buf[nStartBit / 8] & (0x80 >> (nStartBit % 8)))
        {
            dwRet += 1;
        }
        nStartBit++;
    }
    return dwRet;
}

/**
 * H264的NAL起始码防竞争机制 
 *
 * @param buf SPS数据内容
 *
 * @无返回值
 */</