从H264码流中获取视频宽高 (SPS帧)

获取.h264视频宽高的方法

花了2个通宵终于搞定。（后面附上完整代码）

http://write.blog.csdn.net/postedit/7852406

图像的高和宽在H264的SPS帧中。
在H264码流中，都是以"0x00 0x00 0x01"或者"0x00 0x00 0x00 0x01"为开始码的,找到开始码之后,使用开始码之后的第一个字节的低5位判断是否为7(sps)，等于7表示该帧就是SPS帧，从该帧就可以解析出高和宽，SPS是个结构体，里面有两个成员：pic_width_in_mbs_minus1，pic_height_in_map_units_minus_1，分别表示图像的宽和高，以宏块（16x16）为单位的值减1，因此，实际的宽为 (pic_width_in_mbs_minus1+1)*16，高为 (pic_height_in_map_units_minus_1+1)*16

http://write.blog.csdn.net/postedit/7852406

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;
}


bool h264_decode_seq_parameter_set(BYTE * buf,UINT nLen,int &Width,int &Height)
{
UINT StartBit=0; 
int forbidden_zero_bit=u(1,buf,StartBit);
int nal_ref_idc=u(2,buf,StartBit);
int nal_unit_type=u(5,buf,StartBit);
if(nal_unit_type==7)
{
int profile_idc=u(8,buf,StartBit);
int constraint_set0_flag=u(1,buf,StartBit);//(buf[1] & 0x80)>>7;
int constraint_set1_flag=u(1,buf,StartBit);//(buf[1] & 0x40)>>6;
int constraint_set2_flag=u(1,buf,StartBit);//(buf[1] & 0x20)>>5;
int constraint_set3_flag=u(1,buf,StartBit);//(buf[1] & 0x10)>>4;
int reserved_zero_4bits=u(4,buf,StartBit);
int level_idc=u(8,buf,StartBit);

int seq_parameter_set_id=Ue(buf,nLen,StartBit);

if( profile_idc == 100 || profile_idc == 110 ||
profile_idc == 122 || profile_idc == 144 )
{
int chroma_format_idc=Ue(buf,nLen,StartBit);
if( chroma_format_idc == 3 )
int residual_colour_transform_flag=u(1,buf,StartBit);
int bit_depth_luma_minus8=Ue(buf,nLen,StartBit);
int bit_depth_chroma_minus8=Ue(buf,nLen,StartBit);
int qpprime_y_zero_transform_bypass_flag=u(1,buf,StartBit);
int seq_scaling_matrix_present_flag=u(1,buf,StartBit);

int seq_scaling_list_present_flag[8];
if( seq_scaling_matrix_present_flag )
{
for( int i = 0; i < 8; i++ ) {
seq_scaling_list_present_flag[i]=u(1,buf,StartBit);
}
}
}
int log2_max_frame_num_minus4=Ue(buf,nLen,StartBit);
int pic_order_cnt_type=Ue(buf,nLen,StartBit);
if( pic_order_cnt_type == 0 )
int log2_max_pic_order_cnt_lsb_minus4=Ue(buf,nLen,StartBit);
else if( pic_order_cnt_type == 1 )
{
int delta_pic_order_always_zero_flag=u(1,buf,StartBit);
int offset_for_non_ref_pic=Se(buf,nLen,StartBit);
int offset_for_top_to_bottom_field=Se(buf,nLen,StartBit);
int num_ref_frames_in_pic_order_cnt_cycle=Ue(buf,nLen,StartBit);

int *offset_for_ref_frame=new int[num_ref_frames_in_pic_order_cnt_cycle];
for( int i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; i++ )
offset_for_ref_frame[i]=Se(buf,nLen,StartBit);
delete [] offset_for_ref_frame;
}
int num_ref_frames=Ue(buf,nLen,StartBit);
int gaps_in_frame_num_value_allowed_flag=u(1,buf,StartBit);
int pic_width_in_mbs_minus1=Ue(buf,nLen,StartBit);
int pic_height_in_map_units_minus1=Ue(buf,nLen,StartBit);

Width=(pic_width_in_mbs_minus1+1)*16;
Height=(pic_height_in_map_units_minus1+1)*16;

return true;
}
else
return false;
}




void CCommDlg::OnOK() 
{
CString  str;
//数据必须把H264的头0x000001去掉
BYTE bytes[11]={0x67,0x64,0x08,0x1F,0xAC,0x34,0xC1,0x08,0x28,0x0F,0x64};
UINT startbit=0;
int Width,Height;
if (h264_decode_seq_parameter_set(bytes,11,Width,Height))
{
str.Format("%d-%d",Width,Height);


AfxMessageBox(str);
}
}