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 = ;
     while (nStartBit < nLen * )
     {
         if (pBuff[nStartBit / ] & (0x80 >> (nStartBit % ))) //&:按位与，%取余
         {
             break;
         }
         nZeroNum++;
         nStartBit++;
     }
     nStartBit ++;

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

 int Se(BYTE *pBuff, UINT nLen, UINT &nStartBit)
 {

 int UeVal=Ue(pBuff,nLen,nStartBit);
 double k=UeVal;
 int nValue=ceil(k/);//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 % ==)
 nValue=-nValue;
      return nValue;

 }

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

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

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

 if( profile_idc ==  || profile_idc ==  ||
 profile_idc ==  || profile_idc ==  )
 {
 int chroma_format_idc=Ue(buf,nLen,StartBit);
 if( chroma_format_idc ==  )
 int residual_colour_transform_flag=u(,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(,buf,StartBit);
 int seq_scaling_matrix_present_flag=u(,buf,StartBit);

 int seq_scaling_list_present_flag[];
 if( seq_scaling_matrix_present_flag )
 {
 for( int i = ; i < ; i++ ) {
 seq_scaling_list_present_flag[i]=u(,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 ==  )
 int log2_max_pic_order_cnt_lsb_minus4=Ue(buf,nLen,StartBit);
 else if( pic_order_cnt_type ==  )
 {
 int delta_pic_order_always_zero_flag=u(,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 = ; 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(,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+)*;
 Height=(pic_height_in_map_units_minus1+)*;

 return true;
 }
 else
 return false;
 }

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

 AfxMessageBox(str);
 }
 }