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h264 sps中解析宽高

h264 sps中解析宽高

作者: 爱吃花栗鼠的猫 | 来源:发表于2017-11-28 14:29 被阅读198次

    代码是借鉴的别人的

    #include <cstdint>
    #include <cmath>
    
    uint32_t Ue(uint8_t *pBuff, uint32_t nLen, uint32_t &nStartBit)
    {
        //计算0bit的个数
        uint32_t 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
        uint32_t dwRet = 0;
        for (uint32_t i=0; i<nZeroNum; i++)
        {
            dwRet <<= 1;
            if (pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8)))
            {
                dwRet += 1;
            }
            nStartBit++;
        }
        return (1 << nZeroNum) - 1 + dwRet;
    }
    
    
    int Se(uint8_t *pBuff, uint32_t nLen, uint32_t &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;
    
    
    }
    
    
    uint32_t u(uint32_t BitCount,uint8_t * buf,uint32_t &nStartBit)
    {
        uint32_t dwRet = 0;
        for (uint32_t 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(uint8_t * buf,uint32_t nLen,int &Width,int &Height)
    {
        uint32_t 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;
    }
    
    
    
    
    int main()
    {
    //数据必须把H264的头0x000001去掉
    //    uint8_t str[11]={0x67,0x64,0x08,0x1F,0xAC,0x34,0xC1,0x08,0x28,0x0F,0x64};
        uint8_t str[25] = {0x67,0x64,0x00,0x1F,0xAC,0x2C,0xAC,0x05,0x00,0x5B,0xB0,0x11,0x00,0x00,0x03,0x03,0xE8,0x00,0x00,0xC3,0x50,0x8F,0x1C,0x31,0x38};
    
        uint32_t startbit=0;
        int Width,Height;
        if (h264_decode_seq_parameter_set(str,11,Width,Height))
        {
    
        }
    
        return 0;
    }
    

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