H264解码SPS获取宽高和帧率
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- #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
- */
- void de_emulation_prevention(BYTE* buf,unsigned int* buf_size)
- {
- int i=0,j=0;
- BYTE* tmp_ptr=NULL;
- unsigned int tmp_buf_size=0;
- int val=0;
- tmp_ptr=buf;
- tmp_buf_size=*buf_size;
- for(i=0;i<(tmp_buf_size-2);i++)
- {
- //check for 0x000003
- val=(tmp_ptr[i]^0x00) +(tmp_ptr[i+1]^0x00)+(tmp_ptr[i+2]^0x03);
- if(val==0)
- {
- //kick out 0x03
- for(j=i+2;j<tmp_buf_size-1;j++)
- tmp_ptr[j]=tmp_ptr[j+1];
- //and so we should devrease bufsize
- (*buf_size)--;
- }
- }
- }
- /**
- * 解码SPS,获取视频图像宽、高和帧率信息
- *
- * @param buf SPS数据内容
- * @param nLen SPS数据的长度
- * @param width 图像宽度
- * @param height 图像高度
- * @成功则返回true , 失败则返回false
- */
- bool h264_decode_sps(BYTE * buf,unsigned int nLen,int &width,int &height,int &fps)
- {
- UINT StartBit=0;
- fps=0;
- de_emulation_prevention(buf,&nLen);
- 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;
- int frame_mbs_only_flag=u(1,buf,StartBit);
- if(!frame_mbs_only_flag)
- int mb_adaptive_frame_field_flag=u(1,buf,StartBit);
- int direct_8x8_inference_flag=u(1,buf,StartBit);
- int frame_cropping_flag=u(1,buf,StartBit);
- if(frame_cropping_flag)
- {
- int frame_crop_left_offset=Ue(buf,nLen,StartBit);
- int frame_crop_right_offset=Ue(buf,nLen,StartBit);
- int frame_crop_top_offset=Ue(buf,nLen,StartBit);
- int frame_crop_bottom_offset=Ue(buf,nLen,StartBit);
- }
- int vui_parameter_present_flag=u(1,buf,StartBit);
- if(vui_parameter_present_flag)
- {
- int aspect_ratio_info_present_flag=u(1,buf,StartBit);
- if(aspect_ratio_info_present_flag)
- {
- int aspect_ratio_idc=u(8,buf,StartBit);
- if(aspect_ratio_idc==255)
- {
- int sar_width=u(16,buf,StartBit);
- int sar_height=u(16,buf,StartBit);
- }
- }
- int overscan_info_present_flag=u(1,buf,StartBit);
- if(overscan_info_present_flag)
- int overscan_appropriate_flagu=u(1,buf,StartBit);
- int video_signal_type_present_flag=u(1,buf,StartBit);
- if(video_signal_type_present_flag)
- {
- int video_format=u(3,buf,StartBit);
- int video_full_range_flag=u(1,buf,StartBit);
- int colour_description_present_flag=u(1,buf,StartBit);
- if(colour_description_present_flag)
- {
- int colour_primaries=u(8,buf,StartBit);
- int transfer_characteristics=u(8,buf,StartBit);
- int matrix_coefficients=u(8,buf,StartBit);
- }
- }
- int chroma_loc_info_present_flag=u(1,buf,StartBit);
- if(chroma_loc_info_present_flag)
- {
- int chroma_sample_loc_type_top_field=Ue(buf,nLen,StartBit);
- int chroma_sample_loc_type_bottom_field=Ue(buf,nLen,StartBit);
- }
- int timing_info_present_flag=u(1,buf,StartBit);
- if(timing_info_present_flag)
- {
- int num_units_in_tick=u(32,buf,StartBit);
- int time_scale=u(32,buf,StartBit);
- fps=time_scale/num_units_in_tick;
- int fixed_frame_rate_flag=u(1,buf,StartBit);
- if(fixed_frame_rate_flag)
- {
- fps=fps/2;
- }
- }
- }
- return true;
- }
- else
- return false;
- }
timing_info_present_flag等于0表示num_units_in_tick，time_scale和fixed_frame_rate_flag在比特流中不存在。
因此，当timing_info_present_flag等于0时，无法得到码率，bool h264_decode_sps(BYTE * buf,unsigned int nLen,int &width,int &height,int &fps)参数fps返回值为0，可据此设置一个默认帧率。
参考链接：http://blog.csdn.net/qq_27727131/article/details/51799663
转自：http://blog.csdn.net/caoshangpa/article/details/53083410阅读全文
