H264解码SPS获取宽高和帧率

来源：互联网发布：iap15w413as数据手册编辑：程序博客网时间：2024/05/22 03:39
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 */ 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)--;        }    }    return;}/** * 解码SPS,获取视频图像宽、高信息  * * @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1 , 失败则返回0 */ int 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/(2*num_units_in_tick);            }        }        return true;    }    else        return false;}
阅读全文
0 0