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SpsDecode.cpp
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117 lines (104 loc) · 3.67 KB
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/*
* SpsDecode.h
*
* Created on: 2014-12-28
* Author: Administrator
*/
#include "SpsDecode.h"
char ue(char *pBuff, char nLen, char &nStartBit) {
//计算0bit的个数
char 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
int dwRet = 0;
for (char i = 0; i < nZeroNum; i++) {
dwRet <<= 1;
if (pBuff[nStartBit / 8] & (0x80 >> (nStartBit % 8))) {
dwRet += 1;
}
nStartBit++;
}
return (1 << nZeroNum) - 1 + dwRet;
}
int se(char *pBuff, char nLen, char &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;
}
int u(char BitCount, char * buf, char &nStartBit) {
int dwRet = 0;
for (char i = 0; i < BitCount; i++) {
dwRet <<= 1;
if (buf[nStartBit / 8] & (0x80 >> (nStartBit % 8))) {
dwRet += 1;
}
nStartBit++;
}
return dwRet;
}
bool h264_decode_sps(char* buf, int nLen, int &width, int &height) {
char 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;
}