sps定义如下：
解析如下：
分辨率：
宽高可从SPS字段计算得到，公式如下：Width = (pic_width_in_mbs_minus1+1)*16;
Height = (pic_height_in_map_units_minus1+1)*16;
但以上是针对宽高是16的整数倍的情况，当不是16整数倍
时，frame_cropping_flag值为1，frame_mbs_only_flag为1，公式如下：
(也可以认为统一使用下面的公式)
width = ((pic_width_in_mbs_minus1 +1)*16) - frame_crop_left_offset*2 - frame_crop_right_offset*2;
height= ((2 - frame_mbs_only_flag)* (pic_height_in_map_units_minus1 +1) * 16) - (frame_crop_top_offset * 2) - (frame_crop_bottom_offset * 2);
以上公式是一年多以前在网上找的，仔细看手册，上面的公式有局限性。根据H264
手册Table6-1及7.4.2.1.1，参考mkvtoolnix代码，比如稳妥的计算方法如下：
// 宽高计算公式
width = (sps->pic_width_in_mbs_minus1+1) * 16;
height = (2 - sps->frame_mbs_only_flag)* (sps->pic_height_in_map_units_minus1 +1) * 16);
if(sps->frame_cropping_flag)
{
unsigned int crop_unit_x;
unsigned int crop_unit_y;
if (0 == sps->chroma_format_idc) // monochrome
{
crop_unit_x = 1;
crop_unit_y = 2 - sps->frame_mbs_only_flag;
}
else if (1 == sps->chroma_format_idc) // 4:2:0
{
crop_unit_x = 2;
crop_unit_y = 2 * (2 - sps->frame_mbs_only_flag);
}
else if (2 == sps->chroma_format_idc) // 4:2:2
{
crop_unit_x = 2;
crop_unit_y = 2 - sps->frame_mbs_only_flag;
}
else // 3 == sps.chroma_format_idc // 4:4:4
{
crop_unit_x = 1;
crop_unit_y = 2 - sps->frame_mbs_only_flag;
}
width -= crop_unit_x * (sps->frame_crop_left_offset + sps->frame_crop_right_offset);
height -= crop_unit_y * (sps->frame_crop_top_offset + sps->frame_crop_bottom_offset);
}
*****************-----------------哥伦布编码-----------**************************
上面的有3种数据结构：u(1),ue(v),se(v), （转自https://blog.csdn.net/u012188065/article/details/53590641）
下面分别介绍：
u(1) :为一个字节取出前1位
ue(v) 为无符号指数哥伦布熵编码
编码过程如下：
对 4 进行无符号指数哥伦布熵编码
1、将4加1(为5)转换为最小的二进制序列即 101 (此是M=3)
2、此二进制序列前面补充M-1即两个0
3、得出的4的无符号指数哥伦布熵编码的序列为 00101
解码过程如下：
如对 00101进行无符号指数哥伦布熵解码
1、获取开头连续的N个0， 此时N = 2
2、再向后读取N+1位的值,即 101,为5
3、 5 - 1 =4 获取其解码后码值
se(v) 为有符号指数哥伦布熵编码
编码过程如下：
如对4进行有符号指数哥伦布熵编码
1、4的绝对值转为最小二进制序列，即 100 (此时M = 3)
2、后面补充符号位，0 即 1000
3、前面补充M个0， 即 0001000
解码过程如下：
如对二进制序列 0001000 进行有符号指数哥伦布熵解码
1、获取开头连续的N个0， 此时N = 3
2、再获取N为数值,即 100 即为4
3、获取最后的符号位，0，即为正值
4、故此序列解码后的码值为4
示例二：
编码
如对-15进行有符号指数哥伦布熵编码
1、-7的绝对值转为最小二进制序列,即 1111 (此时M = 4)
2、后面补充符号位，1，即 11111
3、前面补充M个0,即 000011111
解码：
如对二进制序列 000011111 进行有符号指数哥伦布熵解码
1、获取开头连续的N个0， 此时N = 4
2、再获取N为数值,即 1111 即为15
3、获取最后的符号位，1，即为负值
4、故此序列解码后的码值为-15
****************************代码实现*****************************************
U（n）数据类型的实现
static int U(int iBitCount, byte[] bData, ref int iStartBit)
{
int iRet = 0;
for(int i =0;i<iBitCount;i++)
{
iRet = iRet << 1;
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8))))
{
iRet += 1;
}
iStartBit++;
}
return iRet;
}Ue数据类型的解析
static UInt32 Ue(byte[] bData, ref int iStartBit)
{
//计算0bit的个数
int nZeroNum = 0;
while (iStartBit < bData.Length * 8)
{
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8)))) //&:按位与，%取余
{
break;
}
nZeroNum++;
iStartBit++;
}
nZeroNum = nZeroNum + 1;
//计算结果
UInt32 dwRet = 0;
for (UInt32 i = 0; i < nZeroNum; i++)
{
dwRet <<= 1;
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8))))
{
dwRet += 1;
}
iStartBit++;
}
return dwRet-1;
}Se数据类型的解析
static Int32 Se(byte[] bData, ref int iStartBit)
{
//计算0bit的个数
int nZeroNum = 0;
while (iStartBit < bData.Length * 8)
{
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8)))) //&:按位与，%取余
{
break;
}
nZeroNum++;
iStartBit++;
}
//计算结果
Int32 dwRet = 0;
for (UInt32 i = 0; i < nZeroNum; i++)
{
dwRet <<= 1;
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8))))
{
dwRet += 1;
}
iStartBit++;
}
if ((0x80 >> (iStartBit % 8)) == (bData[iStartBit / 8] & (0x80 >> (iStartBit % 8))))
{
dwRet = 0-dwRet;
}
iStartBit++;
return dwRet;
}
sps解析出长和宽如下：
public static bool H264_decode_sps(byte[] bData, ref int width, ref int height)
{
int StartBit = 0;
int forbidden_zero_bit = U(1, bData, ref StartBit);
int nal_ref_idc = U(2, bData, ref StartBit);
int nal_unit_type = U(5, bData, ref StartBit);
if (nal_unit_type == 7)
{
int profile_idc = U(8, bData, ref StartBit);
int constraint_set0_flag = U(1, bData, ref StartBit);//(buf[1] & 0x80)>>7;
int constraint_set1_flag = U(1, bData, ref StartBit);//(buf[1] & 0x40)>>6;
int constraint_set2_flag = U(1, bData, ref StartBit);//(buf[1] & 0x20)>>5;
int constraint_set3_flag = U(1, bData, ref StartBit);//(buf[1] & 0x10)>>4;
int reserved_zero_4bits = U(4, bData, ref StartBit);
int level_idc = U(8, bData, ref StartBit);
UInt32 seq_parameter_set_id = Ue(bData, ref StartBit);
UInt32 chroma_format_idc = 0;
if (profile_idc == 100 || profile_idc == 110 ||
profile_idc == 122 || profile_idc == 144)
{
chroma_format_idc = Ue(bData, ref StartBit);
if (chroma_format_idc == 3)
{
int residual_colour_transform_flag = U(1, bData, ref StartBit);
}
UInt32 bit_depth_luma_minus8 = Ue(bData, ref StartBit);
UInt32 bit_depth_chroma_minus8 = Ue(bData, ref StartBit);
int qpprime_y_zero_transform_bypass_flag = U(1, bData, ref StartBit);
int seq_scaling_matrix_present_flag = U(1, bData, ref StartBit);
int[] seq_scaling_list_present_flag = new int[8];
if (1 == seq_scaling_matrix_present_flag)
{
for (int i = 0; i < 8; i++)
{
seq_scaling_list_present_flag[i] = U(1, bData, ref StartBit);
}
}
}
UInt32 log2_max_frame_num_minus4 = Ue(bData, ref StartBit);
UInt32 pic_order_cnt_type = Ue(bData, ref StartBit);
if (pic_order_cnt_type == 0)
{
UInt32 log2_max_pic_order_cnt_lsb_minus4 = Ue(bData, ref StartBit);
}
else if (pic_order_cnt_type == 1)
{
int delta_pic_order_always_zero_flag = U(1, bData, ref StartBit);
int offset_for_non_ref_pic = Se(bData, ref StartBit);
int offset_for_top_to_bottom_field = Se(bData, ref StartBit);
UInt32 num_ref_frames_in_pic_order_cnt_cycle = Ue(bData, ref 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(bData, ref StartBit);
}
UInt32 num_ref_frames = Ue(bData, ref StartBit);
int gaps_in_frame_num_value_allowed_flag = U(1, bData, ref StartBit);
UInt32 pic_width_in_mbs_minus1 = Ue(bData, ref StartBit);
UInt32 pic_height_in_map_units_minus1 = Ue(bData, ref StartBit);
int frame_mbs_only_flag = U(1, bData, ref StartBit);
if (0 == frame_mbs_only_flag)
{
int mb_adaptive_frame_field_flag = U(1, bData, ref StartBit);
}
int direct_8x8_inference_flag = U(1, bData, ref StartBit);
int frame_cropping_flag = U(1, bData, ref StartBit);
UInt32 frame_crop_left_offset = 0;
UInt32 frame_crop_right_offset = 0;
UInt32 frame_crop_top_offset = 0;
UInt32 frame_crop_bottom_offset = 0;
if (1 == frame_cropping_flag)
{
frame_crop_left_offset = Ue(bData, ref StartBit);
frame_crop_right_offset = Ue(bData, ref StartBit);
frame_crop_top_offset = Ue(bData, ref StartBit);
frame_crop_bottom_offset = Ue(bData, ref StartBit);
}
int vui_parameter_present_flag = U(1, bData, ref StartBit);
if (1 == vui_parameter_present_flag)
{
int aspect_ratio_info_present_flag = U(1, bData, ref StartBit);
if (1 == aspect_ratio_info_present_flag)
{
int aspect_ratio_idc = U(8, bData, ref StartBit);
if (aspect_ratio_idc == 255)
{
int sar_width = U(16, bData, ref StartBit);
int sar_height = U(16, bData, ref StartBit);
}
}
int overscan_info_present_flag = U(1, bData, ref StartBit);
if (1 == overscan_info_present_flag)
{
int overscan_appropriate_flagu = U(1, bData, ref StartBit);
}
int video_signal_type_present_flag = U(1, bData, ref StartBit);
if (1 == video_signal_type_present_flag)
{
int video_format = U(3, bData, ref StartBit);
int video_full_range_flag = U(1, bData, ref StartBit);
int colour_description_present_flag = U(1, bData, ref StartBit);
if (1 == colour_description_present_flag)
{
int colour_primaries = U(8, bData, ref StartBit);
int transfer_characteristics = U(8, bData, ref StartBit);
int matrix_coefficients = U(8, bData, ref StartBit);
}
}
int chroma_loc_info_present_flag = U(1, bData, ref StartBit);
if (1 == chroma_loc_info_present_flag)
{
UInt32 chroma_sample_loc_type_top_field = Ue(bData, ref StartBit);
UInt32 chroma_sample_loc_type_bottom_field = Ue(bData, ref StartBit);
}
int timing_info_present_flag = U(1, bData, ref StartBit);
if (1 == timing_info_present_flag)
{
int num_units_in_tick = U(32, bData, ref StartBit);
int time_scale = U(32, bData, ref StartBit);
int fixed_frame_rate_flag = U(1, bData, ref StartBit);
}
}
// 宽高计算公式
width = ((int)pic_width_in_mbs_minus1 + 1) * 16;
height = (2 - (int)frame_mbs_only_flag) * ((int)pic_height_in_map_units_minus1 + 1) * 16;
if (1 == frame_cropping_flag)
{
int crop_unit_x;
int crop_unit_y;
if (0 == chroma_format_idc) // monochrome
{
crop_unit_x = 1;
crop_unit_y = 2 - frame_mbs_only_flag;
}
else if (1 == chroma_format_idc) // 4:2:0
{
crop_unit_x = 2;
crop_unit_y = 2 * (2 - frame_mbs_only_flag);
}
else if (2 == chroma_format_idc) // 4:2:2
{
crop_unit_x = 2;
crop_unit_y = 2 - frame_mbs_only_flag;
}
else // 3 == sps.chroma_format_idc // 4:4:4
{
crop_unit_x = 1;
crop_unit_y = 2 - frame_mbs_only_flag;
}
width -= crop_unit_x * ((int)frame_crop_left_offset + (int)frame_crop_right_offset);
height -= crop_unit_y * ((int)frame_crop_top_offset + (int)frame_crop_bottom_offset);
}
return true;
}
else
{
return false;
}
}为了便于大家学习和交流，采用vs2017开发 C#语言实现 工程地址如下：