一,Nalu解析
首先来介绍下h265(HEVC)nal单元头,与h264的nal层相比,h265的nal unit header有两个字节构成,如下图所示
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+ -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| F | Type | LayerId | TID |
+------------ - +---------------- - +
其语法如下表中的定义:
nal_unit_header( ) { |
Descriptor |
forbidden_zero_bit |
f(1) |
nal_unit_type |
u(6) |
nuh_reserved_zero_6bits |
u(6) |
nuh_temporal_id_plus1 |
u(3) |
} |
|
在文件中查找00 00 00 01NALU头,发现在有6种开头分别为:
再根据H265的NALU类型定义分析,
00 00 00 01 40 01 的nuh_unit_type的值为 32, 语义为视频参数集 VPS
00 00 00 01 42 01 的nuh_unit_type的值为 33, 语义为序列参数集 SPS
00 00 00 01 44 01 的nuh_unit_type的值为 34, 语义为图像参数集 PPS
00 00 00 01 4E 01 的nuh_unit_type的值为 39, 语义为补充增强信息 SEI
00 00 00 01 26 01 的nuh_unit_type的值为 19, 语义为可能有RADL图像的IDR图像的SS编码数据 IDR
00 00 00 01 02 01 的nuh_unit_type的值为1, 语义为被参考的后置图像,且非TSA、非STSA的SS编码数据
在编码过程中,从编码器获取码流的时候,1、2、3、4、5是在一帧数据当中。相当于H264的I帧。
Nalu Type的定义
二, SPS解析
1、重新定义类型
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef unsigned long uint32;2、定义Sps 需要的相关参数
struct vc_params_t
{
LONG width,height;
DWORD profile, level;
DWORD nal_length_size;
void clear()
{
memset(this, 0, sizeof(*this));
}
};
3、定义网络抽象层Nal类
class NALBitstream
{
public:
NALBitstream() : m_data(NULL), m_len(0), m_idx(0), m_bits(0), m_byte(0), m_zeros(0)
{
};
NALBitstream(void * data, int len)
{
Init(data, len);
};
void Init(void * data, int len)
{
m_data = (LPBYTE)data;
m_len = len;
m_idx = 0;
m_bits = 0;
m_byte = 0;
m_zeros = 0;
};
BYTE GetBYTE()
{
if ( m_idx >= m_len )
return 0;
BYTE b = m_data[m_idx++];
if ( b == 0 )
{
m_zeros++;
if ( (m_idx < m_len) && (m_zeros == 2) && (m_data[m_idx] == 0x03) )
{
m_idx++;
m_zeros=0;
}
}
else m_zeros = 0;
return b;
};
UINT32 GetBit()
{
if (m_bits == 0)
{
m_byte = GetBYTE();
m_bits = 8;
}
m_bits--;
return (m_byte >> m_bits) & 0x1;
};
UINT32 GetWord(int bits)
{
UINT32 u = 0;
while ( bits > 0 )
{
u <<= 1;
u |= GetBit();
bits--;
}
return u;
};
UINT32 GetUE()
{
int zeros = 0;
while (m_idx < m_len && GetBit() == 0 ) zeros++;
return GetWord(zeros) + ((1 << zeros) - 1);
};
INT32 GetSE()
{
UINT32 UE = GetUE();
bool positive = UE & 1;
INT32 SE = (UE + 1) >> 1;
if ( !positive )
{
SE = -SE;
}
return SE;
};
private:
LPBYTE m_data;
int m_len;
int m_idx;
int m_bits;
BYTE m_byte;
int m_zeros;
};
bool ParseSequenceParameterSet(BYTE* data,int size, vc_params_t& params)
{
if (size < 20)
{
return false;
}
NALBitstream bs(data, size);
// seq_parameter_set_rbsp()
bs.GetWord(4);// sps_video_parameter_set_id
int sps_max_sub_layers_minus1 = bs.GetWord(3);
if (sps_max_sub_layers_minus1 > 6)
{
return false;
}
bs.GetWord(1);
{
bs.GetWord(2);
bs.GetWord(1);
params.profile = bs.GetWord(5);
bs.GetWord(32);//
bs.GetWord(1);//
bs.GetWord(1);//
bs.GetWord(1);//
bs.GetWord(1);//
bs.GetWord(44);//
params.level = bs.GetWord(8);// general_level_idc
uint8 sub_layer_profile_present_flag[6] = {0};
uint8 sub_layer_level_present_flag[6] = {0};
for (int i = 0; i < sps_max_sub_layers_minus1; i++) {
sub_layer_profile_present_flag[i]= bs.GetWord(1);
sub_layer_level_present_flag[i]= bs.GetWord(1);
}
if (sps_max_sub_layers_minus1 > 0)
{
for (int i = sps_max_sub_layers_minus1; i < 8; i++) {
uint8 reserved_zero_2bits = bs.GetWord(2);
}
}
for (int i = 0; i < sps_max_sub_layers_minus1; i++)
{
if (sub_layer_profile_present_flag[i]) {
bs.GetWord(2);
bs.GetWord(1);
bs.GetWord(5);/
bs.GetWord(32);
bs.GetWord(1);
bs.GetWord(1);
bs.GetWord(1);
bs.GetWord(1);
bs.GetWord(44);
}
if (sub_layer_level_present_flag[i]) {
bs.GetWord(8);// sub_layer_level_idc[i]
}
}
}
uint32 sps_seq_parameter_set_id= bs.GetUE();
if (sps_seq_parameter_set_id > 15) {
return false;
}
uint32 chroma_format_idc = bs.GetUE();
if (sps_seq_parameter_set_id > 3) {
return false;
}
if (chroma_format_idc == 3) {
bs.GetWord(1);//
}
params.width = bs.GetUE(); // pic_width_in_luma_samples
params.height = bs.GetUE(); // pic_height_in_luma_samples
if (bs.GetWord(1)) {
bs.GetUE();
bs.GetUE();
bs.GetUE();
bs.GetUE();
}
uint32 bit_depth_luma_minus8= bs.GetUE();
uint32 bit_depth_chroma_minus8= bs.GetUE();
if (bit_depth_luma_minus8 != bit_depth_chroma_minus8) {
return false;
}
//...
return true;
}
int _tmain(int argc, _TCHAR* argv[])
{
vc_params_t params = { 0 };
BYTE Sps[41] = { 0X42,0X01,0X01,0X01,0X60,0X00,0X00,0X03,0X00,0X80,0X00,0X00,0X03,0X00,0X00,
0X03,0X00,0X5D,0XA0,0X02,0X80, 0X80,0X2D,0X16,0X59,0X5E,0X49,0X32,0XB8,0X04,0X00,0X00,0X03,
0X00,0X04,0X00,0X00,0X03,0X00,0X64,0X20 };
ParseSequenceParameterSet(Sps, 41, params);
printf("%d-%d-%d\n", params.width, params.height, params.level);
system("pause");
return 0;
}