h265 Nalu类型判断及 sps 数据解析

一时失言乱红尘 2022-03-11 07:28 1103阅读 0赞

[https://blog.csdn.net/machh/article/details/72190321][https_blog.csdn.net_machh_article_details_72190321]

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)

从图中可以看出hHEVC的nal包结构与h264有明显的不同，hevc加入了nal所在的时间层的ＩＤ，取去除了nal\_ref\_idc，此信息合并到了naltype中，  
通常情况下F为0，layerid为0, TID为1。

H265 帧类型判断：  
和264的&0x1f不同。265是 :  
int type = (code & 0x7E)>>1;

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

enum NalUnitType  
\{  
NAL\_UNIT\_CODED\_SLICE\_TRAIL\_N = 0, // 0  
NAL\_UNIT\_CODED\_SLICE\_TRAIL\_R, // 1  
  
NAL\_UNIT\_CODED\_SLICE\_TSA\_N, // 2  
NAL\_UNIT\_CODED\_SLICE\_TLA, // 3 // Current name in the spec: TSA\_R  
  
NAL\_UNIT\_CODED\_SLICE\_STSA\_N, // 4  
NAL\_UNIT\_CODED\_SLICE\_STSA\_R, // 5  
  
NAL\_UNIT\_CODED\_SLICE\_RADL\_N, // 6  
NAL\_UNIT\_CODED\_SLICE\_DLP, // 7 // Current name in the spec: RADL\_R  
  
NAL\_UNIT\_CODED\_SLICE\_RASL\_N, // 8  
NAL\_UNIT\_CODED\_SLICE\_TFD, // 9 // Current name in the spec: RASL\_R  
  
NAL\_UNIT\_RESERVED\_10,  
NAL\_UNIT\_RESERVED\_11,  
NAL\_UNIT\_RESERVED\_12,  
NAL\_UNIT\_RESERVED\_13,  
NAL\_UNIT\_RESERVED\_14,  
NAL\_UNIT\_RESERVED\_15, NAL\_UNIT\_CODED\_SLICE\_BLA, // 16 // Current name in the spec: BLA\_W\_LP  
NAL\_UNIT\_CODED\_SLICE\_BLA, // 16 // Current name in the spec: BLA\_W\_LP  
NAL\_UNIT\_CODED\_SLICE\_BLANT, // 17 // Current name in the spec: BLA\_W\_DLP  
NAL\_UNIT\_CODED\_SLICE\_BLA\_N\_LP, // 18  
NAL\_UNIT\_CODED\_SLICE\_IDR, // 19 // Current name in the spec: IDR\_W\_DLP  
NAL\_UNIT\_CODED\_SLICE\_IDR\_N\_LP, // 20  
NAL\_UNIT\_CODED\_SLICE\_CRA, // 21  
NAL\_UNIT\_RESERVED\_22,  
NAL\_UNIT\_RESERVED\_23,  
  
NAL\_UNIT\_RESERVED\_24,  
NAL\_UNIT\_RESERVED\_25,  
NAL\_UNIT\_RESERVED\_26,  
NAL\_UNIT\_RESERVED\_27,  
NAL\_UNIT\_RESERVED\_28,  
NAL\_UNIT\_RESERVED\_29,  
NAL\_UNIT\_RESERVED\_30,  
NAL\_UNIT\_RESERVED\_31,  
  
NAL\_UNIT\_VPS, // 32  
NAL\_UNIT\_SPS, // 33  
NAL\_UNIT\_PPS, // 34  
NAL\_UNIT\_ACCESS\_UNIT\_DELIMITER, // 35  
NAL\_UNIT\_EOS, // 36  
NAL\_UNIT\_EOB, // 37  
NAL\_UNIT\_FILLER\_DATA, // 38  
NAL\_UNIT\_SEI, // 39 Prefix SEI  
NAL\_UNIT\_SEI\_SUFFIX, // 40 Suffix SEI  
NAL\_UNIT\_RESERVED\_41,  
NAL\_UNIT\_RESERVED\_42,  
NAL\_UNIT\_RESERVED\_43,  
NAL\_UNIT\_RESERVED\_44,  
NAL\_UNIT\_RESERVED\_45,  
NAL\_UNIT\_RESERVED\_46,  
NAL\_UNIT\_RESERVED\_47,  
NAL\_UNIT\_UNSPECIFIED\_48,  
NAL\_UNIT\_UNSPECIFIED\_49,  
NAL\_UNIT\_UNSPECIFIED\_50,  
NAL\_UNIT\_UNSPECIFIED\_51,  
NAL\_UNIT\_UNSPECIFIED\_52,  
NAL\_UNIT\_UNSPECIFIED\_53,  
NAL\_UNIT\_UNSPECIFIED\_54,  
NAL\_UNIT\_UNSPECIFIED\_55,  
NAL\_UNIT\_UNSPECIFIED\_56,  
NAL\_UNIT\_UNSPECIFIED\_57,  
NAL\_UNIT\_UNSPECIFIED\_58,  
NAL\_UNIT\_UNSPECIFIED\_59,  
NAL\_UNIT\_UNSPECIFIED\_60,  
NAL\_UNIT\_UNSPECIFIED\_61,  
NAL\_UNIT\_UNSPECIFIED\_62,  
NAL\_UNIT\_UNSPECIFIED\_63,  
NAL\_UNIT\_INVALID,  
\};

二， SPS解析

1、重新定义类型

typedef unsigned char uint8;

typedef unsigned short uint16;

typedef unsigned longuint32;  
typedef unsigned \_\_int64uint64;  
typedef signed charint8;  
typedef signed shortint16;  
typedef signed longint32;  
typedef signed \_\_int64int64;

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;  
\}

4、测试代码

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;  
\}

音视频开发训练营公众号  
  
\---------------------  
作者：lcyw  
来源：CSDN  
原文：https://blog.csdn.net/machh/article/details/72190321  
版权声明：本文为博主原创文章，转载请附上博文链接！

[https_blog.csdn.net_machh_article_details_72190321]: https://blog.csdn.net/machh/article/details/72190321