Article catalog
1 Preparation 1.1 H265 Video Document 1.2 Reference Document 1.3 Reference Blog
2 analysis 2.1 nalu type2.1.1 h2642.1.2 h265
2.2 instance analysis
Recently, I learned about the H265 code stream structure. Compared with the H264's code stream structure, some analyzes are made, simply record it, and make an output for the input content, prevent forgetting
1 Preparation
1.1 H265 video file
The H265 video file will be analyzed later, so download the H265 video file provided in the Live555 official website: http://www.live555.com/livemedia/public/265/
1.2 Reference documentation
H264 Code Flow Structure Document Direct Reference Note: "H.264 PC Decoding Software Development Guide.pdf"
H265 Code Flow Structure Document Reference: "T-REC-H.265-201504-I !! PDF-E.PDF"
1.3 reference blog
H265 NALU type judgment and SPS data analysis https://blog.csdn.net/machh/article/details/72190321
HEVC code stream analysis https://blog.csdn.net/crystalshaw/Article/details/80624804
H.265 / hevc learning notes II: Code stream analysis https://blog.csdn.net/c250456789/Article/details/62427968
2 analysis
About SPS / PPS / IDR / P / B, etc., this is no longer detailed. Each NALU prefix code of H264 and H265 is also the same, ie "0x00 00 00 01" or "0x00 00 01".
H265 is more than H264, more concepts, such as VPS, currently in understanding this parameter, detailed understanding of the blog post: HEVC coding structure: sequence parameter set SPS, image parameter set PPS, video parameter set VPS https: / /BLOG.CSDN.NET/LIN453701006/Article/details/52797104
2.1 NALU TYPE
2.1.1 H264
In H264, the first byte followed by each prefix is the syntax element of NALU, mainly three parts: forbidden_bit (1bit), nal_reference_bit (2bits) (priority), NAL_Unit_type (5bits) (Type)
So, in H264, if we need to get the type of NALU, you can analyze the following way:
NALU_TYPE = first_BYTE_IN_NAL & 0x1F
1
NALU_TYPE as follows:
2.1.2 H265
In H265, each preamble is followed by the first two bytes of NALU's syntax elements, mainly four parts:
Forbidden_Zero_bit (1): nal_unit_type (6): nuh_layer_id (6): nuh_temporal_id_plus1 (3)
1
The document is defined as follows: It can be seen that NALU's syntax elements are changed from one byte of H264 to two bytes, and nal_unit_type is NALU type, so we can get the type of NALU by following:
INT TYPE = (Code & 0x7e) >>1;
1
The definition value of TYPE is as follows: The above picture, the Type of the NALU of H265, here you can simply understand the above Type as the type we need: VPS = 32 SPS = 33 PPS = 34 IDR = 19 p = 1 b = 0
2.2 instance analysis
As described below, the head information for the downloaded video file Surfing.265 has seen four NALU packs, and each NALU's header information is:
1 00 00 00 01 40 01 ---. 1882. (0x40 & 0x7e) >>1 = 32 ---. 1882. VPS
2 00 00 01 42 01 ---. 1882. (0x42 & 0x7e) >>1 = 33 ---. 1882. SPS
3 00 00 00 01 44 01 ---. 1882. (0x44 & 0x7e) >>1 = 34 ---. 1882.PS
4 00 00 00 01 26 01 ---. 1882. (0x26 & 0x7e) >>1 = 19 ---. 1882.Idr
1234
It can also be seen from the above head structure, and the NALU is typically 0, and the nuh_layer_id is usually 0, and Nuh_Temport_ID_PLUS1 is usually 1.
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