es码流结构
在其他参考文献中 宏块是最小的单位 不能再被分割 个人比较认同这种说法 故认为es码流应为5层结构
个人理解在H.264中:
SPS信息用于描述图像序列层的信息.
PPS信息用于描述图像的信息.
图像序列 & SPS
通过SPS可获取序列的信息, 比如:
可获取H264的Profile和Level等信息.
解码器获取Profile和Level信息后, 可明白需要准备那些内容来进行解码.获取序列中图像的宽和高.
可通过pic_width_in_mbs_minus1和pic_height_in_map_units_minus1来计算图像的宽和高.获取序列中图像的帧率.
如果包含vui信息, 还可计算出图像的帧率.
GOP
In video coding, a group of pictures, or GOP structure, specifies the order in which intra- and inter-frames are arranged.
The GOP is a group of successive pictures within a coded video stream.
Each coded video stream consists of successive GOPs.
From the pictures contained in it, the visible frames are generated.
Encountering(遇到) a new GOP in a compressed video stream ensures the decoder that no previous frame will be needed to decode the next ones, and is what allows fast seeking through the video.
GOP由一组连续的视频编码图像.
每个视频流有很多连续的GOP组成.
- GOP Structure
The GOP structure is often referred by two numbers, for example, M=3, N=12. The first number tells the distance between two anchor frames (I or P).
The second one tells the distance between two full images (I-frames): it is the GOP size.[2]
For the example M=3, N=12, the GOP structure is IBBPBBPBBPBBI. Instead of the M parameter the maximal count of B-frames between two consecutive anchor frames can be used.
For example, in a sequence with pattern IBBBBPBBBBPBBBBI, the GOP size is equal to 15 (length between two I frames) and distance between two anchor frames (M value) is 5 (length between I and P frames or length between two consecutive P Frames).
GOP的size指的是两个相邻I帧的距离.
Slice & MB
Slices
- 一幅图像被分割成1个或多个片.
- 每个片有很多宏块组成.
Macroblocks
- 基本的处理单元.
- 每个宏块包括一个16*16的亮度采样和两个8*8的色度采样.
- 宏块不能再被分割.
Reference:
新一代视频压缩编码标准 ——H.264/AVC 毕厚杰主编
https://en.wikipedia.org/wiki/Group_of_pictures
https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC
http://iphome.hhi.de/wiegand/assets/pdfs/DIC_H264_07.pdf
