Audio and video learning (II) -- frame rate, code stream and resolution

Frame rate （FPS）

The frame rate is the number of images displayed per second . Each frame is a still image , The fast and continuous display of multiple frames forms a moving " illusion ".

The more frames per second ,FPS The higher the value , The smoother the video action displayed , The greater the bitstream demand .

stream （Bit Rate）

The data flow of video data in unit time , Also called bit rate , It is the most important part of video coding picture quality control . At the same resolution and frame rate , The larger the code stream of video data , The smaller the compression ratio , The higher the picture quality .

The resolution of the （Resolution）

The size or size of an image .

Common resolutions are 4CIF(704*576)、CIF(352*288)、QCIF(176*144)、VGA(640*480) And megapixels (1920*1080). In the two sets of imaging numbers , The former is picture length , The latter is the picture width , Multiply the two to get the number of pixels in the picture , The aspect ratio is generally 4:3, In high-definition video monitoring, it mainly includes 16:9.

Video coding technology

• MJPEG Compress
• MPEG-1 —— Digital TV standards ,1992 Official release .
• MPEG-2 —— Digital TV standards ,1994 It became the international standard draft in .
• MPEG-4 —— Multimedia application standards (1999 Released in ).

Video decoding

Video decoding is the reverse process of video coding , Mainly completed by video decoder .

Video decoding is divided into hard decoding and soft decoding . Hard decoding is performed by DSP complete , Soft decoding by CPU complete , The hard decoded output is usually displayed on the TV wall , Soft decoding is directly displayed by computer workstation .