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Android audio and video development, video coding, audio coding format

1. Video coding

(1)MPEG series

(2)H.26X series

2. Audio encoding

(1)AAC

advantage : be relative to MP3 Its sound quality is better , File smaller .

shortcoming : It's a loss of sound quality

(2)MP3

characteristic : The compression ratio can reach 1:10 Even 1:12.

Taking advantage of the fact that the human ear is insensitive to high-frequency sound signals , Convert time domain waveform signal into frequency domain signal , Divide multiple bands , Use high compression rate for high frequency signals , Low frequency signals use a small compression rate , Make sure the signal is not distorted .

(3)AC3

Lossy audio encoding format

Widely used in 5.1 channel ,Dolby AC3 The surround sound system provided by 5 It consists of a full frequency channel and a subwoofer channel , go by the name of 5.1 channel .

5 A full frequency channel : Left front 、 The central 、 Right front 、 Back left 、 Right rear .

The subwoofer channel mainly provides some extra bass information , Make some scenes ( The explosion 、 To hit ) The sound is better .

3. Common multimedia frameworks

(1)VLC: namely Video LAN Client, It's a freedom 、 Open source cross platform multimedia player and framework .

(2)FFmpeg: Multimedia solutions , It's not a multimedia framework , Widely used in audio and video development

(3)Gstreamer: A set of open source multimedia framework for streaming media applications .

4. Color space model

YUV: It is a color coding method adopted by European TV system .

Y For brightness ,UV For color difference ,U and V It's the two components that make up the color

RGB: Through the red (R)、 green (G)、 blue (B)3 Changes in color channels and their superposition with each other to get a variety of colors .

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