Video codec: The first chapter of the basic coding and decoding

1. Video Coding Concepts

Video encoding refers to the way in which a video format file is converted to another video format file by a specific compression technique .

2. Why video compression?

• Data is too large: uncompressed digital video data volume is huge
• Storage Difficulty: A DVD can store only a few seconds of uncompressed digital video ( standard DVD disc is 4.7GB, double-layer DVD is also 8.5GB)
• Transmission difficulty: 1M of bandwidth transmission of one second array TV video takes about 4 minutes

The amount of video data in a minute

Frame rate (framerate)	Frame Size	Bits/pixel	Bit-rate (bps	File Size (Bytes
30 Frames/sec	176X 144 Pixels	12	9123480 Approx. 1M	68428800 1m*60

3. Compression principle

Removing redundant information

• Spatial redundancy: a strong correlation between image neighboring pixels
• Time redundancy: Similar content between neighboring images of a video sequence
• Coding redundancy: Different pixel values occur in different probabilities
• Visual redundancy: The human visual system is insensitive to certain details
• Knowledge Redundancy: The structure of regularity can be obtained by a priori knowledge of Beijing knowledge

4. Data compression classification

Lossless compression (Lossless)

• The image is exactly the same after decompression
• Low compression ratio (2:1~3:1)
• such as: WINZIP,JPEG-LG

lossy compression (Lossy)

• Image inconsistency after decompression before compression
• Compression ratio (10:1~20:1)
• The use of human visual system characteristics
• such as: Mpeg-2,hello64/avc,avs

5. Codecs

Encoder (Encoder): A device or program that compresses a signal

Decoder (Decoder): Device or program for extracting signals

Codec Go (CODEC): Codec pair

6. Codec System composition

(1) Key technologies in the encoder

(2) Key technologies in coding and decoding

7. Codec implementation

Realization Platform of Codec

• VLSI ASIC,FPGA for large scale VLSI
• DSP for digital signal processor
• Software

Codec products

• Stb
• Digital TV
• Camera
• Monitoring device

8. Video Coding Standard

Coding Standard Effect:

• Compatible: Encoder-coded streams produced by different manufacturers can be decoded by codecs from different manufacturers
• Efficient: Standard codecs are available for mass production and cost savings
• The mainstream video coding standard:

MPEG-2

MPEG-4 Simple Profile

H.264/avc

Avs

VC-1

9. Video transmission

Video transmission: The compressed video stream is transmitted from the encoded end to the decoding end via the transmission system

Transmission system: Internet, terrestrial wireless satellite, satellite

10. Video transmission is facing problems

• The transmission system is unreliable

Bandwidth limit

Signal attenuation

Noise interference

Transmission delay

• Problems with video transmission

Unable to decode the correct video

Video playback delay

11. Video Transmission Error control

• Error control resolves problems caused by data loss or delay during video transmission
• Error control Technology:

Error control technology of channel coding

Encoder Error Recovery

Decoder Error Concealment

12. Oos Parameters for video transmission

• End-to-end delay of a packet
• Bandwidth: bits per second
• Fluctuations in the delay time of the packet

Video codec: The first chapter of the basic coding and decoding