Audio and video coding knowledge

• Data Compression Performance Metrics
  • Compression ratio:
    • The bigger the better
  • compression quality
    • lossless compression
    • lossy compression
    • subjective rating
    • objective scale
      • mean squared error
      • Peak Signal to Noise Ratio
  • Compression speed and decompression speed
    • most 15
    • Full dynamic 25-30
    • For video transmission over telephone lines, due to the limitation of line transmission, the frame rate requirement is not so high, but it is also required to reach more than 5 frames per second
• Type of data redundancy
  • Spatial redundancy
  • time redundancy
  • Information entropy redundancy
  • visual redundancy
    • Human resolving power is 26 gray levels
  • auditory redundancy
    • 20Hz - 20KHz
  • other redundancy
    • Structural redundancy...
• Data Compression Classification
  • Classify according to whether the decoded data is consistent with the original data:
    • there is a real code
    • Distortionless encoding
  • Classification according to coding principle
    • predictive coding
    • transform coding
    • Statistical encoding ----- Distortion-free encoding
      • run-length encoding
        • Detect repeated sequences of bits or characters
      • LZW encoding
      • huffman coding
    • Analysis - Synthetic Encoding
    • Hybrid encoding
    • some other encoding