Digital Video

1
Digital Video

• Considerations
• Quantizatioin, PCM, Resolution, Bit Stream
• Why is a digital video system more demanding than
  audio?
• a.) Bandwidth
• b.) Frames at 30 fps.
• c.) Time duration of video. (ex. 2 hour movie)

2
Digital Video

• Remedies
• a.) Word size
• b.) Compression techniques
• c.) Processor speed and memory improvements

3
Digital Video

• Still Frame versus Real Motion.
• Still Frame
• a.) Why need for compression?
• b.) Types used? i.) Jpeg ii.) GIF etc.
• Does a still frame contain spatial or temporal
  information? _____________

4
Digital Video

• Compression Techniques
• a.) JPEG
• b.) MPEG

5
Digital Video

• Hardware mechanisms
• a.) DSP digital signal processing
• b.) video processing engines (chip sets with
  algorithms)

6
Digital Video

• Real image benchmark of 46 dB
• Requires 33 levels of quantization.
• Implements 32 levels for 5 bit word.
• Artifacts possible at 5 bits.

7
Digital Video

• Compression techniques implemented to reduce
  data
• a.) truncation, clut, run length (simple)
• b.) DPCM differential pulse code
  modulation(predictive)
• c.) ADPCM (predictive)
• d.) Fourier (transform)
• e.) DCT discrete cosine transform
  
• f.) Huffman (statistical)
• Note b,c,d, and e identify redundancies in
  image.

8
Digital Video

• Full Motion video 30fps
• Motion compensation A pixel by pixel compare
  between frames or blocks identifies redundancies.
  Almost always some change in pixels.Motion
  artifacts may develop.
• Remedy Set limit where a small change in pixwls
  is the same as no change.

9
Digital Video

• COMPRESSION TECHNIQUES
• JPEG Key and Delta frames
• MPEGI (intra) frame
• P (predictive) frame
• B (bidirectional) frame