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Image and Video Compression

Image and Video Compression. Communication Systems EECE 453 Hassan Mansour. Image Compression. Most popular techniques: Color subsampling Transform Coding (JPEG, JPEG2000,…) Fractal Coding Available Compression standards: JPEG, JPEG2000, JPEG-LS, JBIG, JBIG2 (ISO)

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Image and Video Compression

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  1. Image and Video Compression Communication Systems EECE 453 Hassan Mansour

  2. Image Compression • Most popular techniques: • Color subsampling • Transform Coding (JPEG, JPEG2000,…) • Fractal Coding • Available Compression standards: • JPEG, JPEG2000, JPEG-LS, JBIG, JBIG2 (ISO) • GIF, PNG, TIFF, BMP, WMP,…

  3. JPEG compression DCT(x-128) Zig-Zag Scan Quantization Entropy Coding JPEG file

  4. JPEG quality per compression ratio Original Compressed to 12% Compressed to 2% Compressed to 6%

  5. Video Compression (MPEG) • Started with MPEG-1/H.261 (1991, video CD) • MPEG-2 was launched in 1994 and became the standard for DVDs. • Finally, MPEG-4 was introduced in 1998. • MPEG-4 ISO is based on H.263 • MPEG-4/AVC is the new H.264 standard used in HD-DVD and Blu-ray Disc. • Both MPEG-4 ISO and H.264/AVC are used for mobile video.

  6. Basic Compression Algorithm Picture N Picture N+1 Difference • Encode picture N as JPEG • Perform Motion Estimation/Compensation on picture N+1 using picture N • Encode the difference as JPEG Motion Estimation / Compensation :

  7. Decoding example Residual Signal Motion- Compensated + Decoded Signal

  8. Video Compression Reference • http://mia.ece.uic.edu/~papers/WWW/MultimediaStandards/chapter7.pdf

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