Image and Video Compression Communication Systems EECE 453 Hassan Mansour

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

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

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

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

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

Decoding example + Residual Signal Motion- Compensated Decoded Signal

Video Compression Reference timediaStandards/chapter7.pdf timediaStandards/chapter7.pdf