T.Sharon-A.Frank 1 Multimedia Size of Data Frame

2 T.Sharon-A.Frank Major Issues 1. Size of Data Frame 2. Need High Bandwidth 3. Digital vs. Analog Representation 4. Multi-Modality Integration/Blending 5. Soft Real-Time Constraints 6. Need Group Communication 7. Need Synchronization 8. Need for Standards

3 T.Sharon-A.Frank 1. Size of Data Frame

4 T.Sharon-A.Frank Storage Requirements 580 MB 1 GB 1 GB 500 MB 100 MB 100 MB 6.4 MB 10 MB 1 MB 1 MB 500 pages 100 fax line 100 color 10 min of 10 min of 1 hour of of text images images animation video video (uncompr.) (compr. 15:1) ( compr. 15:1) (compr. 30:1) ( compr. 200:1)

5 T.Sharon-A.Frank Use Compression Use Smaller Frame Size Solutions

6 T.Sharon-A.Frank (Smaller) Frame Sizes 640x480352x288174x144 PAL CIF QCIF (Q)CIF – (Quarter) Common Interchange Format

7 T.Sharon-A.Frank What is Compression? Process of reducing the amount of data required to represent a given quantity of information. Same amount of information represented using fewer bits – relies on the notion of data redundancy. Sometimes called packing, coding, encoding or zipping.

8 T.Sharon-A.Frank Compression Necessity (1) Network 2. Bus 1. Storage 3. Communications

9 T.Sharon-A.Frank Compression Necessity (2) 1.Storage – data is compressed before being stored, decompressed before being retrieved. 2.Bus – compressed data transfer requires reduced bandwidth. 3.Communications – sender compresses data before sending it over line, receiver decompresses it after receiving it.

10 T.Sharon-A.Frank Compression Characteristics (A)Symmetrical Compression Lossless/Lossy Compression Spatial/Temporal Compression

11 T.Sharon-A.Frank Types of Compression Entropy encoding – lossless. Data considered a simple digital sequence and semantics of data are ignored. Source encoding – lossy. Takes semantics of data into account. Amount of compression depends on data contents. Hybrid encoding – combination of entropy and source. Most multimedia systems use these.

12 T.Sharon-A.Frank Compression Schemes (1) Lossless Compression Method files are packed and unpacked without losing original data. Run Length Encoding (RLE): Algorithm – redundant information replaced with run length code. Symmetrical Lossy Compression Method – some loss of original data. Joint Photographic Expert Group (JPEG): Uses DCT algorithm, works best on images without sharp edges or detail. Spatial Compression – redundancies in images are compressed.

13 T.Sharon-A.Frank Compression Schemes (2) Asymmetrical Lossy Compression – some loss of original data. Motion Picture Expert Group (MPEG): applies predictive inter- frame coding techniques. Combination of Spatial and Temporal compression – checks for redundancies within frame and from frame to frame.

14 T.Sharon-A.Frank Compression Standards (1) Joint Photographic Experts Group (ISO) International Standard for Continuous-Tone Still Image Compression (Color Pictures, Slides) Recommended in 1991 JPEG P*64 Multiple of 64 Kbps Coding (CCITT) International Standard for Video Telephony, Conferencing and Collaboration Recommended in Q4 1990

15 T.Sharon-A.Frank Compression Standards (2) Motion Pictures Experts Group (ISO) International Standard for Compression of Addressable Video Recommended in Q MPEG-1 MPEG-2 International Standard for Digital Broadcast Quality TV Recommended in Q International Standard for Narrowband Digital Broadcast of Media Objects Recommended in Q MPEG-4

16 T.Sharon-A.Frank Compression Standards (3) High Definition Television (FCC) Next Generation Standard for High Resolution Broadcast TV Recommended in Q (ATSC DTV) HDTV

17 T.Sharon-A.Frank Video Coding Techniques MPEG1: standard for storage and retrieval of moving pictures and audio (VCR quality) on storage media (CD-ROM, WORM). MPEG2: standard for digital TV quality. MPEG4, H.261: standard for multimedia applications at very low bit-rate. MPEG7: multimedia content representation standard for information search.

18 T.Sharon-A.Frank Emerging Market Segments (1)

19 T.Sharon-A.Frank Emerging Market Segments (2)