Đang tải... (xem toàn văn)
THE NATURE OF THE DESIGN PROBLEM 12.2 INTERFACE DESIGN 12.3 IMPLEMENTATION 12.4 PERFORMANCE 12.5 PROJECT MANAGEMENT 12.6 TRENDS IN OPERATING SYSTEM DESIGN 12.7 SUMMARY
7 MULTIMEDIA OPERATING SYSTEMS 7.1 INTRODUCTION TO MULTIMEDIA 7.2 MULTIMEDIA FILES 7.3 VIDEO COMPRESSION 7.4 MULTIMEDIA PROCESS SCHEDULING 7.5 MULTIMEDIA FILE SYSTEM PARADIGMS 7.6 FILE PLACEMENT 7.7 CACHING 7.8 DISK SCHEDULING FOR MULTIMEDIA 7.9 RESEARCH ON MULTIMEDIA 7.10 SUMMARY Distribution network Distribution network Fiber Video server Video server Copper twisted pair Junction box Junction box House Cable TV coaxial cable Fiber (a) (b) Fig. 7-1. Video on demand using different local distribution tech- nologies. (a) ADSL. (b) Cable TV. Source Mbps GB/hr Telephone (PCM) 0.064 0.03 MP3 music 0.14 0.06 Audio CD 1.4 0.62 MPEG-2 movie (640 × 480) 4 1.76 Digital camcorder (720 × 480) 25 11 Uncompressed TV (640 × 480) 221 97 Uncompressed HDTV (1280 × 720)648 288 Device Mbps Fast Ethernet 100 EIDE disk 133 ATM OC-3 network 156 SCSI UltraWide disk 320 IEEE 1394 (FireWire) 400 Gigabit Ethernet 1000 SCSI Ultra-160 disk 1280 Fig. 7-2. Some data rates for multimedia and high-performance I/O devices. Note that 1 Mbps is 10 6 bits/sec but 1 GB is 2 30 bytes. 1432 5678 Hello, Bob Hello, Alice Nice day Sure is How are you Great And you Good Dag, Bob Dag, Alice Mooie dag Jazeker Hoe gaat het Prima En jij Goed Video English audio French audio German audio English subtitles Dutch subtitles Fast forward Fast backward Frame Fig. 7-3. A movie may consist of several files. 1.00 0.75 0.50 0.25 0 –0.25 –0.50 –0.75 –1.00 1 2 T 1 2 T TTT (a) (b) (c) 1 2 T Fig. 7-4. (a) A sine wave. (b) Sampling the sine wave. (c) Quantiz- ing the samples to 4 bits. Scan line 1 3 5 7 9 11 13 15 483 Time . . . The next field starts here Scan line painted on the screen Horizontal retrace Vertical retrace Fig. 7-5. The scanning pattern used for NTSC video and televi- sion. 480 640 (a) (b) Q RGB YI 640 480 240 320 240 1 Block Block 4799 8-Bit pixel 24-Bit pixel Fig. 7-6. (a) RGB input data. (b) After block preparation. Y/I/Q Amplitude DCT xFx y Fy Fig. 7-7. (a) One block of the Y matrix. (b) The DCT coefficients. 150 92 52 12 4 2 1 0 80 75 38 8 3 2 1 0 40 36 26 6 2 1 0 0 14 10 8 4 0 1 0 0 4 6 7 2 0 0 0 0 2 1 4 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 DCT Coefficients 150 92 26 3 1 0 0 0 80 75 19 2 0 0 0 0 20 18 13 2 0 0 0 0 4 3 2 1 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Quantized coefficients 1 1 2 4 8 16 32 64 1 1 2 4 8 16 32 64 2 2 2 4 8 16 32 64 4 4 4 4 8 16 32 64 8 8 8 8 8 16 32 64 16 16 16 16 16 16 32 64 32 32 32 32 32 32 32 64 64 64 64 64 64 64 64 64 Quantization table Fig. 7-8. Computation of the quantized DCT coefficients. 150 92 26 3 1 0 0 0 80 75 19 2 0 0 0 0 20 18 13 2 0 0 0 0 4 3 2 1 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Fig. 7-9. The order in which the quantized values are transmitted. [...]... D1 D5 (a) 1 A0 A4 B3 B7 C2 C6 D1 D5 2 A1 A5 B0 B4 C3 C7 D2 D6 4 A3 A7 B3 B7 C3 C7 D3 D7 3 A1 A4 B2 B5 C3 C4 D3 D4 4 A3 A7 B0 B6 C1 C5 D0 D7 (b) 3 A2 A6 B1 B5 C0 C4 D3 D7 (c) 3 A2 A6 B2 B6 C2 C6 D2 D6 4 A3 A7 B2 B6 C1 C5 D0 D4 1 A0 A6 B3 B4 C0 C7 D1 D6 2 A2 A5 B1 B7 C2 C6 D2 D5 (d) Fig 7- 22 Four ways of organizing multimedia files over multiple disks (a) No striping (b) Same striping pattern for all files... point at 15 min (c) Play point at 16 min (d) Play point at 22 min (e) Fig 7- 16 (a) Initial situation (b) After a rewind to 12 min (c) After waiting 3 min (d) After starting to refill the buffer (e) Buffer full 120 Frame 1 Video A A Frame 2 A Audio track T T Video A A Frame 3 A T T Video A A A T T Text track Fig 7- 17 Interleaving video, audio, and text in a single contiguous file per movie Frame Index... C1 A2 B2 C2 A3 EDF A1 B1 C1 A2 B2 C2 A3 0 B4 C2 C C1 10 20 30 40 A5 50 60 B3 A4 B3 70 80 90 C3 A4 100 A5 B4 C3 A5 B4 110 120 130 Time (msec) Fig 7- 12 An example of RMS and EDF real-time scheduling 140 A A1 B B1 A2 A3 B2 C C1 A1 B1 EDF A1 B1 0 B3 B4 C2 RMS 10 20 C1 30 C3 Failed B2 A2 B2 A2 40 A5 A4 50 60 A3 70 C2 80 B3 90 A4 100 110 C3 120 A5 130 B4 140 Time (msec) Fig 7- 13 Another example of real-time...Fig 7- 10 Three consecutive video frames Deadline for A1 Starting moment for A1 , B1, C1 Deadline for B1 Deadline for C1 A A1 B A2 A3 B1 B2 C C1 0 A4 B3 20 30 40 50 B4 C3 C2 10 A5 60 70 80 90 100 110 120 130 140 Time (msec) Fig 7- 11 Three periodic processes, each displaying a movie The frame rates and processing requirements per frame are different for each movie A A2 A1 B A3 B1 A4 B2 B3 C3 RMS A1 B1... larger than frame I Disk block smaller than frame I I I Audio Text I I I-frame P-frame Unused I (a) (b) Fig 7- 18 Noncontiguous movie storage (a) Small disk blocks (b) Large disk blocks Order in which blocks are read from disk Stream Stream 24 23 Stream 15 Stream 1 Track 1 0 9000 18000 270 00 36000 45000 54000 63000 72 000 81000 2 070 00 Track 2 1 9001 18001 270 01 36001 45001 54001 63001 72 001 81001 2 070 01... 270 00 36000 45000 0 9000 18000 270 00 36000 0 9000 18000 270 00 0 9000 18000 0 1 9000 9000 2 3 4 Frame 9000 in stream 3 is sent at 8:20 min 5 6 7 8 9 0 8:00 8:05 8:10 8:15 8:20 8:25 8:30 8:35 8:40 8:45 Time Fig 7- 15 Near video on demand has a new stream starting at regular intervals, in this example every 5 minutes (9000 frames) Minutes 0 30 60 Play point at 75 min 90 (a) Play point at 12 min (b) Play... sorted on rank order (New York is 1, Los Angeles is 2, Chicago is 3, etc.) Frequency of use Movie 10 Movie 8 Movie 6 Movie 4 Movie 2 Movie 1 Movie 3 Movie 5 Movie 7 Movie 9 Movie 11 Cylinder Fig 7- 21 The organ-pipe distribution of files on a video server Disk 1 A0 A1 A2 A3 A4 A5 A6 A7 2 B0 B1 B2 B3 B4 B5 B6 B7 3 C0 C1 C2 C3 C4 C5 C6 C7 4 D0 D1 D2 D3 D4 D5 D6 D7 1 A0 A4 B0 B4 C0 C4 D0 D4 2 A1 A5 B1 B5... 72 001 81001 2 070 01 Track 3 2 9002 18002 270 02 36002 45002 54002 63002 72 002 81002 2 070 02 Frame 270 02 (about 15 min into the movie) Fig 7- 19 Optimal frame placement for near video on demand 0.300 Frequency 0.250 0.200 0.150 0.100 0.050 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Rank Fig 7- 20 The curve gives Zipf’s law for N = 20 The squares represent the populations of the 20 largest cities in... streams into one Stream 1 2 3 4 5 6 7 8 9 10 70 1 92 281 130 326 410 160 466 204 524 466 524 70 1 Buffer for odd frames Buffer for even frames Block requested Optimization algorithm 92 130 160 204 281 326 410 Order in which disk requests are processed Fig 7- 24 In one round, each movie asks for one frame Requests (sorted on deadline) Batch together 330 Cylinder 70 0 676 71 0 110 680 440 72 0 220 75 5 280 73 0... all files (c) Staggered striping (d) Random striping 10 sec 0 2 min 3 min 4 min 1 8 0 0 User 1 1 min 3 6 0 0 5 4 0 0 7 2 0 0 User 2 0 Starts 10 sec later 5 4 0 0 3 6 0 0 1 8 0 0 7 2 0 0 Time (a) Runs slower Normal speed 3 6 0 0 1 8 0 0 User 1 0 User 2 0 3 6 0 0 1 8 0 0 Runs faster 5 4 0 0 7 2 0 0 5 4 0 0 7 2 0 0 Normal speed (b) Fig 7- 23 (a) Two users watching the same movie 10 sec out of sync (b) Merging . After waiting 3 min. (d) After starting to refill the buffer. (e) Buffer full. Video A A A T T Video A A A T T Video A A A T T Frame 3Frame 2Frame 1 Audio track Text track Fig. 7-17. Interleaving. (msec) A B C C2 C3C1 Fig. 7-11. Three periodic processes, each displaying a movie. The frame rates and processing requirements per frame are different for each movie. A1 A1 A1 B1 B1 A2 A2 A2 A3 A3 . 5678 Hello, Bob Hello, Alice Nice day Sure is How are you Great And you Good Dag, Bob Dag, Alice Mooie dag Jazeker Hoe gaat het Prima En jij Goed Video English audio French audio German audio English