1. SE-3910 Real-time Systems Week 7, Class 3 – Announcement – Estimating rates Uncompressed Video Size Compression Ratio Frame rate – the Stroboscope effect (Aliasing) Channel capacity – Fourier Transform Sampling error SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling, Some from Dr. Hornick, etc. 1

2. How is an image stored in memory? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 2

3. Full HD/1080p SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 3

4. How large is an uncompressed image? 1080p – 1920 x 1080 – 3 channels (RGB), each 8 bits How many bytes for one image? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 4

5. What is the uncompressed data-rate? 1080p – 1920 x 1080 – 3 channels (RGB), each 8 bits – 60 fps What is the data rate, in Xbits per second? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 5

6. H.262 Compression H.262 compression has a target maximum data rate of 25 Mb/s. Supposing this means Mebibits/s (or Megabits/s), what is the desire compression ratio? compression ratio = compressed / uncompressed SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 6

7. The Stroboscopic Effect Have you ever noticed something that is in motion seem to stop? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 7

8. The Stroboscopic Effect (Aliasing) http://upload.wikimedia.org/wikipedia/comm ons/7/77/Propeller_strobe.ogv http://upload.wikimedia.org/wikipedia/comm ons/7/77/Propeller_strobe.ogv http://upload.wikimedia.org/wikipedia/comm ons/e/ef/The_wagon-wheel_effect.ogv http://upload.wikimedia.org/wikipedia/comm ons/e/ef/The_wagon-wheel_effect.ogv SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 8

9. Safety See, e.g. http://www.seasshops.ucla.edu/services/stud ent-faculty-shop/machine-shop-rules http://www.seasshops.ucla.edu/services/stud ent-faculty-shop/machine-shop-rules SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 9

10. Aliasing http://photo.stackexchange.com/questions/2 4512/what-is-aliasing-and-anti-aliasing SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 10

11. More aliasing Single-Sensor Imaging: Methods and Applications for Digital Cameras, by Rastislav Lukac http://www.openphotographyforums.com/for ums/showthread.php?t=14988 SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 11

12. Transmitting data Physical Layer – You didn’t talk too much about this in Network Protocols – Can occur through many mediums Twisted Pair Coaxial Cable Fiber Optics Wireless SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 12

13. Claude Shannon SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 13

14. Signals as sums of sine-waves SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 14 http://mathworld.wolfram.com/FourierSerie sSquareWave.html http://ccn.ucla.edu/BMCweb/SharedCode/s lides/SlideFiles.html

15. What is analog bandwidth? Time Freq. SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 15 http://www.mathworks.com/matlabcentral/fileexchange/22214-voice-audio- processing

16. SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 16

17. Channel capacity SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 17

18. In-class exercise The old analog TV channels had a bandwidth of 6MHz Supposing a SNR of 50 dB, what is the maximum possible bit-rate? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 18

19. Rates SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 19 Wiring TypeBandwidth CAT 316MHz CAT 5100 MHz Coaxial Cable (50 Ohm)1-2 GHz Fiber Optic50000 GHz

20. In-Class Exercise: If this is 1 second, what is the output if we sample 3 times per second? SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 20

21. Sampling Theorem (again Nyquist) f s = 2B (B is bandwidth of signal) SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 21

22. Discretization Consider an analog signal that will vary between two values – say 0 and V H volts Discretization refers to the “levels” the ADC is able to resolve the analog signal to: – a 2-bit converter can resolve 4 different discrete levels SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 22

23. Discretization Error Difference between the actual analog value and quantized digital value due is called quantization error. – Due either to rounding or truncation. SE-3910 - Dr. Josiah Yoder Slide style: Dr. Hornick Much Material: Dr. Schilling 23