1 University of Canberra Advanced Communications Topics Television Broadcasting into the Digital Era by: Neil Pickford Lecture 2 Digital Video Formats, Standards and Sampling

2 Standard Definition Television SDTV n The current television display system n 4:3 aspect ratio picture, interlace scan n Australia/Europe u 625 lines pixels x 576 lines displayed u 50 frames/sec 25 pictures/sec u pixels total n USA/Japan u 525 lines pixels x 480 lines displayed u 60 frames/sec 30 pictures/sec u pixels total

3 Enhanced Definition Television EDTV n Intermediate step to HDTV n Doubled scan rate - reduce flicker n Double lines on picture - calculated n Image processing - ghost cancelling n Wider aspect ratio - 16:9 n Multi-channel sound

4 High Definition Television - HDTV n Not exactly defined - number of systems n System with a higher picture resolution n Greater than 1000 lines resolution n Picture with less artefacts or distortions n Bigger picture to give a viewing experience n Wider aspect ratio to use peripheral vision n Progressive instead of interlaced pictures

5 HDTV Have We Heard This Before? n The first TV system had just 32 lines n When the 405 line system was introduced it was called HDTV! n When 625 line black & white came along it was called HDTV! n When the PAL colour system was introduced it was called HDTV by some people. n Now we have line systems and digital television - guess what? Its called HDTV!

6 Do You Use A PC? All Current Generation PCs use Progressive Scan and display Pictures which match or exceed HDTV resolutions although the pixel pitch, aspect ratio and colorimetry are not correct. HDTV

7 Digital Television Why digital? To Overcome Limitations of Analog Television n Noise free pictures n Higher resolution images Widescreen / HDTV n No Ghosting n Multi-channel, Enhanced Sound Services n Other Data services.

8 Enabling Technologies n Source digitisation (Rec 601 digital studio) n Compression technology (MPEG, AC-3) n Data multiplexing (MPEG) n Display technology (large wide screens) n Transmission technology (modulation) n Production

9 Sampling n Digital video requires sampling of the Analog image information. n Highest quality achieved when sampling Component video signals. n For SDTV a basic luminance sampling frequency of 13.5 MHz has been adopted. n Various methods exist to sample the complete colour image information 4:2:24:4:4 4:1:14:2:0

10 YUV Y OnlyYUV 4:4:4 & 4:2:2 Sampling YUV Sampling Points 13.5 MHz 4:2:2 4:4:4

11 YUV Y Only Y Only Y Only 4:1:1 & 4:2:0 MPEG-1 Sampling 4:2:0 YUV Sampling Points 13.5 MHz 4:1:1 Y V Y Y U Y JPEG/JFIF H.261 MPEG-1

12 YUV Y Only Y Only Y Only 4:1:1 & 4:2:0 MPEG-2 Sampling 4:2:0 YUV Sampling Points 13.5 MHz 4:1:1 YV Y Only YU Y Only Co-sited Sampling MPEG-2

13 Rec BT-601/656 n Digital Standard for Component Video n 27 MHz stream of 8 / 10 bit 4:2:2 Samples n 8 bit range 219 levels black to white (16-235) n Sync/Blanking replaced by SAV & EAV signals n Ancilliary data can be sent during Blanking & 255 YVU

14 Parallel BT-656 n 1st Rec 656 connection format used. n Uses 110 Ohm twisted pairs for data and clock n ECL level 27 MHz n Width: 10 bits NRZ data + 1 clock pair n Uses standard DB-25 Female on Equipment n All cables are DB-25 Male to Male pin for pin n All cables have overall shield to prevent EMI n Max length without a DA 50 m, with EQ 200 m

15 SDI - Serial BT-656 n Serial Data Interface - Current version of 656 n Uses standard 75 Ohm video coax Cabling n 1300 nm Optical fibre interface also defined n 270 Mb/s Serial data stream of 10 bit data n X 9 +X 4 +1 scrambling used for data protection n Encoding polarity free NRZI 800 mV pk-pk n 4 channel Audio can be encoded into ancillary data areas during the blanking period

16 Video Formats - SDTV - 50 Hz All these formats are Interlaced

17 Video Formats - HDTV - 50 Hz

18 HD Video Formats ,073, ,658, , , ,600 1,552,200

19 Common Image Format CIF n 1920 pixels x 1080 lines is now being promoted as the world CIF. n All HDTV systems will need to support this image format and then allow conversion to any other display formats that are supported by the equipment. n In Australia we have adopted the CIF for our HDTV production format. The Recommended Video format is 1920 x 1080 Interlaced at 50 Hz with a total line count of 1125 lines.

20 HDTV Parameters - AS 4599 n HDTV Defined as a MPEG-2 stream which is compliant with encoding. n HDTV sample rate: u Less than samples per second u Greater than samples per second n Systems with less than samples per second are defined as SDTV

21 Chromaticity u SDTV needs compatibility with legacy displays, so default SDTV chromaticity in DVB is: F same as PAL for 25Hz F same as NTSC for 30Hz u HDTV has unified world-wide chromaticity and no legacy displays F default is BT.709 for both 25Hz and 30Hz F simulcast allows mixture of legacy chromaticity for SDTV and BT.709 for HDTV

22 BT-709 Colorimetry n HDTV uses a different colour space to SDTV n HDTV display Phosphors not same as SDTV n BT-709 defines the parameter values for HDTV n HDTV has a slightly different colour equation Y = R G B U = (B - Y) V = (R - Y) Colour Difference Signals