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Berkeley COMPSCI 150 - Lecture 15 – Project Description, Part 2

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1Fall 2002 EECS150 lec15-proj2Page 1EECS150 - Digital DesignLecture 15 – Project Description, Part 2October 15, 2002John WawrzynekFall 2002 EECS150 lec15-proj2Page 2eTV (ethernet TV)Audio/VideoBroadcastServernetworkEthernetTVReceiverEthernetTVReceiverAudio/video streams• Multiple audio/video streams are broadcast over the 100Mbit switched Ethernet in the lab.• Each stream is one broadcast “channel”.• No audio requirement this semester.• The receiver must selects a particular channel from the network and displays the video on the monitor and the play the audio out the headphone jack. • Everyone (working in groups of 2) will design, implement, debug, and demo a receiver for Ethernet TV using the Calinxboard.Fall 2002 EECS150 lec15-proj2Page 3Outline1. Rough calculations / feasibility 2. Network Side–LANs– Network stacks– Ethernet–RTP– 125 Network Architecture– Calinx Network Interface 3. Video Side–Basics– CIF standard– ITU-R 601 video standard– Calinx Codec Interface– Transcoding Options4. eTV Receiver High-Level Organization5. Calinx DRAM Interface6. Frame buffer design& Sender/Receiver clock drift issues7. Schedule and Design CheckpointsFall 2002 EECS150 lec15-proj2Page 4Calinx BoardFlash Card & Micro-drive PortVideo Encoder & DecoderAC ’97 Codec & Power AmpVideo & Audio PortsFour 100 Mb Ethernet Ports8 Meg x 32SDRAMQuad Ethernet TransceiverXilinxVirtex 2000ESeven Segment LED DisplaysPrototype Area2Fall 2002 EECS150 lec15-proj2Page 5eTV Receiver High-level OrganizationPHYEtherportsMACReceiverpacketfilter/parserreceive bufferSDRAMVideoEncoders-videoFrame BufferControlFrame BuffersFPGA25MHz 27MHzFall 2002 EECS150 lec15-proj2Page 6Digital Video Basics• Pixel Array:– A digital image is represented by a matrix of values where each value is a function of the information surrounding the corresponding point in the image. A single element in an image matrix is a picture element, or pixel. A pixel includes info for all color components.– The array size varies for different applications and costs. Some common sizes shown to the right.• Frames: – The illusion of motion is createdby successively flashing still pictures called frames.19201080High-Definition Television (HDTV), 2 Mpx1152900Workstation, 1 Mpx800600PC/Mac,1‡2 Mpx640480Video, 300 Kpx352240SIF,82 Kp xHigh-Definition Television (HDTV), 1 Mpx1280720Fall 2002 EECS150 lec15-proj2Page 7Refresh Rates & Scaning• The human perceptual system can be fooled into seeing continuous motion by flashing frames at a rate of around 20 frames/sec or higher. – Much lower and the movement looks jerky and flickers. TV in the US uses 30 frames/second (originally derived from the 60Hz line current frequency). • Images are generated on the screen of the display device by “drawing” or scanning each line of the image one after another, usually from top to bottom. • Early display devices (CRTs) required time to get from the end of a scan line to the beginning of the next. Therefore each line of video consists of an active video portion and a horizontal blanking intervalportion.• A vertical blanking interval corresponds to the time to return from the bottom to the top. – In addition to the active (visible) lines of video, each frame includes a number of non-visible lines in the vertical blanking interval. – The vertical blanking interval is used these days to send additional information such as closed captions and stock reports.Fall 2002 EECS150 lec15-proj2Page 8Interlaced Scanning• Early inventers of TV discovered that they could reduce the flicker effect by increasing the flash-rate without increasing the frame-rate.• Interlaced scanning forms a complete picture, the frame, from two fields, each comprising half the scan lines. The second field is delayed half the frame time from the first.• Non-interlaced displays are call progressive scan.• The first field, odd field, displays the odd scan lines, the second, even field, displays the even scan lines.3Fall 2002 EECS150 lec15-proj2Page 9Pixel Components• A natural way to represent the information at each pixel is with the brightness of each of the primary color components: red, green and blue (RBG).– In the digital domain we could transmit one number for each of red, green, and blue intensity.• Engineers had to deal with issue when transitioning from black and white TV to color. The signal for black and white TV contains the overall pixel brightness (a combination of all color components).– Rather than adding three new signals for color TV, they decided to encode the color information in two extra signals to be used in conjunction with the B/W signal for color receivers and could be ignored for the older B/W sets.• The color signals (components) are color differences, defined as:B-Y and R-Y, where Y is the brightness signal (component).• In the digital domain the three components are called:Y luma, overall brightnessCBchroma, Y-BCRchroma,Y-R• Note that it is possible to reconstruct the RGB representation if needed.• One reason this representation survives today is that the human visual perceptual system is less sensitive to spatial information in chrominance than it is in luminance. Therefore chroma components are usually subsampled with respect to luma component.Fall 2002 EECS150 lec15-proj2Page 10Chroma SubsamplingR0R2R1R3G0G2G1G3B0B2B1B3Y0Y2Y1Y3CBCBCBCBCRCRCRCRY0Y2Y1Y3CB 0-1CB 2-3CR 0-1CR 0-1Y0Y2Y1Y3CB 0-3CR 0-3Y0Y2Y1Y3CB 0-3CR 0-3RGB 4:4:4 Y CR CB 4:4:4 4:2:2 (ITU-601) 4:2:0 (MPEG-1) 4:2:0 (MPEG-2)• Variations include subsampling horizontally, both vertically and horizontally.• Chroma samples are coincident with alternate luma samples or are sited halfway between alternate luna samples. Fall 2002 EECS150 lec15-proj2Page 11Common Interchange Format (CIF)• Common Interchange Format (CIF)• Developed for low to medium quality applications. Teleconferencing, etc.• Variations: – QCIF, 4CIF, 16CIF• eTV uses CIF, withcomponent streaming as:line i: Y CR Y Y CR Y Y…line i+1: Y CB Y Y CB Y Y…Alternate (different packet types):line i: Y CR Y CB Y CR Y CB Y …line i+1: Y Y Y Y Y …Bits/pixel: – 6 components / 4 pixels– 48/4 = 12 bits/pixelThe Berkeley MPEG-1 Decoder outputs this format. Our video server will broadcast video in this format.interstitialChroma alignment12Effective bits/pixel8Bits per component4:2:02:1 in both X & YChroma


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Berkeley COMPSCI 150 - Lecture 15 – Project Description, Part 2

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