1Fall 2002 EECS150 lec14-proj1Page 1EECS150 - Digital DesignLecture 14 – Project Description Part 1October 10, 2002John WawrzynekFall 2002 EECS150 lec14-proj1Page 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 lec14-proj1Page 3Calinx 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 AreaFall 2002 EECS150 lec14-proj1Page 4Outline1. 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 Checkpoints2Fall 2002 EECS150 lec14-proj1Page 5“Back of the Envelope” Calculations• Normally Digital Video is compressed for transmission over networks:– Common standard is MPEG-2, designed for digital broadcast television level– 720x480 pixels per frame and 30 frames/sec.– Compressed bandwidth is ≤ 15 Mb/s• For simplicity with eTV we will send uncompressed video. – One scan line per network packet.– Video resolution / frame-rate corresponding to decoded MPEG-1– Common Interchange Format (CIF): • 352 pixels per line, 288 lines• 12 bits/pixel• 30 frames/sec• Packet size calculation:352 • 12 ÷ 8 = 528 Bytes/packet– Maximum network packet payload is 1500 Bytes.• “Payload” Bandwidth Calculation:352 • 288 • 30 • 12 = 36.5 Mbits/sec • Calinx board has 4 100 Mbit network interfaces.• Packetization will add communication bandwidth overhead (~10%).• Server can send up to two channels per subnet.• Receiver will pick off one channel for display (more than one for extra credit – multiple displays on one monitor.Fall 2002 EECS150 lec14-proj1Page 6Ethernet Frame CalculationsInterFrame Gap (96 bit times) 12 BytesMAC Preamble (+SFD) 8 BytesMAC Destination Address 6 BytesMac Source Address 6 BytesMAX Type (or Length) 2 BytesPayload (Network PDU) 528 + 12 (RTP headers) = 540 BytesCheck Sequence (CRC) 4 BytesTotal Physical Size 578 BytesMaximum packet rate:Ethernet Data Rate / Total Packet Physical Size100 Mb/s ÷ 578 Bytes = 21,626 packets/secLink layer throughput:packet rate • size of packet payload = 21,626 • (528 • 8) = 91,349,481 b/sFall 2002 EECS150 lec14-proj1Page 7Local Area Network (LAN) Basics• A LAN is made up physically of a set of switches, wires, and hosts. Routers and gateways provide connectivity out to other LANs and to the internet.• Ethernet defines a set of standards for data-rate (10/100/1000 Mbps), and signaling to allow switches and computers to communicate. • Most Ethernet implementations these days are “switched” (point to point connections between switches and hosts, no contention or collisions).• Information travels in variable sized blocks, called Ethernet Frames, each frame includes preamble, header (control) information, data, and error checking. We will call them packetsto avoid confusion with video frames.• Preamble is a fixed pattern used by receivers to synchronize their clocks to the data.• Link level protocol on Ethernet is called the Medium Access Control (MAC) protocol. It defines the format of the packets.switchswitchhosthosthost hostswitchhostto router or gatewayPreamble MAC Payload CRC(8 bytes) headerFall 2002 EECS150 lec14-proj1Page 8Ethernet Medium Access Control (MAC)• MAC protocol encapsulates a payload by adding a 14 byte header before the data and a 4-byte cyclic redundancy check (CRC) after the data.• The CRC provides error detection in the case where line errors result in corruption of the MAC frame. Any frame with an invalid CRC should discarded by the MAC receiver without further processing. Ethertypes for EECS150 eTV: 0x0107(picked from the range of “experimental” type codes to avoid potential conflict.For eTV:– One way transmission only.– Broadcast only: destination address: all 1’s.• A 6-byte destination address, specifies either a single recipient node (unicastmode), a group of recipient nodes (multicast mode), or the set of all recipient nodes (broadcast mode). • A 6-byte source address, is set to the sender’s globally unique node address. Its main function is to allow address learning which may be used to configure the filter tables in switches. • A 2-byte type field, identifies the type of protocol being carried (e.g. 0x0800 for IP protocol).3Fall 2002 EECS150 lec14-proj1Page 9Protocol Stacks• Usual case is that MAC protocol encapsulates IP (internet protocol) which in turn encapsulates TCP (transport control protocol) with in turn encapsulates the application layer. Each layer adds its own headers.• Other protocols exist for other network services (ex: printers).• When the reliability features (retransmission) of TCP are not needed, UDP/IP is used. Gaming and other applications where reliability is provided at the application layer.• RTP: a transport level protocol for real-time applications. – Used for streaming audio and video (for instance webcasting of lectures, etc.).application layerex: httpTCPIPMACStreaming Media App DataRTPUDPIPMACEECS150eTV dataRTPMACUsually it is encapsulated by UDP/IPMay be encapsulated directly in Ethernet MACFall 2002 EECS150 lec14-proj1Page 10RTP: A Protocol for Real-Time Applications• version (V): 210• padding (P), extension (X), and CSRC count (CC): all 0• marker (M):1 for the packet with the first line of a video frame.• payload type (PT):11101112=11910for EECS150 eTV• sequence number:increments by 1 for each packet (scan line)• timestamp:low 10 bits count scan lines, higher bits count frames: • SSRC:eTV channel number0 1 2
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