1Spring 2005 EECS150 lec12-projectPage 1EECS150 - Digital DesignLecture 12 – Project DescriptionMarch 1, 2005John WawrzynekSpring 2005 EECS150 lec12-projectPage 2Final Project: Streaming-Audio Receiver• Audio streams (music) will be broadcast over the local area network (LAN) in the lab.• Networked attached devices, pick off one audio stream and play it to headphones or speakers.• Display of “out of band content”, song titles, etc., on mini-LCD Display.• Everyone (working in groups of 2) will design, implement, debug, and demo a networked audio receiver.AudioServernetworkAudioReceiverAudioReceiverstreamssong titleartist2Spring 2005 EECS150 lec12-projectPage 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 AreaSpring 2005 EECS150 lec12-projectPage 4Calinx add-on card3Spring 2005 EECS150 lec12-projectPage 5– Basics of networking– Basics of digital audio– Details of Calinx network interface– Details of Calinx audio interface– Details of Calinx character display– How to organize the “system”AudioServernetworkAudioReceiverAudioReceiverstreamssong titleartistWhat do we need to know (besides general digital design) to do this mapping?Project MappingSpring 2005 EECS150 lec12-projectPage 6Digital Audio– Music waveform– A series of numbers is used to represent the waveform, ratherthan a voltage or current, as in analog systems.• Discrete time: regular spacing of sample values in time. Most digital audio system use 44.1KHz (consumer) sample rate or 48KHz (professional) sample rate. – Lower frequency would limit the maximum representable frequency content. (Human hearing max is 20KHz)• Digital: All inputs/outputs and internal values (signals) take on discretevalues (not analog). Most digital audio systems use 16-bit values (64K possible values for any point in waveform). Using much fewer than 16 bits generates noticeable noise from distortion.4Spring 2005 EECS150 lec12-projectPage 7Analog / Digital Conversion• Converters are used to move from/to the analog domain.• ADC & DAC often combined in a single chip called CODEC (coder/decoder).• Other types of CODECs perform other functions (ex: video conversion, audio compression/decompression).Digital SystemDigital SystemprocessingprocessingrecordingrecordingplaybackplaybacksynthesissynthesisAnalog to DigitalConverter (ADC)sound source(microphone)sample clock26, 46, 51, 55, 51, …Digital to AnalogConverter (DAC)26, 46, 51, 55, 51, …sample clockpoweramplifierdecompressiondecompressioncompressioncompressionSpring 2005 EECS150 lec12-projectPage 8Digital Audio Data-rates• Relatively small storage devices has prompted the development and application of many compression algorithms for music and speech:– Typically compression ratios of 10-100– MP3: 32Kbits/sec - 320Kbits/sec (factor of 4x to 44x)– These techniques are lossy; information is lost. However the better ones (MP3 & AAC for example) used techniques based on characteristics of human auditory perception to drop information of little importance.• In our project, uncompressed audio will be used. – Sufficient network bandwidth to support multiple streams of audio.– Much simpler hardware design.• Uncompressed audio is often referred to as PCM (pulse code modulation) . (.wav files in windows)44.1K samples/sec x 2 (stereo) x 16 bits/samples = 1.4 Mbit/sec = 176,400 Bytes/sec1 minute ≈ 10MByte total5Spring 2005 EECS150 lec12-projectPage 9Local 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 (10/100Mbps, 1/10Gbps), 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 usually call these packets.• 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) headerSpring 2005 EECS150 lec12-projectPage 10Ethernet 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. In most applications a frame with an invalid CRC is discarded by the MAC receiver. Ethertypes for EECS150 project: 0x0101: audio packets0x0102: LCD packets(picked from the range of “experimental” type codes to avoid potential conflict.– One way transmission only.– All packets will be broadcasted• 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 common 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).6Spring 2005 EECS150 lec12-projectPage 11Protocol 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.application layerex: httpTCPIPMACLayer 2Layer 3Layer 4Layer 5Streaming Ex. Mpeg4UDPIPMACLayer 2Layer 3Layer 4Layer 5Spring 2005 EECS150 lec12-projectPage 12Digital Audio Packetization• Audio packet (type=0x0101)shown above:– Destination address is always
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