Practical Applications for Digital Audio Networking

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There are dozens of networking protocols utilized by today's manufacturers of professional audio and video equipment, most of which are not interoperable. Connecting equipment digitally can be confusing, complicated, and expensive. Bob Vanden Burgt of Link USA discusses the evolution of digital networking in the live audio industry, the transport protocol 'wars', and methods for remote control and monitoring of DSPs. Bob concludes with a 'real world' update on the state of existing protocols, and future directions for AES, the AVnu alliance, and the OCA alliance.

Text of Practical Applications for Digital Audio Networking

  • 1. Practical Applications forDigital Audio Networking IIUmberto Zanghieri - ZP Engineering srl(The Smart Guy who is not here today and would be happy to talkabout this topic for two days)Bob Vanden Burgt - Link USA/Link Italy(The Not So Smart Guy doing the Presentation who promises to bedone inone hour)People and Products connecting the world of entertainment

2. Practical Applications forDigital Audio NetworkingHistory of Digital Audio NetworkingAES & Evolution of OSI LayersThe Current State of the Industry(fragmented at best)Transport Protocol WarsRemote Control & MonitoringConnectivity Challenges &Practical ExamplesWhere are We Going from Here? People and Products connecting the world of entertainment 3. Analog DistributionPeople and Products connecting the world of entertainment 4. Digital DistributionPeople and Products connecting the world of entertainment 5. Analog v. Digital Cabling 48-channel balanced analog multicoreWeight approx. 1,3 kg/m; 97 kg for 100m + 25kg cable drumCost approx. 20 times the cost of a CAT5e ruggedized cableOuter diameter 28 mm vs 2 x CAT6 + 2 x AES (Eurocable)Weight approx. 0,38 kg/mOuter diameter 18 mmPeople and Products connecting the world of entertainment 6. Moving Audio Around Digitally ina Live Production Environment What do we need to care about? Quality (Fidelity) Speed & Priority (Latency - milliseconds/microseconds, QoS) Synchronization (Clocking) Distance (Coax, CAT6, MMF, SMF) Flexibility / Compatibility (Topologies / Sharing Hardware) Cost Reliability / Redundancy Compatibility / Standards AES, IEEEPeople and Products connecting the world of entertainment 7. History of Digital Networking Pulse Code Modulation (PCM) & SamplingIn 1924 while working for AT&THarry Nyquist studied thissampling technique anddeveloped the Nyquist SamplingTheorem. This theorem statesthat an analog signal can beuniquely reconstructed, withouterror, from samples taken atSampling Rate = 2(BW) = 2(3300 equal time intervals if theHz) = 6600 Samples per Second sampling rate is equal to, orgreater than, twice the highestfrequency component in theanalog signal. People and Products connecting the world of entertainment 8. Pro Audio & PCMLinear PCM (uncompressed), typ. Wordlength (bit depth) from 16 to 24 bits with sampling frequencies between 44-192kHzPulse-code modulation (PCM) is a method used to digitally represent sampled analogsignals. It is the standard form for digital audio in computers and various Blu-ray, DVD andCompact Disc formats, as well as other uses such as digital telephone systems. A PCMstream is a digital representation of an analog signal , in which the magnitude of the analogsignal is sampled regularly at uniform intervals, with each sample being quantized to thenearest value within a range of digital steps.PCM streams have two basic properties that determine their fidelity to the original analogsignal: the sampling rate, which is the number of times per second that samples aretaken; and the bit depth, which determines the number of possible digital values that eachsample can take. People and Products connecting the world of entertainment 9. History of DigitalNetworkingPublic Switched Telephone Network(PSTN) Coder-Decoder (CODEC) or ADC / DACPeople and Products connecting the world of entertainment 10. History of Digital Networking Pulse Code ModulationPublic Switched Telephone Network(PSTN)CODECs use a method called Pulse CodeModulation (PCM) toconvert the analog signalsto digital bit streams. PCMuses a technique called sampling to obtain instantaneous voltage values at specific times inthe analog signal cycle. This sample generates aPulse Amplitude Modulated (PAM) signal. People and Products connecting the world of entertainment 11. Audio-over-EthernetLinear PCM (Reference CD is 16 bit resolution, 44.1kHz)People and Products connecting the world of entertainment 12. History of DigitalNetworkingRecording in the 1990sDigital Audio WorkstationsToken Ring Networks formoving audio data (not real time)Evolution of the DSP > Whyshouldnt the transport bedigital?People and Products connecting the world of entertainment 13. History of DigitalNetworkingAES Standards 1985 AES3 AES/EBU(RS422 Derived)2 Channels @ 192kHz 1991 AES10 MADI(FDDI Fibre Disrtib Data Interface)56 > 64 Channels @ 96kHz 2005AES50>SuperMAC/HyperMAC (Midas-KT)24 Ch @ 96kHz/192 Ch @ 96kHzPeople and Products connecting the world of entertainment 14. Audio-over-EthernetWhat is it?Deployment of an Ethernet network to transfer digital audio streams in real-time Linear PCM (uncompressed), typ. Wordlength (bit depth) from 16 to 24 bits withsampling frequencies between 44-192kHzmultichannel, high channel count (~60 channels in each direction)audo channels are generally bundled in clusterslow latency (< 6 ms) but with DSP transport expectations =