www.tandbergtv.com 4 Introduction We will discuss ASI versus IP for digital video connectivity. For IP, we will really concentrate on Gigabit Ethernet. We will discuss: –Physical layer implementation –Timing features –Packet loss issues –Routing of traffic And we will conclude that IP is a good replacement for ASI!
www.tandbergtv.com 5 ASI Versus Gigabit Ethernet Physical ParameterASIGigabit Ethernet Line Bit Rate270 Mb/s1.25 Gb/s Line Coding8B/10B (based on Fiber Channel) Information Bit Rate 216 Mb/s1.0 Gb/s Link TypeUnidirectional point-to-point Dual-Unidirectional point-to-point When to transmit?Whenever I want Byte Synchronization Sends sync pattern when idle Silence when idle, 8-byte sync before packet Frame checkNone (Reed- Solomon optional) CRC
www.tandbergtv.com 6 Physical Layer Notes Gigabit Ethernet is always switched –No contention –Always full-duplex ASI interfaces typically transmit at a constant bit rate, hardware-metered ASI interfaces are unidirectional Gigabit Ethernet interfaces are always composed of two unidirectional interfaces, one on each direction
www.tandbergtv.com 7 Timing Recovery Buffer Modulation Clock Recovery RF Clock Time stamps Buffer Fullness Transport Packets ASIModulation Clock Recovery RF Clock Time stamps Buffer Fullness Transport Packets Ethernet Buffer Larger Buffer Required More Complex Algorithm
www.tandbergtv.com 8 Decoder Playback Process (ASI) Buffer Level Time VBV T=0, decoder starts receiving data Decoder starts playing I B BPBBPBBPBBP
www.tandbergtv.com 9 Decoder Playback Process (Ethernet) T=0, decoder starts receiving data Decoder starts playing Buffer Level VBV Time I BBPBBPBBPBBP Packet Reception Times
www.tandbergtv.com 10 Conclusions so far… From a physical layer point of view, ASI and Ethernet are very similar –Point-to-point packet transport mechanism Ethernet always has a CRC so bit errors can be detected –With ASI, even if configured for 204-byte mode (Reed- Solomon), the great majority of the equipment does not generate or check it – that is done by modulators and demodulators. Differences in packet timing are very manageable But … what about packet loss???
www.tandbergtv.com 11 The Packet Loss “Issue” Let’s look first at a point-to-point connection with a crossover cable. There is no contention, no buffering – it is almost the same as having two ASI connections, one in each direction. The only way a packet can be dropped is if the receiver drops it – and that is not going to happen (by design)!
www.tandbergtv.com 12 Ethernet Switches All modern switches are non-blocking and can operate at line rate. Transmit and receive channels are independent. Switches also have a certain amount of buffering. Ethernet Port Ethernet Port Non-Blocking Switch Fabric Ethernet Port Ethernet Port
www.tandbergtv.com 13 Where is the Packet Loss, then? Packet loss happens when a link is oversubscribed – more traffic than its capacity. Switch will buffer instantaneous bursts, but cannot buffer forever. Solution: don’t do it!! Switch Data Source Data Source Link Capacity: 10 Mb/s 6 Mb/s 2 Mb/s Packet Loss
www.tandbergtv.com 14 Packet Loss Notes Packet loss happens when there is congestion in the network. Short-term congestion introduces jitter (as packets are buffered); long-term congestion introduces packet loss. Congestion is avoided by properly designing the network capacity for the traffic. Good news is that, unlike data, digital video capacity requirements are well-known and easy to design for. If you want to mix video and data in the same network, high-end routers and switches can be configured to give priority to video.
www.tandbergtv.com 15 Dealing with Occasional Packet Loss Occasional packet loss, for whatever reason, can be handled by FEC. –Slightly different from the traditional FEC – we rebuild “lost” bits instead of “correcting” wrong bits. Standardized FEC options: –RFC 2733: “Row” FEC. –Pro-MPEG FEC: “Column” and “Row” FEC, can handle burst losses. FEC is supported in most Tandberg equipment and interoperates with equivalent implementations from third-party vendors –Interop demonstrated in VSF meeting in Orlando last January.
www.tandbergtv.com 16 IP Advantages over ASI We have seen that, from a transport point of view, IP and ASI are fairly equivalent, with a small advantage in favor of IP (FEC). As a system interconnect solution, IP has two major advantages over ASI: –IP has a network layer: IP packets contain routing information, indicating where they should go. That includes IP multicast – one-to-many delivery. –IP equipment is universal, and there are many vendors to choose from – high volume items, very cost- effective.
www.tandbergtv.com 17 ASI Interconnect Video Source ASI Modulator Decoder ASI Video Source ASI Video Source ASI Modulator Decoder ASI Modulator Decoder ASI Switch $$$$$ Control Terminal Required since Transport packets do not carry addresses
www.tandbergtv.com 18 IP Interconnect Video Source Ethernet Modulator Decoder Ethernet Video Source Ethernet Video Source Ethernet Modulator Decoder Ethernet Modulator Decoder Ethernet Switch cheap Control is not required since each packet contains an address!!
www.tandbergtv.com 20 Ingress: Encoders All Tandberg Encoders either have IP output built in (iPlex, Mediaplex) or offered as an option (EN series) EN Series iPlexMediaplex
www.tandbergtv.com 21 Encoders at a Glance EN Series (single channel) SDTV/HDTV – MPEG2/MPEG4 –EN5710/5720: MPEG-2 Standard Definition –EN5770/5775: MPEG-2 Standard Definition Dual-Pass –EN5780/5782: MPEG-2 High Definition –EN5920: Windows Media/VC-1 Standard Definition –EN5930: H.264 Standard Definition –EN5980: Windows Media/VC-1 High Definition –EN5990: H.264 High Definition –EN8030: Second Generation H.264 Standard Definition –EN8090: Second Generation H.264 High Definition Mediaplex, iPlex (multiple channel) –MPEG-2 Standard Definition Submodule (up to 48 in the Mediaplex, up to 8 in the iPlex) –H.264 Standard Definition (up to 48 in the Mediaplex, up to 8 in the iPlex) –H.264 Second Generation Standard Definition (up to 4 in the iPlex, Mediaplex support planned). –H.264 High Definition (up to 4 in the iPlex, Mediaplex support planned)
www.tandbergtv.com 22 Network Interfaces and Protocols Interfaces: –EN Series: Dual copper Gigabit Ethernet Interfaces –iPlex: Dual Gigabit Ethernet (SFP – fiber and copper available) –Mediaplex Four Gigabit Ethernet Interfaces (multimode fiber) –Mediaplex/iPlex also support optional ATM OC-3, DS-3 and E-3 interfaces. Protocols: –UDP –RTP –Forward Error Correction
www.tandbergtv.com 23 Receivers at a Glance All Tandberg Receivers include a Professional Decoder Receivers have a variety of available input front-ends (including IP), optional descrambler, and an ASI output The TT1222 includes an IP output option. TT1222: MPEG-2 SD 4:2:0 TT1260: MPEG-2 SD 4:2:2 TT1280/2: MPEG-2 HDRX1290: Everything
www.tandbergtv.com 24 Process: Multiplexers and Demultiplexers Capable of multiplexing and demultiplexing IP flows. Extensive set of (P)SI table generation options Functions also available on ASI. Mediaplex iPlex MX8400 High-end multiplexer, GE inputs and outputs Scrambling also available
www.tandbergtv.com 25 Process: Rate Shaping Rate Shaping: Converting a service from one bit rate to another –To fit in a bandwidth-limited channel –Convert to CBR for video servers Function provided by the Media Processor submodule in iPlex/Mediaplex –Mediaplex: support for approximately 144 services. –iPlex: support for approximately 36 services. –Actual number depends on bit rate Inputs and outputs can be IP streams Mediaplex iPlex
www.tandbergtv.com 26 Process: MPEG-2 to H.264 Conversion Most existing content from broadcasters comes in as MPEG-2. In some installations, it may be desirable to convert it to H.264. The Media Processor submodule in the iPlex/Mediaplex can provide this function. Capacity: –Mediaplex: 48 services –iPlex: 8 services Inputs and outputs can be IP streams. Mediaplex iPlex
www.tandbergtv.com 27 Conclusions There are devices available for the entire digital video processing chain that can use an IP network as the interconnection method. This IP interconnect can be restricted to the head-end or can extend all the way to the consumer set-top box. IP interconnects can be used in traditional digital video architectures (digital cable, satellite) inside the head-end, while maintaining the same egress method. Tandberg Television has all the “bits and pieces” required to make this work!
www.tandbergtv.com 28 Obrigado! Carlos Capellão firstname.lastname@example.org Tel. 21.2493.0125