The Media Links MD6000 video transport system has been selected by Swisscom’s Broadcast Division for contribution feeds at the UEFA 2008 European Football Championships being held in Switzerland and Austria from 7 June. The deal has been overseen by Media Links’ regional partner VIDI, and follows a successful similar deployment for Host Broadcast Services at the FIFA World Cup 2006 in Germany.
This might be a routine contract announcement were it not for the technology involved. Media Links claims to offer the only product suite that allows adaptation of video to virtually any network from conventional 270Mbps SDI (serial digital interface co-ax cables for standard definition TV), to resolution-agnostic IP (internet protocol) or synchronous optical networking standards. In the optical camp are the SONET (synchronous optical networking) format used in the US and Canada, and the later SDH (Synchronous Digital Hierarchy) system popular across the rest of the world, now considered to be the de facto standard. This flexibility allows service providers to economically convert and move video across a variety of multi-service networks, the company claims.
The key principle driving Media Links’ approach is that every incoming signal should be divided into standard IP packets prior to transmission. This avoids all the problems stemming from compressed video, says the company, including encode/ decode delays, hidden compression artifacts in the video image, and the painstaking process of matching encoding parameters to video, audio and data signal sources.
“As consumer-driven demand for HDTV reaches critical mass, broadcasters are faced with the challenge of offering HD services at prices equal to standard definition services,” says John Dale III, Vice President, Product Management at Media Links. “Media Links is providing the technology to transport HD and other signals reliably over existing contribution and primary distribution network infrastructures, eliminating the need to install and manage expensive HD encoders and telco adapters,” he claims.
For Euro 2008, Media Links MD6000 transcoders at each venue will adapt the 1.48Gbps uncompressed HD-SDI video camera feeds to IP (internet protocol) format, each ending up as about 1.6Gbps by the time forward error correction (FEC) and IP encapsulation overheads are taken into account. The signals are now ready to be added to the SDH fibre network, which takes the form of a ring carrying two 10Gbps streams using STM-64 (synchronous transport module) and one 2.5Gbps (STM-16) stream from the four stadiums in each country to the International Broadcast Centre in Vienna.
These include pairs of 270Mbps SD feeds compressed into 300Mbps for unilateral contributions as specified by Swisscom, which also stipulated a range of 40km for the fibre network — although Media Links claims that paths up to 80km can be supported in some cases. In reality, all of the hops at Euro 2008 will be well within the lower figure.
The clever technical stuff begins at the IBC. “Bit errors are inevitable with a fibre link, given the packet queues that form in heavy traffic conditions,” according to Dale. Thanks to FEC, the receiving equipment has a fair idea of when something is wrong or missing, and a small buffer at the receiver gives it time to decide one way or the other, he claims.
However it’s a patent-pending system that Media Links calls Hitless Protection Switching that allows corrective action to be taken without the viewer being any the wiser. According to Dale, by carefully numbering each sequence on both arms of the network reaching the IBC, the Media Link system can affect a switchover from main to backup in less than a millisecond.
An important feature is that packets are switched on an ‘all or nothing’ basis, eliminating fragmentary or repeat data. Similarly, lipsync is maintained irrespective of switching, as the audio is embedded into the video (in accordance with the SMPTE 299M standard for 1.5Gbps HD or SMPTE 272M for 270Mbps SD).
“In IT terms, a frame of video changing 25 times a second is an infrequent event,” Dale observes. “By comparison IP switches signals at around 10,000 packets per second, which gives us a better ‘granularity’, in other words smaller events happening faster. This offers the opportunity to respond more quickly to problems as they occur, rather than suffer the loss of a whole frame for instance.”
According to Media Links President Mario Frattaroli, the technology’s reliability in delivering signals is without match. “At the World Cup two years ago,where we made possible live uncompressed HD video from every venue for the first time, not a single video error occurred throughout the entire duration of the month-long event,” he claims. “We are proud once again to be supplying mission-critical equipment to what is an extremely high-profile event in the sporting calendar.”
