The EBU (European Broadcasting Union) formed project groups to tackle the specific issues around contribution over IP for radio and TV.
“It’s clear IP networks will be replacing broadcast specific networks - the withdrawal of ISDN which is fundamental for audio contribution is an example - so we set up the audio group to tackle audio over IP standards, and we’ve now initiated a video over IP group to do the same for TV contribution, and also look at the control of broadcast equipment via networks” says Rhys Lewis, chief enterprise architect of the BBC, and chairman of the EBU Networks committee. The video over IP group will be soliciting the views of broadcasters and manufacturers at IBC in September on the market requirements for a standard.
“We’re working towards a new audio over IP interoperability standard being in place this autumn, which 15 manufacturers have already endorsed, and eight or nine are on the way with early implementations, creating interoperability between previously incompatible systems” says Lars Jonsson, technology strategist at Swedish Radio, who chairs the EBU project group N/ACIP, Audio Contribution over IP.
Joint meetings between broadcasters and manufacturers, which began last year at IBC, saw a draft recommendation approved, which some have already begun to implement in their kit.
One of the drivers of the project was to avoid the interoperability problems around ISDN, as audio over IP replaces it. Sweden and the UK will be the first to lose ISDN.
“It’s been hit and miss with ISDN for twenty years, since no-one agreed on a real standard in that time, so this EBU initiative is certainly going in the right direction to get over that problem for audio over IP” says Greg Massey, chief technology officer of audio processing company APT. His is one of the companies already signed up to implement and test the standard between different equipment. Other vendors include Mayah, Orban, Harris, AVT, Digigram, Telos, Musicam and Tieline in Australia. Eight more are set to join the group.
Along with the standard for audio over IP will be a set of recommended operational practices, to help people decide what settings they need for particular types of links and networks.
BBC Research has been playing a key part in formulating the standard, testing various network configurations and equipment to feed information into the EBU standardisation process. But the audio suppliers have also contributed to the process.
“Some manufacturers have got together to do their own inter-working tests, and they all see the standard as beneficial to themselves as well as broadcasters, in terms of saving cost, time and effort establishing links between different equipment” said Peter Stevens, the BBC Research engineer on the N/ACIP project group.
There will be five base audio codecs defined as mandatory in the standard, with more either recommended or optional, plus a series of recommended practices.
“It will solve the two fundamental problems that ISDN also had, of agreeing the formats sent between equipment, and in defining the establishment protocol to allow different equipment to communicate” adds Massey. “Early next year, we will have interoperability, thanks to this EBU group”
Telecom operators offer an increasing number of IP-based services, and IP networks are expected to gradually offer higher quality and bandwidth. Many IP circuits are carried over SDH/PDH and ATM links. Traditional services such as ATM, PSTN, ISDN, SDH and PDH will eventually be phased out and replaced by IP services over microwave links, copper or fibre. The volume of new services, not only for data communication, but increasingly for voice telephony and TV, are expected to lower the cost of good quality IP connections, which is another factor driving their take-up by broadcasters.
However, before the advent of enough bandwidth to offer guaranteed quality of service for public IP networks, it’s expected that provision of private or virtual private networks for carriage of audio and video contribution over IP is likely to remain the preferred method to ensure robust signals.
Two different types of audio transfer can be used over IP networks, file transfer and streaming audio. So audio over IP is used for distribution over the Internet for both live web radio and for downloading of audio files to consumers.
For professional audio contribution over IP for live transmission, streaming has to be used.
Errors in the IP networks may cause interruptions in the service due to excessive delays or loss of packets. Buffers at the receiving end are used in order to compensate for the uneven arrival time of IP packets. But these buffers can introduce considerable delay, causing a trade-off between acceptable delay and reliable transmission. In addition, the IP network itself has a delay, which makes it hard to reach the requirement for two-way conversation - a total round trip delay of less than 100ms.
Errors introduced along the IP transmission link are very few in well managed corporate networks. However, with the increasing desire of programme makers to use production methods which use the public Internet for contribution, the error rates introduced can prove disastrous. Methods for reducing the effects of packet errors, such as Forward Error Correction (FEC) and error concealment are in the early stages of development for high-bit rate broadcast audio, but will inevitably introduce more latency, adding to the problems for live transmission.
At a recent EBU conference on developments in network technology, BBC Future Media & Technology lead technologist Adrian Poole outlined some of the technologies the BBC has been experimenting with for a number of different production scenarios. The BBC Edge connectivity project aimed to take a short to medium term view of the most suitable technologies for the BBC to buy into, in the burgeoning IT/IP world.
“One of the essential requirements was the desire to have technology to allow our programme makers to stay out on location longer, without having to return to base, and without needing too much engineering knowledge to keep the technology going” says Poole, and the project did show commodity networks and IT technology are offering multiple solutions that radio & TV producers can tap into.
One aim of the project was to gather requirements from different production departments in radio and TV to match suitable technologies to specific applications.
Part of the plan was also to strike up strategic relationships with vendors to allow the BBC sight of the product development roadmaps, with the aim of influencing that roadmap if possible.
In broadcast news, for example, the news value of any particular story is usually its significance as news crossed with how fast you can report it. Low quality store and forward over a standard phone is ok if the story isn’t that urgent, but urgent news usually requires a satellite ENG truck. The Edge project saw the BBC using a variety of technologies to find effective alternatives to the traditional methods, and most of these used data in IP form.
3G and HSDPA were used for live audio/video. HSDPA was used alone for live audio contribution.VSAT is already in common use for audio, but here it was tried for live video. WiFi and WIMAX were tried for both live and store & forwarded audio and video.
ADSL was used for live TV as well as store & forward. The BBC worked with Vodafone to test 3G broadband using USB modems, data cards in laptops and wireless routers.
“Vodafone’s roadmap foresees 3G downloads of 7mb/sec and 2mb uploads but for now it’s 1.8mb up and 384kb/sec up” says Poole. However, the experiment proved that using commodity networks for urgent newsgathering will work, unless you’re trying to report a major incident or the location is particularly remote, where cell coverage may be sparse.
As it happens, during the period of the trial, the Virgin rail crash in Cumbria occurred, which saw the first pictures on BBC News contributed from a mobile phone by one its senior managers, who was travelling on the train in question. Caroline Thomson, BBC chief operating officer, was taken through what she had to do with her phone to send the video footage, after downloading a software application BBC News sent to her – the result was the first pictures from the derailed and lopsided train.
“Mobile phone newsgathering worked well in this instance, but once the media circus turned up, the cell network quickly became too congested to use, so we had to look for other routes” says Poole.
VSAT for live video in another experiment proved successful, and as a result the BBC is looking to deploy four VSAT video vehicles. While current VSAT audio vehicles use 128kb/sec up and 64 kb/sec downlinks, the VSAT for live video trial used 1.3mb/sec encoding and worked well for the BBC local newsroom in Tunbridge Wells, Kent.
“It only required six minutes set-up time from arriving on-site to being ready to use” said Poole, “We’ll be deploying two vehicles in London and two across England, and we’re considering upgrading existing Audio VSAT vehicles as first response TV news units, with IP downlink facilities planned for TV Centre” he says.
WIMAX got a lot of attention in the Edge project, and the work on it continues. The first live video from Kabul using WIMAX at 512 kb/sec was accomplished in late 2006, and it enables high quality store & forward, according to Poole, with very agile equipment available that moves easily between locations. Tests were also conducted by BBC Research in London, transmitting from TV Centre to Epsom Downs, and in another test using a National Grid Wireless transmitter in North London to transmit to Broadcasting House in Central London. Throughput of 10mb/sec was obtained in these tests.
BBC Radio is going to lose its VHF news reporting frequency this year, so the BBC is looking to replace it with WIMAX, using the Urban Wimax 4.9GHz licenced service, which features a transmitter in the Westminster area, with good line of sight to BBC News’ Millbank offices. “The WIMAX network also covers most of the political hotspots we’re interested in” says Poole. Urban Wimax offers 4mb/sec up & down links, and the BBC News tests used video at 700 kb, 1 & 2 mb and 2.7mb, with audio at 192kb/sec.
However Poole warns that WIMAX is not yet a mature technology and it could be unpredictable. “There’s still a lot to learn about WIMAX” he says.
The range of different technologies the BBC has used during the Edge project is impressive, including things as diverse as daily reports to Newsnight from the World Cup in Germany, using 3G datacard in a laptop and Vpoint video software, to Springwatch, a very popular live nature series, using live nest cameras every night from three remote locations using DSLmax broadband video streaming. “We’re also using more and more public WiFi hotspots for store & forward or even live if we’ve got the backups” says Poole, but again he sounds a warning: “In the IP world, the technology may be cheap, but it can also have a short life. In some areas, we’ve taken the deliberate decision to wait for the appropriate technology to develop - we need to be careful for instance that we don’t rely solely on public networks for newsgathering - and if we bring in too much streamed IP traffic to the BBC, it could be a problem for our internal corporate network.”