A New Expectation

The DVD Consortium’s mandated audio format for DVD is Dolby Digital 5.1 – a cinema-style surround sound format that envelops the viewer and places them at the centre of the action, thanks to the use of 6 speaker channels in place of the usual two. The use of this format on DVD has led to significant sales of home cinema audio systems in key markets worldwide. For example, over 17.5m home cinema systems have been sold in Europe, with 17% of households in the important UK, German, Dutch and French markets estimated to own a system at the end of 2005. [source: Understanding and Solutions].

This in turn has driven a new expectation of quality surround audio from viewers – which has not gone unnoticed by the broadcast industry. Leading pay TV operators such as Canal Plus, Premiere and Sky are amongst the European broadcasters who have already launched digital TV services complete with 5.1 surround sound. Other entertainment sources are also featuring surround sound – for example games consoles such as the Xbox can generate live real time 5.1 soundtracks that immerse players in their games. And whilst 5.1 sound is a valuable added feature to standard definition media, it’s even more important with high definition; it’s a key feature both of existing HD services in the US and the recently announced services in Europe. So with the expectations of viewers set so high, can IPTV operators really afford to ignore the audio?

Many IPTV implementations have significant data rate constraints, which on first consideration might make it seem difficult to find the extra bandwidth needed to transmit the extra audio channels needed for 5.1. However, adding 5.1 audio doesn’t always require as much bandwidth as first thought. Firstly, it’s not necessary to deliver separate 5.1 and stereo audio streams. Even though the set-top box needs to output soundtracks in 5.1, stereo and mono to suit viewers with different equipment, with Dolby Digital a single data-efficient 5.1 audio stream is delivered to each set-top box and downmixed inside to create any stereo or mono outputs needed. Secondly, next generation audio coders have been designed specifically to partner with new video coders like H.264, offering even more attractive data rates for audio to match the savings for video. This means that home cinema audio can be delivered using data rates practical for IPTV.

5.1 audio can be more of a challenge, however, if it is not planned in from the start. A key consideration is that the right audio technology needs to be included in IPTV set-top boxes from the beginning of deployment. If the right technology is not included at the outset, operators who subsequently decide to offer 5.1 might end up having to ‘simulcast’ separate stereo and 5.1 audio streams to ensure that all viewers can receive audio. It’s also critical that good connectivity is provided to output the encoded 5.1 audio stream to viewers’ existing home cinema systems. As many home cinemas only have inputs for encoded digital audio (rather than decoded multichannel audio), it’s important that the connection format is supported by the maximum number of systems to maximise the audience that can enjoy full surround sound.

Once a platform has been deployed with 5.1 capability, the next step is to source appropriate content. Almost all Hollywood titles and major domestic releases are now created in 5.1, and, due to the demand for 5.1 soundtracks on DVD and increasingly on broadcast services, entertainment series such as Lost, ER and 24 plus premium programming like natural history and documentaries are being produced with thrilling 5.1 sound.

Broadcasters are also starting to add the excitement of surround sound to their premium sports coverage. For example, events as varied as the Superbowl and German Bundesliga soccer have been produced and broadcast live in 5.1, transporting the viewer at home right into the middle of the action.

Audio is already perhaps more important in the marketing of TV services than it has ever been before. But the future brings further possibilities – delivery of soundtracks with 7.1 or even more channels, multiple language versions, streamed director commentaries to be overlaid over the main soundtrack and improved audio for the visually- and hearing-impaired to name but a few.

But for today, it’s critical to note that the audience already has an expectation for home cinema audio with their TV entertainment, not internet quality audio. Fortunately, if the audio solution used by their IPTV supplier has been chosen carefully, they won’t be disappointed.

by Jason Power, Market Development Manager, Dolby.