Dolby Laboratories doesn’t sell anything directly to telecom service providers, but the well-known creator of high-quality audio technology is trying to get a message across to those who would offer IPTV.

That message is simple: When delivering IPTV over MPEG-4 or H.264 technology, the correct audio format is Dolby Digital Plus.

“It’s a more efficient codec with more bells and whistles,” said Fadi Malak, senior market development manager for Dolby. That includes a wider operating range and finer resolution of data rate control as well as a higher number of audio channels than the current 5.1 – that’s five main channels plus a low frequency effects channel that is the “.1” in Dolby Digital. And it is a complementary format to today’s HD-DVD and Blu-Ray disc high-definition systems, he adds.

“Since IPTV is a new service, they are looking for differentiators,” Malak said. “Dolby Digital Plus enable them to take advantage of 7.1 channel surround sound that is being adopted by HD-DVD and Blu-Ray disc systems. They can sell that, using the Dolby name, as a Blu-Ray-like service.”

There are also other features such as interactive mixing of two different audio tracks. Set-top box makers worldwide are building Dolby Digital Plus into their systems, he added. The new technology is based on the existing multichannel coding format, known as AC-3, and is backwards-compatible with Dolby Digital.

Another advantage of Dolby Digital Plus is that it has greater coding efficiency that allows it to perform at lower data rates by using a variety of improved techniques for filtering, quanitization, channel coupling, spectral extension and something called transient pre-noise processing.

Dolby’s audio technology is built into every DVD and is in used in 73 million set-top boxes worldwide. It is used by content creators, at the super head-ends of service providers, at live broadcast sites and in the home, where it is “in every audio-video receiver ever made,” Malak states.

That end-to-end connection enables Dolby to do things such as control loudness so that moving from one channel to another, or sitting through commercials, doesn’t require constant adjustment of the volume. That kind of control is possible, Malak said, because of the use of metadata along with the Dolby formats.

“Used properly all along the chain, we can control the quality of the sound,” he said. Problems arise, however, when actions taken within the network alter or disrupt that metadata. “We need to ensure the metadata path is maintained.”

That’s relevant for IPTV players because many of them are dealing with bandwidth constraints in their network and the temptation is there to do things such rate-shaping, which buffers packets that are above the available transmission rate, rather than dropping them. Rate-shaping interferes with the metadata path and can lead to lower quality audio, Malak said.

“We would rather that they use Dolby Digital Plus which is designed for H.264 compression than use rate-shaping,” Malak said. Satellite and cable offerings have conditioned customers to expect a certain sound quality, he said.

“If you start compressing to save bits, people will notice and complain,” Malak said.

Dolby is particularly concerned because some IPTV players are initially focused primarily on just getting the video right, almost as a me-too service, he added, with plans to address such things as high-definition TV and service quality as a second priority.

As part of its push for Dolby Digital Plus, the company also is emphasizing what having 7.1 audio channels, versus the current 5.1 channels, will do for the new home entertainment centers with their big flat-screen panels and surround sound systems.

“7.1 gives you more surround sound, it fills in the gaps,” Malak said. “Audiophiles will detect it.”