Audio engineer warns of potential PRO channel interference from data insertion

Eric Small, CEO and head of technology for Modulation Sciences, has warned the FCC that data insertion by a company called Dotcast could cause interference with the audio PRO channel that broadcast stations use to communicate between crew members during electronic newsgathering activities. Although it’s authorized, Small is urging that Dotcast’s technology be properly tested before going into widespread use.

Dotcast, based in Mountain View, Calif., is a privately held company that has developed proprietary technology which uses existing terrestrial broadcast spectrum and cable TV signals to distribute movies on demand, music jukeboxes, game arcades, software applications, sports programming, financial services and e-learning data by inserting 4.5 Mbps of data into participating stations’ analog television signals and home computers. To receive the data on their TV or PC, consumers and businesses must install a special set-top box on their TV or reception card on their computer.

Thus far Dotcast has tested the technology in September and October of 2001, under Special Temporary Authority from the FCC, at the ATTC facility in Alexandria, Va. It has not been widely deployed, however, so the PRO channel problem, which could negatively affect technical crews’ IFB communications channel, has not been fully realized.

Modulation Sciences' Model MSI-3300 television audio processor AES/EBU/Analog (TOP) and SAP receiver. The company warns that a new system may cause signal interference to operations of BTSC stereo, BTSC SAP and/or BTSC Pro channel components of the NTSC television signal.

As broadcasters begin digital transmission, Dotcast said it will use the new DTV towers to expand its network capacity and insert data into a digital television signal at double the speed, up to 10 Mbps, which Small said could become even more of a problem. It does this, Dotcast said, to overcome technical obstacles that make the Internet an impractical network for delivering broadcast-quality video and other large data files. Dotcast claims to have multiple broadcast partners in every major TV market, and that in one 24-hour period with two towers in a single market, its network can distribute gigabytes of data--25 DVD-quality feature-length movies, 500 CD-quality full-hour music albums, and hundreds of video games, e-books, software applications--and still have capacity left over within that 4.5 Mbps to continuously update the top 100 Web sites.

In filings on February 12, Small accuses Dotcast of providing field test results in a manner not normally done with such circumstances. While the physical files are available for copying at the FCC’s headquarters in Washington D.C., no electronic versions are available anywhere.

"They’ve done everything possible to keep a low profile with this," said Small. "None of their documents and none of the ATTC documents relating to Dotcast’s technology are available on the Web or anywhere else. This is not standard practice. Usually everything is available electronically. Perhaps they have something to hide," he said.

With a vested interest since his company makes PRO channel equipment, Small said he traveled to Washington D.C. to review the documents and was horrified at what he read. Dotcast, in his view, has completely ignored OET-60 [a FCC document that explains how field tests should performed] and what should be and the importance of the PRO channel to broadcasters.

Yet, they have not done anything illegal, Small is quick to add. "What they have done is chosen to maintain the lowest possible profile because they don’t want people to understand that their service trashes the SAP [supplemental audio programming, i.e., foreign language simulcasts] and PRO channels."

Small is asking the FCC to make sure the Dotcast system does not cause interference to broadcast operations of Broadcast Television Systems Committee, stereo, audio, BTSC SAP and/or BTSC PRO channel components of the NTSC television signal.

Small said his concerns arise from Dotcast’s use of the aural baseband as a component of its data injection system. After reviewing Dotcast’s plan--filed initially with the Commission on November 1, 2001, with a follow-up letter (and accompanying test results) submitted on December 27, 2002--Small said, he noted there was no indication that any aural tests were performed with companding (basically, a noise reduction technique) removed, as is required under FCC OET-60 rules. As a result, it is impossible to determine whether Dotcast’s system complies with the technical standards, said Small. The FCC should withdraw [Dotcast’s] authorization until the testing is done in compliance with the OET-60 ruling.

If companding systems are subjected to more noise than they are designed to cope with, he said, those systems will suddenly cease providing any noise reduction at all and the channel becomes unusable.

"My review indicates that the Dotcast documents contain no discussion at all of the PRO channel or the possible impact which operation of the [Dotcast] system might have on that channel," Small told the FCC in his filing. "This is a matter of particular concern because the PRO channel is vital to many stations as an essential element of their electronic newsgathering (ENG) activities."

Small said about 300 stations, mostly in major markets, utilize the PRO channel and that there are no suitable substitutes for use of PRO channel, especially for ENG.

"Land mobile channels are too scarce, and their signal reach too limited, to accommodate the extensive sharing which would be necessary to cover a major news event," his filing reads.

He also said that no other datacaster interferes with the aural portion of the broadcast TV signal. There are, however, several datacasting companies that have caused interference on the video side.

Since the end of 1999, when it received initial authority to operate in Scottsdale, Ariz., Dotcast has been trying to put together a high-speed wireless broadband network capable of delivering hundreds of gigabytes a day of rich media and other digital content. They later received authorization in March 2001 to test the service on channel 61 in Seattle, Wash. By joining the Dotcast Digital Network, broadcasters enable Dotcast to utilize parts of their over-the-air digital spectrum at certain dayparts to offer paying clients a distribution channel for delivering their products and services directly to Dotcast’s consumer and business subscribers. In each participating local broadcast facility, Dotcast installs distribution servers with proprietary technology that inserts data into the unused analog or digital over-the-air broadcast signal without interfering with the normal programming, according to company literature. In return, broadcasters share in the revenue Dotcast earns from companies using the Dotcast Digital Network.

Modulation Sciences, based in Somerset, New Jersey, is a provider of BTSC stereo and television audio and video monitoring, FM audio processing and FM audio subcarrier products. The company was instrumental in defining the North American standards for BTSC stereo broadcasts and has developed an over-the-air demodulator for DTV signals that it will demonstrate at the NAB convention next month.

The FCC would not comment on when it might review Small’s filing and make a ruling. Repeated calls to Dotcast were not returned as of press time. For more information, visit Modulation Sciences at and Dotcast at

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