Evaluating Alternative DTV Distribution

In the January RF Technology column, I looked at three USB tuners that offer an inexpensive way to monitor ATSC signals.
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Figures
(click thumbnail)Fig. 1: Stream Monitor CC2

(click thumbnail)Fig. 2: ATSC portable screen

(click thumbnail)Fig. 3: KVWB Samsung demo

(click thumbnail)Fig. 4: KVWB Samsung demo receiver shotIn the January RF Technology column, I looked at three USB tuners that offer an inexpensive way to monitor ATSC signals. While the software of two of the three displayed EPG data, specialized software was needed to display PSIP and stream information. I described Rob He-witt's TSReader software in August 2005. Since then, Rob has added new features and now offers TSReader Pro. At a cost of $399 versus $99, it isn't cheap, but it provides features approaching those of analyzers costing several times that much.

TSReader now supports a wide range of hardware and can view digital cable PSIP data when used with the AutumnWave tuners. If you want to decode EIA-608 and EIA-708 closed-captioning data in TSReader, you'll need the Pro version. All closed-caption fields are displayed.

More expensive ATSC stream analyzers can provide detailed reports of PSIP table problems. Rod Hewitt has added a similar feature to TSReader Pro. While the current may not provide the same level of detail as these ATSC stream analyzers, the display on TSReader Pro provides an easy way to see common problems, and I expect its capabilities will increase. See Fig. 1 for a screen shot of the stream monitor and closed-captioning data from KNBC-DT. I induced errors on the recorded transport stream to show how they are displayed.

Another new feature, available in both TSReader and TSReader Pro, is the ability to remotely monitor TSReader and provide data and pictures over a network or the Internet. There are many ways to do this, ranging from JPEG thumbnails to streaming HD. See www.coolstf.com/tsreader for a description of the options.

TSReader will not only decode MPEG-2 streams, but also MPEG-4 and VC-1. At NAB last year, I was able to view the unencrypted MPEG-4 programming that USDTV was transmitting on a local DTV station. At CES in January, I was able to view and capture the transport stream on KVWB, DTV Channel 22, that Samsung was using to demonstrate A-VSB. More on that later!

STREAMSLEUTH

In my last column, I incorrectly called AutumnWave's receiver TSReader Pro package “SignalSleuth.” The correct name is “StreamSleuth.” As of late January, the cost of the package was the same as the cost of the receiver and TSReader Pro separately, although it is more convenient and you are sure the two products will work together.

The technical support manager for AutumnWave told me developers had been asked to create a large signal-level/SNR window similar to that offered in DVICO's Signal Checker program. AutumnWave is looking into adding closed-captioning support to their software. Since closed-captioning data is already available in TSReader Pro, it seems AutumnWave and Rod Hewitt should be able to work together to bring closed captioning to AutumnWave's “OnAir HDTV” program.

ATSC tuners were everywhere at this year's Consumer Electronics Show in Las Vegas, although they weren't always obvious. As of March, FCC rules require that all TV sets and devices with off-air reception—such as VCRs and DVD recorders—have ATSC tuners, so it was hard to find analog-only TVs. I saw one Asian manufacturer showing small, inexpensive, analog-only TV sets. AudioVox had an ATSC receiver in its small screen under-counter DVD and TV sets. I didn't find any handheld ATSC receivers other than the Samsung prototype. Super-Union Multimedia Corp., however, was showing a mock-up (using a cardboard frame, of a portable ATSC receiver. See www.sumc.com.tw/ for more information. Fig. 2 shows a picture of it. Perhaps we'll see this system in a consumer product next year.

Zenith/LG and RCA/Thompson were both showing ATSC set-top boxes. The Zenith set-top box combines the fifth-generation demodulator and other circuitry (except the tuner) on one IC, reducing manufacturing costs. While the set-top box is not available now, DVD recorders with fifth-generation chipsets are now available. Both Zenith and RCA were showing set-top boxes hooked up to early color TV sets with rotary-dial tuners, assuring customers that come February 2009, they won't have to throw out their old TV. RCA said their set-top box would initially cost $200 but expected the price to drop to $50.

Although LG announced a sixth-generation ATSC chipset before CES, they weren't talking about it in their booth. Thomson implied the new RCA USB tuner, that I described earlier in my RF Report on CES, would work better than the Pinnacle HD Stick Pro fifth-generation tuner, but couldn't say what chipset was being used. I hope to receive a unit to test and will report on the performance after I've had a chance to try it in a few different cities. Unlike the tuners I reviewed in the last column, the RCA USB tuner will include closed captioning. It is also supposed to work with processor speeds down to 1.5 GHz. It includes an antenna with a 6 dB preamplifier, which should improve performance.

Micronas introduced a line of ATSC demodulators last year and showed a smaller, better and cheaper design this year, but so far, except for one PCI tuner, I'm not aware of them being used in any products available now. The Auvitek AU852x series of chips with a sixth-generation demodulator design incorporating Auvitek's patent-pending FADE (fully adaptive demodulation and equalization) technology looks interesting.

I've often said portable and perhaps mobile reception of broadcast DTV is important for the future of over-the-air TV. With home TV sets hooked to cable or DBS, broadcasters have to compete with a hundred or more programs, and an increasing number are becoming available in HD. For wireless reception, broadcasters, with 19.39 Mbps of bandwidth per channel, are in a stronger position. Will these sixth-generation designs be sufficient to allow reliable portable and mobile operation? Perhaps additional training data, like SRS in the proposed A-VSB standard, will help.

At CES, Samsung transmitted an A-VSB signal over KVWB on Channel 22. Fig. 3 shows a screen capture of TSReader Pro displaying PSIP and stream information. Note that due to the mapping of the SRS (supplemental reference signal) and turbo stream at the packet level, the data rates in Fig. 3 will not reflect the A-VSB overhead. I had a chance to play with one of the handheld receiver prototypes while riding around Las Vegas in Samsung's demo bus. Fig. 4 shows the receiver and the image it was receiving inside the bus, in motion, with both antennas collapsed.

The robustness of the signal was amazing—I had to hold it near the floor of the bus, antennas collapsed, to freeze reception for a few seconds.

Is A-VSB the solution? Perhaps, but the SRS and quarter-rate coding on the 750 Kbps MPEG-4 stream in the demonstration consumed a significant part of KVWB's DTV bandwidth. The SRS can use as much as 2.89 Mbps. After subtracting the bandwidth required for one robust channel (3.3 Mbps) and SRS, a bit more than 13 Mbps remains for other programming. While this may be enough for HDTV, it doesn't allow much room for other multicast channels.

Additional testing is being done on A-VSB. New demodulator chips may allow adequate performance with less bandwidth devoted to SRS. Perhaps less robust encoding can be used on the turbo stream. We should know once the testing is completed.

Overall, I was encouraged by what I saw at CES this year. Over-the-air ATSC reception was available in more devices. ATSC development seemed robust, not only with breakthrough technology like Samsung's A-VSB but from manufacturers committed to improving ATSC reception, and OEMs like SUMC offering interesting products like their portable TV design. It will be interesting to see how much of this new technology makes it into consumer products at CES2008.

As always, comments and questions are welcome. E-mail me at dlung@transmitter.com.