The Impact of the FCC's Broadcast Flag on Demodulation

[Gregg Lengling]

I spent this weekend reading through the FCC Report and Order and Further Notice of Proposed Rulemaking (FCC 03-273) on the Broadcast Flag looking for details on how it will affect broadcasters. For background, see the TV Technology article - FCC Approves Broadcast Flag - describing the FCC's action and the controversy surrounding it.


One thing that surprised me was that there was no specific exemption for professional broadcast DTV demodulators or test equipment. The definitions in 73.9000 do not offer much help, stating, "Demodulator means a component, or set of components, that is designed to perform the function of 8-VSB, 16-VSB, 64-QAM or 256-QAM demodulation and thereby produce a data stream for the purpose of digital television reception." Makers of professional demodulators and test equipment could argue that this equipment is not "for the purpose of television reception," but that could be difficult. Professional demodulators that offer an HD-SDI output certainly seem to be out of compliance. Demodulators that offer the entire transport stream, using SMPTE 310 or ASI protocols, with the broadcast flag intact, may be okay, but if the transport stream is considered to be "marked content," then, to comply with the new rules, it may have to be encrypted so that it passes to the demodulator (ATSC stream analyzer and data recorder, for example) by a "robust method."


A covered demodulator can pass "Marked Content" only to outputs specified in FCC Rule 73.90049(a). These include an analog output, an 8-VSB, 16-VSB, 64-QAM or 256-QAM modulated output (with the Broadcast Flag retained), a digital output "protected by an Authorized Digital Output Protection Technology," and output to another product where "such Covered Demodulator Product exercises sole control (such as by using a cryptographic protocol), in compliance with the Demodulator Robustness Requirements, over the access to such content in usable form in such other product," an output for the purpose of making a recording of "such content pursuant to paragraph (b)(2) of this section, where such content is protected by the corresponding recording method, or where the product is incorporated into a computer product and the unprotected output is an image having the visual equivalent of no more than 350,000 pixels per frame (i.e. 720x480 pixels) and 30 frames per second." The rules are silent about treatment of ASI and SMPTE 310 outputs and even HD-SDI outputs.


GNU Radio, a software based receiver I wrote about in TV Technology that can be programmed to receive and decode HDTV broadcasts, seems to be excluded if the output if not piped to a DVI interface at greater than 350,000 pixels, but would fall under the rules if the MPEG-2 stream is recorded on a hard disk. Software tools are included in Section 73.9007 - Robustness Requirements for Covered Demodulator Products. The GNU Radio software could run into trouble here as 73.9007 requires "The content protection requirements set forth in the Demodulator Compliance Requirements shall be implemented in a reasonable method so that they cannot be defeated or circumvented merely by an ordinary user using generally-available tools or equipment." A note to rule explains: "Generally-available tools or equipment means tools or equipment that are widely available at a reasonable price, including but not limited to, screwdrivers, jumpers, clips and soldering irons. Generally-available tools or equipment also means specialized electronic tools or software tools that are widely available at a reasonable price, other than devices or technologies that are designed and made available for the specific purpose of bypassing or circumventing the protection technologies used to meet the requirements set forth in this subpart. Such specialized electronic tools or software tools includes, but is not limited to, EEPROM readers and writers, debuggers or decompilers."


It will be interesting to see if test equipment or professional demodulator manufacturers request an exclusion from the Broadcast Flag requirements. I did not see any of the major DTV test equipment manufacturers listed under parties filing comments or reply comments in the Report and Order.


If you are wondering what impact the Broadcast Flag will have on DTV station operation, a lot will depend on whether the station implements the Broadcast Flag. The FCC gives broadcasters the right to opt out of transmitting the Broadcast Flag, but network and syndicated program providers are likely to insist on it, at least for HD material. Existing software for inserting PSIP information in the transport stream should be able to be easily upgraded to support the Broadcast Flag, if it doesn't have this capability already. This information would ride along with the program data, just as ratings information and closed captioning do now. This could cause some problems for stations running static PSIP (one "program" for the entire broadcast day), but these stations are likely to be simulcasting their analog standard definition product and thus will not likely be pressed by program suppliers to include the Broadcast Flag. It is possible some set-top boxes may block programs with the Broadcast Flag set and this could lead to viewer complaints. Please drop me an e-mail if you hear of DTV tuners not responding properly to the Broadcast Flag.
By Doug Lung from his report.

[hoppingbuffalo]

Hi, good post Gregg and, as it says at the bottom of your post, "Please drop me an e-mail if you hear of DTV tuners not responding properly to the Broadcast Flag."  What is the email address you intended people to send to?  Here's what I would email:

My new Panasonic DVD recorder (with ATSC tuner - my old VCR died) sometimes says a noisy NON-PROTECTED progam is copy protected.  I'm pretty sure this is the reason because I get a copy protected message in the middle of the program randomly (same program, different broadcast times).  While not an RF engineer, I am a physicist and did semiconductor R&D.  An unintentional and inadvertent broadcast flag on a noisy NON-PROTECTED program is the only explanation that makes scientific sense.

Here's my question for you.  What does the FCC require?  Does it require that if a solitary frame comes through with a broadcast flag equipment halts copying?  Or, in the interest of accurate detection, an equipment maker may wait for up to 30 (or 60, 90, 3600, etc.) consecutive frames before it decides the program is, indeed, copy protected?  Or may an equipment maker resume copying once the broadcast flag ceases to be detected?  Or some other noise elimination - including noise elimination on the broadcast flag signal?

IMHO, even if we're stuck with the broadcast flag, demodulators (or demodulators embedded in a DVD recorder) need to do a better job of accurate detection.

I know closed captioning is on a "sub signal" and it's prone to noise.  Sometimes I can't read it.  It's reasonable to presume the broadcast flag is prone to noise as well.

Jim