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  • DCTV: The Next Generation?

    With DEFCON rooms now spread across eight hotels, I had a crazy idea for evolving DCTV: broadcast it over the air. It seems like everyone and their dog has one of those RTL SDR dongles, which can demodulate DVB-T/COFDM in hardware. With one of these dongles, you could tune in to DCTV anywhere you'd like--in your hotel room, in a taxi, at the airport, etc.

    Of course this raises a number of questions:

    1. Could/should this be done using the amateur service? The voluntary ARRL band plan has several allocations for ATV, which I bet are mostly unused. But would it be discourteous to sit on a 6 MHz channel for a few days? Would this content qualify as an "information bulletin" and thus be allowed to be transmitted one-way? It certainly wouldn't be of interest or even receivable by the general public. Could it be perceived as being commercial in nature, supporting and/or promoting the for-profit enterprise known as DEFCON? On the other hand, it does seem like it serves the some of the official purposes of the amateur service well--advancement of the radio art through developing and distributing tools to enable others to easily transmit DATV (which could be potentially be used to support emergency communications in the future) as well as expanding the pool of people who understand and can use modern digital radio techniques.

    (The current amateur rules require you to ID every ten minutes using a supported modulation scheme, which doesn't include any sort of digital TV system. However, I have successfully been able to transmit ATSC *and* an AM-modulated phone ID by modulating the ATSC pilot tone. It seems to have no impact on the digital reception, and the ID can indeed be heard on an analog radio. This is getting pretty close to "advancing the art"--commercial stations are beginning to investigate whether they can simultaneously transmit ATSC and FM on channel 6. Many channel 6 LPTV stations are still analog because most of their audience is listening to the audio on 87.7 FM. There seems to be a fair bit of drama over the FCC's upcoming digital transition requirement for LPTVs.)

    2. If it doesn't seem appropriate to operate DCTV under the amateur service rules, would it make sense to apply for a Special Temporary Authority (STA)? AFAIK, this could either be a waiver of certain amateur service rules, or a temporary authorization to operate in some other part of the spectrum (e.g. a vacant TV channel). This doesn't seem too hard--Shadytel has successfully obtained STAs to operate their GSM network at Toorcamp 2012 and 2014.

    3. Is it even technically feasible? I haven't done the math to figure out what kind of power you'd need to cover the DEFCON hotels area. Plus I bet indoor reception is awful. I've seen guides to compute the "city-grade" contour of ATSC signals, but I'm not sure how DVB-T coverage compares. (We could use ATSC, but the RTL dongles can't receive ATSC.) One nice thing about DVB-T is that you can set up a Single Frequency Network, where a bunch of lower-power transmitters are synchronized so that they don't interfere with each other. SFN techniques could be used to fill in weak spots/dead zones inside Paris/Ballys, for example. However, getting cheap SDR peripherals to support SFNs might be too ambitious. (I'm thinking of a setup where a HackRF transmitter has its sample clock fed by an external GPS receiver, and modifying the firmware to use the GPS PPS signal to precisely sync up the sample buffers.) There's also the issue of distributing the content to the SFN transmitters.

    4. Do people have the equipment/resources to support this? I've managed to transmit ATSC with my HackRF, so generating a signal doesn't seem too difficult, but transmitting it any reasonable distance is another story. You'd need a decent linear amplifier, antenna(s), and probably some filters. We'd also have to find a place to set up a somewhat powerful transmitter.

    Assuming it's legally and technically feasible, I think it could be pretty awesome. All of the tracks could be multiplexed onto one digital channel. If there's a way to get slide video, those could also be on separate subchannels. Real-time caption data could also be fed into the channels. And of course, there might be some excess bandwidth that could be used for... whatever.

    And yes, I did say this was a crazy idea...

  • #2
    I posted a link to this on twitter, which lead to a few retweets and favorites, and this reply:

    URL1=https://twitter.com/pmocek/status/559401029117022208

    Originally posted by URL1
    Phil Mocek ‏@pmocek

    @TCMBC @supersat DVB-T broadcasts were available at 31c3. I heard nothing about how it went, but details are here: https://ccc.devsn.se/congress/2014/wiki/Projects:DVB-T
    If you are risk-averse to accepting a Cert not blessed by a CA in your browser, a summary of that wiki-like entry:

    URL2=https://ccc.devsn.se/congress/2014/wiki/Projects:DVB-T

    Originally posted by URL2

    Description: DVB-T on Channel 22, 24, 26 from three location in CCH. 3 Transmitter SLX8000 with EIRP 27 dBm on selfmade J-Antenna. Streaming from all talks will be packed in an ASI Stream.


    Details: This will be a test szenary for the 2015 ccc camp. Planed there is also HD Streaming with DVB-T2 standard (Non HVEC). On this event we will test the integration to VOC hardware and use standard DVB-T. The streams will be multiplexed an play out as an ASI Transport Stream with a DecTek 145 dual out ASI PCI card. An ASI multiplier splits this this in three lines and we use installed Video network in the CCH to the transmitter location, on ground, between one and secound flor and also one in thirs flor. Please feel free to use and we also interestet on feeedback.
    May be we can use this also for Infoscreens on TV cable network on CCH
    Obviously, once copied/pasted, this data is static. Any updated, revisions or feedback they add are on their site. Follow their link for the latest on this.

    Comment


    • #3
      Interesting... Ze Germans are always one step ahead! ;)

      I don't think there's any question about whether *a* signal can be generated. (I may develop a low-power proof-of-concept shortly.) Whether it's feasible to distribute this signal widely is another thing altogether. There are both policy/legal questions, which are necessarily US-specific, as well as technical questions (e.g. how well can you pick up TV signals inside Vegas hotels and casinos?).

      Comment


      • #4
        There's a few concerns I have with this project.

        1) Broadcasting something powerful enough to punch through walls even of the convention center is going to be difficult. We've had a hell of a time with ham radio (voice), and we're moving to a (small) repeater because of it for this year. The convention center is, to my knowledge, down in the basement beneath the two hotels; generating anything that goes up to the rooms is going to take a *lot* of power. Generating that much power is going to be *extremely* expensive (as in, the ham radio amplifiers necessary to send those signals)---and remember that ham radio TV is nearly 100% duty cycle, so you'll need a really, really good amplifier for it. (Alpha: just put a brick on your wallet and never touch it again.)

        2) So I am in fact a lawyer, but I don't do ham radio stuff as law stuff, and the following is not legal advice. (And you're gonna want some before you try this, so keep that in mind.)

        CFR 97.113 (part of the rules applicable to ham radio) reads in part: (There's a copy available at http://www.arrl.org/files/file/FCC%2...023%202014.pdf )

        (b) An amateur station shall not engage in any form of broadcasting, nor may an amateur station transmit one-way communications except as specifically provided in these rules; nor shall an amateur station engage in any activity related to program production or news gathering for broadcasting purposes....

        Broadcasting is defined earlier as communications intended for the general public (that is, non-hams).

        By the way, when you look at all the exceptions for one-way communications "specifically provided in these rules," you get exceptions for things like beacons and telemetry; those are how APRS works. None of those are applicable to ATV.

        So by my reading, this is absolutely one-way, and is absolutely a broadcast---and both are prohibited for what you're trying to do. Given that there are sometimes other experimenters on the radio bands at DEF CON, the last thing we want to do is broadcast something so large that it nearly compels action from either FCCAA OOs (for non-hams: the FCC Amateur Auxiliary Official Observer program, the people who volunteer to sniff around for incorrect/illegal use of the airwaves) or, in the worst case, the FCC itself. That'll make no one happy.

        3) While you could in theory apply for STA, that's a big ask for the FCC; STAs are easy to grant for things like ToorCamp's ShadyTel and Burning Man, because *nobody is there*. In the middle of Las Vegas, that's much harder.

        4) Even if you had approval, weren't breaking ham rules, and could buy enough equipment to broadcast strongly enough to be heard---very, very few people could pick you up, with the right combination of hardware and software, and knowledge to actually do it.

        So: I'd vote no, not because it's not a neat idea (it is), but because the negatives, IMO, outweigh the positives.

        Comment


        • #5
          Would the Bally's and/or Paris allow use of their internal TV broadcasting system? I think the answer there likely lies somewhere in between "no" and "hell no"

          Personally, i was impressed with some folk in the past who had talked about using network streaming for some of the talks. If there was a way to do that so that people could view from the rooms and suites, that'd be pretty cool. But, then again, DEFCON has grown so much beyond that now.... even this is not really feasible as a value-add anymore, possibly.


          "I'll admit I had an OiNK account and frequented it quite often… What made OiNK a great place was that it was like the world's greatest record store… iTunes kind of feels like Sam Goody to me. I don't feel cool when I go there. I'm tired of seeing John Mayer's face pop up. I feel like I'm being hustled when I visit there, and I don't think their product is that great. DRM, low bit rate, etc... OiNK it existed because it filled a void of what people want."
          - Trent Reznor

          Comment


          • #6
            Originally posted by Deviant Ollam View Post
            Would the Bally's and/or Paris allow use of their internal TV broadcasting system? I think the answer there likely lies somewhere in between "no" and "hell no"

            Personally, i was impressed with some folk in the past who had talked about using network streaming for some of the talks. If there was a way to do that so that people could view from the rooms and suites, that'd be pretty cool. But, then again, DEFCON has grown so much beyond that now.... even this is not really feasible as a value-add anymore, possibly.


            A better question would be, which hotels will have speaker tracks made available to the in-house "cable" channels like other hotels have allowed?

            From DT: (thread discussion for 2 posts being quoted)

            https://forum.defcon.org/forum/defco...amp;viewfull=1

            Originally posted by Dark Tangent View Post
            [chop]
            - Yes, if possible we'd like to have a speaking side and an events side. It will cut down on staff burn out from having to double their walking distances, it will cut costs by not having to pay to flip rooms for events in the evening and flip back for seating in the day, and will help keep the contests energy in one area instead of spread out.
            [chop]
            Then later in the same thread

            Originally posted by Dark Tangent View Post
            [chop]
            Because of that Paris seems the natural choice for speaking tracks.
            With the above in-mind, consider this: (Twitter users asked if video of speakers will be available from Bally's rooms in addition to Paris room?)
            https://twitter.com/_defcon_/status/499798165126914049

            Originally posted by _defcon_On_twitter
            We are working with engineering to answer questions like that.

            Network broadcasting, or multicasting might be options to make video of speaker tracks available to attendees staying in other hotels. My opinion? This is very unlikely this year.
            Last edited by TheCotMan; January 26, 2015, 21:43.

            Comment


            • #7
              Originally posted by USSJoin View Post
              There's a few concerns I have with this project.

              1) Broadcasting something powerful enough to punch through walls even of the convention center is going to be difficult...
              Well, a potential alternative is to set up a bunch of low-power transmitters. DVB-T is designed to allow for Single Frequency Network operation where you can have several overlapping transmitters on the same frequency without interfering with each other. Of course, this would dramatically increase the complexity of generating a signal, but if the walls are fairly impenetrable, perhaps they don't need to be synced.

              For hotel rooms, perhaps small, low-power transmitters with line-of-sight to rooms would work? Of course you'd need several transmitters, and some way to get the content to those transmitters. And who knows what the window tinting does...

              Originally posted by USSJoin View Post
              2) ... So by my reading, this is absolutely one-way, and is absolutely a broadcast---and both are prohibited for what you're trying to do.
              I seem to remember reading something arguing that ATV transmissions aren't broadcasts because you need specialized equipment and/or knowledge to receive them--the general public can't readily receive them like they do with other TV channels. One way transmissions are also authorized for transmitting "information bulletins", which are defined as "A message directed only to amateur operators consisting solely of subject matter of direct interest to the amateur service." This would be a big stretch. (Maybe only talks about RF/software defined radio/etc?)

              Originally posted by USSJoin View Post
              3) While you could in theory apply for STA, that's a big ask for the FCC; STAs are easy to grant for things like ToorCamp's ShadyTel and Burning Man, because *nobody is there*. In the middle of Las Vegas, that's much harder.
              The reason I brought up STAs is that the FCC's amateur radio FAQ specifically mentions them as a way to seek a waiver from the regular Part 97 rules. Shadytel's STA sought permission to operate on spectrum licensed to someone else, whereas this STA might just seek a temporary waiver of the usual "no broadcasting" rules. I have no idea how open the FCC would be to this. It might help to know how much use the ATV parts of the voluntary ham band plan get.

              BUT!

              I do have another idea: TV whitespaces. Part 15(H) is new and deals with "television band devices" that either query a database or use spectrum sensing to operate unlicensed on vacant TV channels. Apparently fixed TVBDs can transmit up to one watt, which might work well with the "many low-power line-of-sight transmitters" plan. A *very* quick skim of the TVBD regulations didn't seem to indicate that you had to use devices that were specifically approved by the FCC for TVBD operation, but I could be wrong on that. But perhaps even if you do, an STA could be used to get a waiver for that requirement?

              Originally posted by USSJoin View Post
              4) Even if you had approval, weren't breaking ham rules, and could buy enough equipment to broadcast strongly enough to be heard---very, very few people could pick you up, with the right combination of hardware and software, and knowledge to actually do it.
              I think far more people could pick it up than you might imagine. Anyone with an rtl-sdr dongle, for example, could receive it. Drivers are built in to Linux, and VLC (and friends) seem to natively support DVB. Windows/OSX users can just install whatever software came with their dongle, as that's what they're designed to do. ;)

              But perhaps this is way too ambitious for this year. Perhaps a better plan would be to try some small-scale, regulation-friendly experiments at DEFCON first?

              Comment


              • #8
                unsure if this should go here or in a totally new thread... but does anyone have a master list of the /movies/ that used to be shown on the DCTV network in the past? i feel like a lot of the same flms wound up in rotation year after year. were they sometimes mentioned in the DEFCON program? i can dig through old PDFs, which are archived online, i am sure.

                i'm working on share a list of some particularly good hacker movies for a few friends and that was going to be my starting point.
                "I'll admit I had an OiNK account and frequented it quite often… What made OiNK a great place was that it was like the world's greatest record store… iTunes kind of feels like Sam Goody to me. I don't feel cool when I go there. I'm tired of seeing John Mayer's face pop up. I feel like I'm being hustled when I visit there, and I don't think their product is that great. DRM, low bit rate, etc... OiNK it existed because it filled a void of what people want."
                - Trent Reznor

                Comment


                • #9
                  tl;dr;
                  Yes, in programs early years, but longer lists were on the DCTV website (probably gone now.) Movies were also discussed on the forums. (Check archives.)

                  Originally posted by Deviant Ollam View Post
                  unsure if this should go here or in a totally new thread... but does anyone have a master list of the /movies/ that used to be shown on the DCTV network in the past? i feel like a lot of the same flms wound up in rotation year after year. were they sometimes mentioned in the DEFCON program? i can dig through old PDFs, which are archived online, i am sure.

                  i'm working on share a list of some particularly good hacker movies for a few friends and that was going to be my starting point.
                  At one time, there was a "dctv" website, which was used to accept requests from users for hacker movies. Lists were made, and augmented year after year. There were forum discussions about these too. When we were at the AP, early DCTV (before DCTV was talks) was listed in the program, and one or two years they included an actual schedule.

                  Originally, the movies were just put in a queue, and played back-to-back. (Well, originally, the first instance of any kind of DCTV was probably DEF CON 6? There was a small square space with a TV and a VCR or laser disk or DVD player and a small audience sitting watching WarGames or other things on a TV. It was like a "family room" kind of setting in one of the DEF CON rooms where other stuff was going on, but with movies, on the DEF CON floor.) So, the first "DCTV" to hotel rooms was movies, and movies were played back-to-back. A schedule was provided, but the queue became "stuck" and that broke scheduling and planning. (There was also another channel used for other content, that was not movies. It was weird clips from con, and other places, but was not the source of the "filler.")

                  Later, the providers of DCTV took advice (or solved this on their own) with having movies start on the hour or half hour, and introduced random "filler" to fill the time between one movie and the next. So, if a movie started at 9am and lasted 95 minutes, then 25 minutes of random filler could be queued up until the 120 minute mark at 11am. This is what survived the longest for DCTV format before DCT became known more about speaker tracks being piped to the rooms. (You know about the DC Filler. :-)

                  Comment


                  • #10
                    We are working away at getting video between hotels, so if all goes well we should have DCTV in Paris and Ballys. No idea how many channels at this point, we'll know in a couple weeks after some testing.

                    PGP key: dtangent@defcon.org valid 2020 Jan 15, to 2024 Jan 01 Fingerprint: BC5B CD9A C609 1B6B CD81 9636 D7C6 E96C FE66 156A

                    Comment


                    • #11
                      Who needs over the air for broadcasts? Send it with Ustream or Qik, or even YouTube live, and those of us on the ball probably have a way to go from a microUSB connector to Displayport and we can feed the video tp the hotel TV. Give us a little credit!

                      Comment


                      • #12
                        It would be great to validate the scope of the DCTV coverage in order to make a decision regarding which hotel we would intend to book for DC. This is actually the one thing holding up my booking for a reservation.

                        That being said, it would also be valuable if the feeds were of adequate quality in lighting/gain and audio. I don't want to make any assumptions about the black box, but the output has been poor in the past. Not my intention to offend a volunteer workforce's good efforts, but really wanted to emphasize how nice it would be to be able to be see and hear the tracks from the rooms when unable to attend talks in person, due to a multitude of things DC; capacity, timing, drunk stupor, etc.

                        It did occur to me, and others during chats at last DC, that if a vendor was providing pass-thru feeds to the house, that the quality level and expectation could be set upfront within any agreement or contract. The fact that I've seen videos post con that have appropriate lighting/gain and audio leads me to perceive that the scenes were captured at a production quality level, but pass thru signal quality was not a priority, but rather a minimum of accommodation. The videos, post production, are good. I understand the complexities of attempting to provide that look and feel in RT, but the wideshot and audio quality is there and DC attendees would benefit from getting a higher quality signal in room. Seems like it's an issue of delivery and interfacing with the host infrastructure.



                        If a chicken and a half, can lay an egg and a half, in a day and a half... how long would it take a monkey, with a wooden leg, to kick the seeds out of a dill pickle?

                        Comment


                        • #13
                          Originally posted by goathead View Post
                          It would be great to validate the scope of the DCTV coverage in order to make a decision regarding which hotel we would intend to book for DC. This is actually the one thing holding up my booking for a reservation.
                          I found a recent tweet on new estimate of when information would be available on which hotels would have a DCTV Feed to the hotel rooms:
                          https://forum.defcon.org/forum/defco...015#post220015

                          If you look earlier in that thread, I suggest earlier public discussions or announcements suggests that the speaker tracks will mostly be in Paris Hotel and Casino, and that would suggest Paris hotel rooms as more likely getting DCTV Feeds than Bally's.

                          For the rest of your post? I don't have anything to provide in comment on the rest. It is not my department. Maybe someone else will reply with an answer for you.

                          HTH,
                          -Cot

                          Comment


                          • #14
                            Thanks CotMan, that was what we were figuring in order to best assure access to the DCTV; locating at the source.

                            As far as anyone responding to me, unnecessary to close the loop with me. Just raising some observations/perceptions/points in case they have not been considered yet.

                            Thanks sir.
                            If a chicken and a half, can lay an egg and a half, in a day and a half... how long would it take a monkey, with a wooden leg, to kick the seeds out of a dill pickle?

                            Comment


                            • #15
                              Ideally I'd love to see DCTV piped via the interwebs vs broadcast into the rooms of either/both hotels. I think this would be far better for people around the conference (ie. not in their room) to catch some talks. Last year between the villages, and gooning I seen 10 minutes of 3 talks (maybe).


                              If that can't/won't be done rather than attempt a side by side or PIP speaker vs slides view I'd rather see 2 channels piped to the room per talk. 1 channel for the speaker/panel/stage shot and another channel (with an identical/synced audio stream) tide into the projector/slides. This way for ex. you could watch track 1 speaker on ch.50 or track 1 slides on ch.51 with the same audio on either.

                              2 cents

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