[HN Gopher] Analog TV Station on ESP8266
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Analog TV Station on ESP8266
Author : dvfjsdhgfv
Score : 333 points
Date : 2020-12-07 10:17 UTC (12 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| nallic wrote:
| cnlohr does a lot of cool RF stuff - he has a Youtube channel
| well worth a follow!
| ParanoidShroom wrote:
| Highly recommend the channel. His journey of reversing the Valve
| Lighthouse is also fun.
| jiofih wrote:
| Looks very cool, but it's been almost a decade since I've last
| had an analog TV. Do people still have them around?
| pkamb wrote:
| https://old.reddit.com/r/crtgaming/
| Piskvorrr wrote:
| Even new systems have them, probably because the radio on the
| chip is something SDR-ish; also, there is equipment that still
| transmits analog signal, just not over the air (think CCTV et
| al.).
|
| So yeah, the receivers are still shipped, just ~nobody tunes
| into their ranges anymore.
| jiofih wrote:
| They don't come with antennas though (and houses don't have
| them anymore), so the majority of devices are unable to tune
| to anything. In my country everything has moved to digital
| and the spectrum sold for mobile use.
| xgulfie wrote:
| Indoor antennas can be bought for like $15 here in the US
| anthk wrote:
| The US is sparse. In Europe you are like in a tin of
| sardines and most people live in flats. I can't get dvbt
| over the air where I live because of:
|
| 1) Everyone got fiber tv so the old communitary antenna
| has been taken down from the roof
|
| 2) My building is surrounded by taller ones blocking the
| signal for a tiny 40DB indoors antenna
| Piskvorrr wrote:
| I'm receiving DVB-T2 off the same wiring and antenna that
| was used for DVB-T, and analog before that. _shrug_
| Different part of the world, perhaps?
|
| https://en.wikipedia.org/wiki/Belling-Lee_connector
| toast0 wrote:
| New TVs still have analog tv decoding from what I've seen. It's
| the same frequencies as digital tv, and if they have a
| composite video input, it's the same process, so not very much
| extra to support it.
|
| There may only be a few OTA broadcasters left on analog in the
| US, but I don't know how far the digital transition went in
| developing markets. I'd bet there's some rural cable systems
| still running analog as well.
| Abishek_Muthian wrote:
| Analog TVs have been indispensable for the marginalised, under-
| represented children living in remote areas to receive
| education during this pandemic lockdown.
|
| As the availability of Internet, Devices capable of receiving
| online courses has been taken for granted, many who are not
| privileged not only missed education for several months now but
| also lost communication with their schools.
|
| I've been thinking about inexpensive compute capable device
| capable of receiving analog TV via SDR and also communication
| through LoRAWAN[1] to address this. Now I'll also explore
| ESP8266's ability to receive analog TV signals.
|
| [1]https://needgap.com/problems/149-remote-education-for-
| underp... (Disclaimer: it's my problem validation platform).
| kalleboo wrote:
| The navigation in the in-laws car has an analog TV tuner (along
| with a minidisc player), I could actually use this
| hideo wrote:
| For a moment I thought he was running an analog TV _receiver_ on
| ESP8266, but this is so much cooler!
|
| For anyone looking for the TL;DR:
|
| > This is basically a 1-bit dithering DAC, operating at a
| frequency below the nyquist, trying to encode luma and color at
| the same time
| ananonymoususer wrote:
| Great work! This reminds me of a book I read over 40 years ago:
| https://www.amazon.com/Cheap-Video-Cookbook-Donald-Lancaster...
|
| Apparently Don has made the above book available on his site:
| https://www.tinaja.com/ebooks/cvcb1.pdf
| josu wrote:
| Would this work on a Raspberry Pi? It also has a GPIO3 interface.
|
| https://pinout.xyz/pinout/pin5_gpio3
| miahi wrote:
| GPIO 3 means "The third pin with General Purpose I/O
| functionality" - a generic pin that can be used for custom
| protocols. In the case of ESP8266, the pin is also used for I2S
| SD (data pin of the I2S bus), and this is what is actually
| used, because the I2S implementation in ESP8266 can work at
| 80MHz.
|
| I don't seem to find the specifications of the I2S in Raspberry
| Pis, all I can find is in the range of kHz. So probably it
| cannot be done.
| th0ma5 wrote:
| Not sure about frequencies nor NTSC but I've transmitted from
| Ohio to New Zealand with no amplifier (once) using WSPRRYPI and
| there is also https://github.com/F5OEO/rpitx
| lqet wrote:
| Ha, I will give this a try. My current setup: I have a Browni
| portable TV [0] from the 1960ies in my home office (20 EUR on
| Ebay 13 years ago, still working perfectly), hooked on a
| composite to coaxial adapter, hooked on a HDMI to composite
| adapter, hooked on an old Chromecast. Even the audio works
| perfectly. But using the build-in antenna of the Browni would be
| even better.
|
| [0]
| https://www.radiomuseum.org/r/cbc_browni_transistor_tv_space...
| VBprogrammer wrote:
| The standard ham radio cry of "think of the spectrum" applies
| here. It's great as a demo but please don't intend to use it
| for anything serious, this is likely outputting harmonics into
| areas of the RF spectrum that people care about.
| willis936 wrote:
| Slightly related anecdote:
|
| I have a raspi zero whose only job is to set its clock
| frequency to 104.1 MHz and modulate it with Daft Punk's
| Daftendirekt every morning for a clock radio that I picked
| out of the trash.
|
| Well below the 5 mW power limit but it comes through clear in
| the same room.
|
| Edit: for the first week I was broadcasting over the local
| NPR station. There were likely people on commutes nearby
| getting interference from me, so I switched to dead space.
| lqet wrote:
| I am hesitating to ask, but would you mind sharing the
| code?
| willis936 wrote:
| I wrote nothing. Be warned: setting the transmit
| frequency below 100 MHz will result in the raspi locking
| up.
|
| https://github.com/markondej/fm_transmitter
| jsight wrote:
| I was wondering about this with the OP. I wonder what the
| power level is?
| jacobush wrote:
| Probably not at a power level which really matters?
| anthk wrote:
| Radio waves travel for long. I remember getting local AM
| radio tunes 100 km away from the border of my province
| where in theory the radio is being set for.
| bayindirh wrote:
| Waves can propagate in very unpredictable ways and create
| unintended consequences. It's better be safe than sorry is
| very applicable here.
|
| Even a ~1W radio can go a long way, even in a city. So,
| yes, _think of the spectrum_.
| jacquesm wrote:
| 1W is a fairly massive amount of power though, a typical
| small DIY project will output a couple of mW. So unless
| you very explicitly start amplifying it after your
| oscillator there most likely will not be too much power
| radiating out unless you hook it up to another stage or a
| directed antenna (which gives you a passive way of
| boosting the radiated power by concentrating the output
| on a more narrow angle).
| bayindirh wrote:
| Yep, you're right. However, since Walkie-Talkies' power
| is around that level, I thought it'd be a good example to
| build upon.
|
| Regardless of the power level, thinking about spectrum
| and trying not to create harmful interference is
| important IMHO. I live in a place where listening FM in
| stereo mode is impossible due to interference and radio
| transmissions around me. Even Wi-Fi cannot penetrate
| beyond next room.
|
| We've looked how spectrum looked here with a listen-only
| SDR. It wasn't pretty. My friends' exact words were
| "Dude, that's not what I see at home. This is some
| serious traffic."
| Uberphallus wrote:
| WSPR managed to transmit data at 150,000 Km/W [0], so yeah,
| unfiltered transmissions are a pain in the ass for the rest
| no matter the power.
|
| http://wsprnet.org/drupal/node/5089
| jameshart wrote:
| Outputting a TV signal isn't inherently a problem, surely?
| Every VCR and 1980s home computer has a circuit that does the
| same thing. Would only be an issue if you run it through an
| amp and antenna, rather than just running a wire to a TV,
| right?
| ddingus wrote:
| Those sources are likely shielded and clean.
|
| A transmitter like this will radiate harmonics, and that's
| the major concern. It is not just a TV signal.
|
| All that said, this is nice work. Analog signals are a lot
| of fun.
|
| NTSC going away makes me sad. I have abused it to great
| results many times over the years.
| jameshart wrote:
| But doesn't that concern about unshielded dirty signals
| apply to basically any use of a GPIO pin on a dev board?
| ddingus wrote:
| Yes and no. Depends on the frequencies, whether the pin
| is driving a load, and intended to radiate.
| verytrivial wrote:
| This guy is great -- the livestream VR coding stuff is pure
| hacking fun, and it's all so painfully wholesome. Highly
| recommended.
| cnlohr wrote:
| This comment made my day.
| CraigJPerry wrote:
| https://m.youtube.com/c/CNLohr/videos
| ducktective wrote:
| Similar project with ESP32 for Composite Video [by bitluni]:
| https://www.youtube.com/watch?v=5t1_XNc3vNw
| CommanderData wrote:
| I wonder if this hardware can be used to exploit know DVB
| vulnerabilities.
| est31 wrote:
| Wow this is hacking in the most literal sense: using something in
| a way it was not designed for. Even avoiding nyquist problems by
| abusing some mirror effects if I understood that correctly.
| moonbug wrote:
| NTSC, not PAL or SECAM.
| peterburkimsher wrote:
| Could a similar thing be done for FM transmitting? I've seen it
| be possible on the RPi GPIO, just not the ESP yet:
|
| https://github.com/miegl/PiFmAdv
| timonoko wrote:
| I suggest doing something useful: Tiny emergency transmitter at
| Marine VHF16. This is voice-only channel, so maybe it should just
| repeat prerecorded message at every hour. Rescue services can
| pinpoint the source, so nothing fancy needed. Activating this
| transmitter would be illegal, but me myself prefer life in prison
| to death.
| drewbug wrote:
| 47 CFR SS 97.403: Safety of life and protection of property.
|
| > No provision of these rules prevents the use by an amateur
| station of any means of radiocommunication at its disposal to
| provide essential communication needs in connection with the
| immediate safety of human life and immediate protection of
| property when normal communication systems are not available.
| timonoko wrote:
| I think some guy in Oregon ended in prison because he
| activated the EPIRB dozens of times -- for broken fingernails
| and other such emergencies.
| tzs wrote:
| I'm sure there must be something that covers it, but I'm not
| sure it that.
|
| That seems to only apply to amateur stations, which 47 CFR
| defines as stations in an amateur service. I.e., ham radio
| stations.
|
| I've got a ham radio license, so it would cover me if I
| transmitted outside of the ham bands, or exceeded power
| limits, or used an unauthorized modulation method to try to
| help save lives and protect property, but for someone without
| a ham license I think we'd have to look elsewhere for legal
| cover.
| [deleted]
| jcrawfordor wrote:
| I can't really imagine this having any advantages over a PLB
| which are fairly inexpensive and already built to be waterproof
| and impact resistant. PLBs are monitored from orbit by COSPAS-
| SARSAT and modern versions have active location reporting which
| _nearly_ guarantees fairly rapid reception and location fix.
| Satellite monitoring of aviation guard (121.5) has been
| officially ended by COSPAS-SARSAT and I 'm not sure it ever
| monitored marine radio. Radiolocation of VHF 16 can be done but
| is going to be substantially more time consuming and less
| accurate than a COSPAS-SARSAT report - accuracy requires having
| nearby vessels properly equipped or sending an aircraft.
| timonoko wrote:
| They are not inexpensive. In Finland you need a Radio
| Operator Licence and pay some 20EUR annually and also you
| have to pay for reprogramming the special "National ID". And
| thus this mostly useless device costs 400EUR:
| https://www.marnela.com/product/1304-01261
|
| Some 40 years ago I made 2 Mhz emergency Morse transmitter
| from RCA Cosmac, because I planned to spend a summer on
| Antarctis. It worked quite well with long ass wire antenna.
| But they do not monitor that frequency anymore and nobody
| understands morse.
| robterrell wrote:
| Similarly, a favorite ESP8266 hack of mine is this Apple I
| emulator that includes wireless PAL output:
|
| https://github.com/hrvach/espple
| ducktective wrote:
| Thanks for the link! Interesting project. Is there a source for
| the emulator part? There are only binaries here:
| https://github.com/hrvach/espple/tree/master/software
| hrvach wrote:
| Yes, entire project is open source - check
| https://github.com/hrvach/espple/tree/master/user
| jacquesm wrote:
| How neat, actually hacker news :) Definitely upvoted.
| OldHand2018 wrote:
| Is it possible to use a wire connected to a gpio pin as a
| receiving antenna?
| rashkov wrote:
| You all might also enjoy analog TV encoding/decoding in your
| browser: https://substack.net/tv
|
| based on these repositories: https://github.com/substack/glsl-
| ntsc-video - modulate and demodulate an ntsc video signal in a
| shader
|
| https://github.com/substack/ntsc-video-simulator - real-time ntsc
| television simulator
|
| https://github.com/substack/analog-tv-simulation - the demo
| itself
| lxe wrote:
| Substack! Now that's a name I haven't heard in a long time.
| thomond wrote:
| So when he says "channel 3", what is meant by this? Is it a
| particular frequency? (I'm not an American)
| ThePowerOfFuet wrote:
| Yes, the analog channels each had specific fixed frequencies.
| iso1631 wrote:
| I would guess it's VHF channel 3, which is from 60-66MHz, with
| the NTSC video carrier (Luma) on 61.25MHz, audio on 65.75MHz,
| and the Chroma carrier some nasty number about 3.58MHz above
| the Luma carrier.
|
| In my country, VHF TV transmissions started going out in the
| 60s when colour came in, and were fully turned off in the 80s.
|
| Modern DTV runs over UHF channels (replacing the previous
| analog transmissions between 2009 and 2012)
| ficklepickle wrote:
| Channel 3 (or 4) was also commonly the channel used by
| various peripherals like VCRs and composite adapters.
|
| I have fond memories of tuning the TV to channel 3 to play
| Nintendo as a kid. This would make for an interesting retro
| gaming experience.
|
| I wonder if it is easily adapted to use coax cable instead of
| an antenna.
| bonzini wrote:
| Europe used UHF channel 36 instead! Memories :)
| alexisread wrote:
| I don't know much about transmission, but would a modified
| version of this work for PAL TVs? I guess you'd modify the
| frequency but what to?
| iso1631 wrote:
| PAL generally runs on an 8MHz channel, and encodes colour
| in an entirely different way (each alternate line is
| reversed, meaning that small errors cancel out - where in
| NTSC you had a "Tint" control to adjust to any errors).
| ddingus wrote:
| PAL also requires considerably more accurate and
| consistent color information. NTSC displays will usually
| take almost anything close and display it.
|
| See the Apple 2 video circuit for a great example of
| that.
| iso1631 wrote:
| Hence "Never Twice the Same Colour"
| ddingus wrote:
| With high persistence phosphors, PAL is nice. The higher
| frequency color makes a notable difference.
|
| 50hz was often just a bit slow for me. PAL 60 is where it
| was truly at, IMHO.
|
| Both formats have nice abuse potential, and exploiting it
| on early computers, and later on, microcontrollers, is a
| lot of fun.
| ggm wrote:
| "turn a DEC 10 into an fm transmitter" to play digital music
| (which was on a DECUS tape IIRC)
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(page generated 2020-12-07 23:00 UTC)