Transmitting HD Video From A Raspberry Pi

It’s been a few years since the RTL-SDR TV Tuner dongle blew up the world of amateur radio; it’s a simple device that listens in on digital television frequencies, but it’s one of those tools that’s just capable enough to have a lot of fun. Now, we have a transmitting dongle. It’s only being used to transmit live HDTV from a Pi, but that in itself is very interesting and opens up a lot of possible builds.

The key piece of hardware for this build is a UT-100C DVB-T modulator. It’s a $169 USB dongle capable of transmitting between 1200-1350 MHz, and with a special edition of OpenCaster it’s possible to transmit over-the-air TV. There’s no amplifier, so you won’t be sending TV very far, but it does work.

On the Raspberry Pi side of the build, the standard camera captures H.264 video with raspivid, which is converted to a DVB compliant stream using ffmpeg. These are well-worn bits of software in the Raspberry Pi world, and OpenCaster takes care of the rest.

While this seems like the perfect solution to completely overbuilt quadcopters, keep in mind transmitting on the 23cm band does require a license. Transmitting in the UHF TV bands is a bad idea.

30 thoughts on “Transmitting HD Video From A Raspberry Pi

    1. My first thought as well, on the other hand they aren’t used for much else these days, probably got them from the same place that sells 50 ohm BNC tees by the pound! I remember these connectors from semi-pro video recorders from the 70’s – 1/2″ open reel black and white only and they weighed 30 pounds.

          1. He did label the input DC IN on the box, hopefully labeled the PSU DC OUT as well? I am in favor of standardized connectors but if you consider that the RCA connector used for audio was designed as a 75 ohm RF connector originally and all of the amplifiers with 1/4″ speaker outs which can be plugged in to microphone/instrument inputs with disastrous results some degree of common sense hopefully should be involved as well.

      1. Come to think of it… some satellite dish motors, and certainly the power for the LNB, use DC sent along satellite cables with plugs quite a lot like that. Dunno if identical. And DC is toward the lower end of the RF spectrum.

    2. The DC plug, I dont know about. However the 3.5mm jack for data has been used before by Apple. They used it on the ipod shuffle. The audio jack served to charge, transmit data and playback audio. It used a four layer style jack.

      1. It seems to me that I remember there once being a lot of devices out there that did TTL serial through 3.5m jacks. That would be back before USB chips were so cheap and plentiful.

  1. hang on, I’m tuning my power supply so that its SWR is below 1.2


    yeah, pl259 for power-in. that’s a new one for me! at least he didn’t use the shorting TRS style audio jacks (remember audio alchemy and how badly they executed the dc power brick plugs? trs connectors for power. and they thought of themselves as professionals, too. you don’t have to be an amateur to make bone-headed connector decisions; ‘pro’ companies do that, too (boggle!)

    1. If they used the male side of a TRS for power that’s outright retarded, that will short out on just about anything you lay it across, heck even if it’s a female side TRS involves contacts sliding past one another, it’s for line level applications only..

  2. To be accurate, Open Caster does the data encoding, but does not do any audio/video encoding. He’s using ffmpeg to encode the a/v into the .ts (transport stream) which then gets muxed with the Open Caster data and is then sent out as rf.

    1. With an H.264 encode in the signal chain? I’d be amazed if the latency was less than one second. Four seconds is more likely. Though with some hacking into hidden settings, i bet latency could get below 300ms.

        1. Oh, forgot to mention – not completely useless, if you are using a better camera (or a DLSR), you could have a nice preview (check focus etc…) once in some kind of autopilot mode…

      1. Actually the encoding isn’t particularly bad; that’s all in hardware on the Pi side. The big culprit is usually buffering on the decoder side. I wrote the esvideorpi2pes tool to wrap the rpi camera stream into PES so the stream creation could be done completely in OpenCaster without pulling in ffmpeg, and latency didn’t change.

        Some asshole wrote a DVB-T decoder that got sub-0.3s latency, made one post about it without links on the rpi forums, then vanished forever. Urge to kill, rising…

  3. I’m not sure a $169 dongle is really in the same class as the RTL-SDR. I suspect that most hobbyists wouldn’t really hesitate or think tiwce about purchasing an RTL-SDR stick if they thought they might want one. A $169 purchase though.. for a mere hobby I would think that would be a once in a several month period kind of purchase. It’s something that one would have to weigh against other tools and devices that one might also desire and only chose one.

    Of course… people’s means do vary. I’m sure that some of us can go out and buy these things like candy. (care to buy me one?) I’m also sure that some of us even struggle to buy the RTL-SDR. I hope that more of the latter are pre-employment kids rather than adults trying to support families. Sadly I’m sure there are some of both.

    I know I have seen HF SDR transcievers in the $80-90 range for years not that you could do real time video through them. That’s closer to being comparable but still not there. It would be great if some day there really is a transmitter that is comparable to the RTL-SDR! I don’t think that this is it.

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