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arfvcr

A friend from the Makers of Murcia hackerspace brought a few 80s tube TV cameras to a retro meetup, and they were free to take. I took one such SONY Trinicon HVC-4000P, an awesome camera that was released in the early 80s. At that time, camcorders didn't exist, they were television cameras because there weren't small enough tape mechanisms to be integrated in. They required heavy external battery powered VCRs like the Sony SL-F1, that you would hang off your shoulder, which we did not have. So I thought I'd build a digital knockoff.

The thing is basically a battery powered video capture box, a little computer with a composite capture card attached. I chose to base it on a Raspberry Pi 4B because it has to be fast enough to encode video at real time; and for the capture card I had a *forgot* USB card, that exposes a raw yuv422 stream thanks to the video4linux2 driver. Interfacing with the camera, the same friend gave me the hard to find matching female connector that I could just mount to a chassis. Finally for power, because I am a cheap and simple person, I went with a 7Ah lead acid battery, which was very controversial in the hackerspace telegram channel :)

So, power comes in from the battery or a barrel jack in the front panel, and comes to a general power switch. That then goes to a 12-to-5V buck converter for the raspi and to another toggle switch for the camera. The front panel also has a volt meter to check battery charge, power and status LEDs, the rec/review switch and of course, the proprietary SONY connector for the camera.

The tethering cable has AV in and out, because it can also review recorded footage; and some control signals as well: recording start/stop (from camera), rec/review (from camera), tally signal in (from VCR: switches the viewfinder and monitor headphone jack to AV in). Now, slight problem. I don't know how the signaling is supposed to work. start/stop and rec/review aren't simple HIGH/LOW signals, they have no voltage when hitting the reflected buttons. The camera also doesn't respond to a LOW or HIGH on the tally sig in, 5 nor 12V, maybe open drain(?). I should review the public schematics for the thing and figure it out. Also, the audio out appears to be quiet.

Software wise, I installed Debian 12 for ARM64, and then found that I needed a feature for power debugging, so I had to install the downstream rasperry-pi kernel and userspace software. I found that the hardware encoder never worked at all with any OS or ffmpeg version so it mattered not, thats why I needed a fast raspi, for RT libx264. Of couse as mentioned, ffmpeg was chosen by default for video capture and encoding. I love ffmpeg. Thanks Fabrice Bellard. ffmpeg is love, ffmpeg is life.

Because this is a headless device and I shouldn't need a console to hit record (although the raspi creates a WiFi network to ssh into), I had to write some software to trigger ffmpeg; so I wrote a daemon in C that reads a GPIO pins from a record front panel toggle switch or the camera (start/stop signal - explained before) to start and stop the capture, and a record status LED that turns on only if ffmpeg has open the capture card. All of this is GPL available at github.