Video Support

[mrtnkhl]

There is currently no video support planned until bus protocol reverse engineering is done and interfacing with the digital bus is fully working. Creating this Issue as a placeholder for possible future work and to inform others who might be looking for video support.

Details concerning possible Audio support are tracked in Issue https://github.com/gdoor-org/gdoor/issues/20.

Per @DaSchaef there is sufficient evidence to assume that video is transmitted in analog just like the audio part of the communication with the (door) station in a resolution of roughly 320x240 pixels (or respective lines) per @jschroeter . It is assumed that an ADC would be needed to convert the analog signals to digital for the ESP32 and then send them via SIP/RTSP/RTP to a destination on the network. Issues outlined in https://github.com/gdoor-org/gdoor/issues/20 apply, in addition to those the extra bandwidth needed to digitize the video signal from the wire is going to be of concern.

[mrtnkhl]

See this thread for a similar discussion for a Comelit system: https://github.com/Elektroarzt/simplebus2-mqtt-bridge/issues/3

[mrtnkhl]

https://www.eevblog.com/forum/projects/ic-for-capturing-composite-video-screenshot/

[mrtnkhl]

https://github.com/wooky/esp32-analog-video-over-wifi

https://github.com/11tools/esp32cvbscam

[jschroeter]

I can confirm that the resolution is 320 × 240 since the images saved on the SD card of the indoor station do have that resolution. They are saved as BMP files but I guess this is irrelevant.

[jschroeter]

A bit off topic, but while I was setting up mobile notifications when someone hits our door bell I noticed that the Home Assistant mobile apps supports attaching a camera image/stream to the notification: https://companion.home-assistant.io/docs/notifications/notification-attachments#automatic-snapshots

I initially thought I don't need this, but of course, once I got the adapter running and read this, I immediately thought: that would be cool :-)

[DaSchaef]

https://github.com/antmicro/cvbs-mipi-bridge https://github.com/o-murphy/cvbs2rpi

[DaSchaef]

For buffering video https://jlcpcb.com/partdetail/TexasInstruments-THS7374IPWR/C2652746

[DaSchaef]

I have a question to the owners of video installations:

Is the video parallel to the audio conversation? If yes, the video signal may be modulated and no simple "cinch video", and we would need to find out the modulation scheme.

[mrtnkhl]

Video and audio are transmitted in parallel. Not sure if audio is duplex but I think it is.

[DaSchaef]

Hmm, we need someone with a video installation and at 40MHz bandwidth (better 100Mhz) oscilloscope. We need to record start of video, to identify the video modulation/signal scheme.

I'm not 100% familar with analog video, but from what I understand: the standard CVBS goes down in the spectrum, overlapping with the audio range. So I would assume that the video may be FM (or even AM, but I don't think so) modulated to shift it to higher frequencies.

Or audio / video is interleaved? Don't know if such a thing could work

[mrtnkhl]

Any recommendations for an affordable USB oscilloscope that would satisfy those requirements? My GIRA system has video.

[DaSchaef]

I had a quick glance at Video Bus signals.

Sadly they seem to be modulated, over 100 MHz? I had a bit of trouble with my cheap 100MHz oscilloscope. It may be over 100Mhz or the cheap scope was crap :wink:

I'll try a SDR solution next time, so that we first can get a feeling about the needed carrier frequency, and be sure what expected range to measure and that we use the right measurement setup.

As the Modulation may be over 100 MHz it may indicate that standard analog TV modulation is used?? From Wikipedia: