Posts: 2
Joined: Fri Dec 18, 2020 4:04 pm

Wireless HDMI streaming

Fri Dec 18, 2020 4:26 pm

I'm looking to stream an HDMI signal wirelessly between two Pis, using a TC358743 on the camera port of the input Pi and playing video from the HDMI port of the output Pi. I'm quite new to Raspberry Pi so bear with me.

Here are some of my design parameters:
- Currently the video source will just be a laptop. The input stream will be 720p.
- Audio streaming is not required.
- While 60fps is preferable, 30fps is acceptable.
- A little bit of latency (<1s) is acceptable.
- I will have a dedicated WiFi network to support the video streaming.

I've tried this tutorial (https://dantheiotman.com/2017/08/23/usi ... streaming/) which uses raspivid streaming over netcat to mplayer on the receiver. It seems to work very well with the actual Camera V2 module, but there is almost 10 seconds of latency with an HDMI input. This seems to be due to the processor taking a long time to decode the HDMI-CSI2 signals. However, the HDMI signal plays natively with excellent resolution and almost no latency.

I'm not sure where to go from here. Currently I'm attempting to replace raspivid with V4L2, but I can't figure out how to pipe that into netcat and I'm not sure if it will have the same latency issues when streaming.

Where should I go from here? Any other methods I can try?

(I understand there are commercial wireless HDMI products out there but I'd like to eventually expand this project to include some custom features on the Pis.)

Posts: 2
Joined: Fri Dec 18, 2020 4:04 pm

Re: Wireless HDMI streaming

Mon Jan 04, 2021 8:33 pm


So far the furthest I've gotten is to use v4l2 to write an EDID file to the TC358743 on the transmitter, then use yavta to pipe the HDMI input into netcat. The receiver would then use netcat to receive the data and play it using mplayer. This results in a latency of 3-5 seconds, but the framerate on the output is quite bad and flickery.

Here are the commands I used:

Code: Select all

v4l2-ctl --set-edid=file=720P30EDID.txt --fix-edid-checksums 
v4l2-ctl --query-dv-timings
v4l2-ctl --set-dv-bt-timings query
cd yavta
./yavta -c -f UYVY -n 3 --encode-to=- -m -T /dev/video0  | nc 5000

netcat -l -p 5000 | mplayer -fs -fps 60 -cache 2048 -cache-min 1 -

Since the HDMI stream plays natively on the transmitter with excellent resolution and very low latency, I've looked at possibly getting the transmitter to share its screen/desktop remotely. I've managed to get this working with VNC, the output video has decent image quality but terrible framerate (maybe 10fps max). Is there a more efficient way of doing this?

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Posts: 11
Joined: Sat Jan 09, 2021 4:35 pm

Re: Wireless HDMI streaming

Tue Jan 12, 2021 4:52 pm


I hope this gets continued, I have always been interested in this topic but have not found anything quiet fulfilling the task (other than a cable)...

So please keep up the work!

"Dieses Internet, das wird sich nicht durchsetzen."

Zitat: Erich Honecker

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