Reverse Engineering an HDMI Extender

reverse-engineer-hdmi-extender

There’s a number of devices out there that extend HDMI over IP. You connect a video source to the transmitter, a display to the receiver, and link the two with a CAT5/5e/6 cable. These cables are much cheaper than HDMI cables, and can run longer distances.

[Daniel] didn’t care about extending HDMI, instead he wanted a low cost HDMI input for his PC. Capture cards are a bit expensive, so he decided to reverse engineer an IP HDMI extender.

After connecting a DVD player and TV, he fired up Wireshark and started sniffing the packets. The device was using IP multicast on two ports. One of these ports had a high bitrate, and contained JPEG headers. It looked like the video stream was raw MJPEG data.

The next step was to write a listener that could sniff the packets and spit the data into a JPEG file. After dealing with some quirks, JPEG images could be saved from the remote device. Some more code was needed to have the computer initiate the streaming, and to extract audio from the second port.

In the end, video capture with the low cost device was possible. [Daniel] also provided a bonus teardown of the device in his writeup.

Capturing video with an Arduino

[Carlos Agell] sent in a tip where he captured images from an analog camera with an Arduino.

We’ve seen a few AVR/Arduino hacks that generate video, although overclocking is necessary if you want to do anything beyond a Breakout clone. [Carlos]‘ hack bucks that trend and now he can capture video with an Arduino.

The project captures individual frames from NTSC video at a resolution of 128×96. Although the Arduino isn’t powerful enough for real-time capture, [Carlos] managed this by capturing only thresholds and sending them over to a computer running a program coded in LabVIEW. The PC program reassembles the images of the thresholds and produces a tiny image in 3-bit grayscale.

[Carlos] used the Video Experimenter shield which is impressive in it’s own right. The Video Experimenter is able to do object tracking and edge detection, so we’re wondering when we’ll see robots with computer vision running off an Arduino. Check out a demo of the nootropic design video experimenter shield after the break.

UPDATE: Carlos wrote a sketch in Processing that does the same thing as his LabVIEW program.

[Read more...]

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