HDMI Capture and Analysis FPGA Project (2015) | Hacker News Reader

HDMI Capture and Analysis FPGA Project (2015)

warmcat.com

56 pointswalterbell10 comments

This may be a long shot, but is there someone here who knows about HDMI video freezing? I'd like to design a freeze button, like in some projectors, as a separate hardware accessory. Plug in HDMI input and output, then press a button to change between pass-through and freezing the last frame.

This is doable with the right hardware. You'd need HDMI decoder and encoders and enough internal or external memory to buffer the resolution you are working with. (1080p = 1920 x 1080 x 3 = 5.9MB) You can probably avoid having to double buffer if it waits for vsync to switch modes.

One potentially helpful piece of out of the box hardware is bunnie's NeTV, which has an fpga in an HDMI path. By default it does overlays on an HDMI signal but with some FPGA rejiggering I suspect doing freeze frames ought to work. At least on non-drm'd HDMI signals.

https://kosagi.com/w/index.php?title=NeTV_Main_Page

The minispartan FPGA devboard has HDMI in- and output and is decently priced. On the other hand, I don't think it is fast enough to process full hd (only hd, so 1280x720).

See http://hamsterworks.co.nz/mediawiki/index.php/FPGA_Projects for many examples (also using different boards).

Edit: Just realized that storing a single frame needs quite some memory. This is something you need to keep in mind. If you use the DDR RAM on the board you'll probably be find, but this is not trivial (even using the tools designed to do this).

Don't you need an Intel-signed pubkey to intercept anything using HDCP? How do you get around that? Or has HDCP been cracked?

Search for HDCP in this thread: https://news.ycombinator.com/item?id=18216910

@walterbell submitted this, so intuition tells me I should be paying attention, but all I read is someone struggling with single-link digital video implementation on a FPGA and a sponsored advertisement for a tool that doesn't quite make sense in context.

I think I may have had one too many drinks tonight. Did I miss something?

HDMI capture on an FPGA board that does not have an HDMI input. Over the six-part series of blog posts, the author explores the 2015 limits of FPGA hardware performance and IP segmentation for HDMI processing around $150 price point, e.g. http://zedboard.org. Other video projects with less connector hacking:

$250 Spartan-6 HDMI Light: https://news.ycombinator.com/item?id=18216910

$350 Numato Opsis Spartan-6 HDMI2USB (2015): https://blog.mithis.net/archives/category/timvideos-us/hdmi2... & https://github.com/timvideos/HDMI2USB-numato-opsis-sample-co...

$500 Artix-7 Digilent Nexys, https://store.digilentinc.com/nexys-video-artix-7-fpga-train...

$900 Zynq MPSoC (Arm Cortex A53 + Xilinx FPGA) with H.264 video encoder, https://www.xilinx.com/products/boards-and-kits/zcu104.html

Author apparently ran into issues while developing hardware with hdmi output, found out that proper logic analyzers capable of wire-speed capture and analysis of non-video-related data (=transmissions during screen blanking time) are expensive and decided to roll with an fpga based solution as well as document it and how HDMI works.

Quite interesting, especially for those of us designing e.g. host boards for RPi Compute Modules.

This is the introduction page, follow the links at the bottom for more, there is a lot of interesting detail including things like writing a kernel driver to interface with the HDMI receiver.

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