Goal: Moving away from proprietary/royalty video framing formats
JC
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My knowledge in this topic is limited, but I understand that HDMI is a proprietary video format that involves a small royalty for every unit that includes it.
Source: https://en.wikipedia.org/wiki/HDMI#HDMI_Fee_Structure
It would seem that while DisplayPort is not "completely open," it is a step in the direction of freedom. Right? Well, I contacted DisplayPort to see what restrictions are involved. The following is the complete conversation thus far:
ME:
"I apologize in advance for what may seem an ill-informed message as I'm still learning, but I greatly appreciate any feedback/education you can provide. I have recently become a full-time advocate for open-source hardware/software and am conducting research on the next steps in constructing a "more open-source" computing platform. In a nutshell, I am leading a development group to work toward a RISC-V powered computing platform and attempting to strip as much proprietary/patented/licensed/etc content from it as possible while still being functional/marketable.
I understand that most boards which claim to be "open source" still utilize an HDMI connector and have an HDMI framer IC on the PCB. Graphics drivers aside (as that's another story altogether), I am highly curious what IP restrictions, if any, will apply to leveraging DisplayPort over USB-C. I feel it is potentially a fantastic way to reduce the physical footprint of the connector, reduce framing complexity (maybe?), offer more transparency and (less? no?) additional licensing cost to manufacture."
DISPLAYPORT:
"AMD, Nvidia and Intel all switched to DisplayPort as the native graphics standard some years ago. For the many products that have HDMI today, a converter is used internally. Often this a device from Synaptics that is DP In and up to two DP, one HDMI and one VGA out so very easy to use.
Regarding DisplayPort over USB-C connector, VESA offers the DisplayPort Alternate Mode over USB-C standard. The USB standard describes how to enter and exit (any) alt mode and the VESA standard describes the details for DisplayPort. An HDMI Alt Mode standard has been published, but all of the USB-C adapters in the market are USB-C to DP with a DP-HDMI adapter inside.
DisplayPort and DP Alt Mode can be implemented royalty-free. To get the current versions of the standards, you must be a VESA member. Contact [email protected] for details."
lkcl Sat 5 May 2018 10:33AM
i'm beginning to investigate this as i actually have to get it done (for the Libre RISC-V SoC). the strategy that the Libre RISC-V SoC is going with is to use Richard Herveille's excellent vga_lcd hard macro (see opencores.org) and to use external converter ICs such as the SSD2828 from solomon for MIPI, SN75LVDS83b for LVDS, and offerings from Chrontel for other formats including HDMI or from TI such as the TFP410a.
this strategy allows the licensing problems to be completely side-stepped, as well as sticking to an entirely libre-licensed RTL. the SN75LVDS83b is about $0.75 in volume if you get the NT7181 china-clone pin-compatible knock-off version.
also from talking with another company that actually used vga_lcd i have the full linux kernel source code that they wrote, so there is no major software development cost associated with using it.
Phil H · Sat 5 May 2018 9:59AM
Wow, it seems like implementing a “royalty-free” standard actually costs at least $5,000/year.
One might consider using network based protocols instead:
The nearest thing to a standard is Miracast, which seems to be about as restricted as DP, but there is a free software implementation. I don't particularly like miracast though, because it requires WiFi.