HDMI 2.1 & TMDS Crash Course - ENMU EET 457 - Presentation 

One of my worst fears is breaking a pin I soldered onto my board 😭 I'm lucky to be new so it hasn't happened yet.

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Wow. I appreciate that. That is high praise coming from someone already in the industry. I was an early adopter of 4K and it was a nightmare, so I set out to learn why it was such a pain to get truly compliant HDMI sources & sinks.

@@TookBurrow For me it really tied together a lot of loose ends having read the Specification for NTSC and H264. The progression of the scan scheme from analog NTSC to H264 ATSC and HDMI transport mediam are closely related and I found fascinating! You can take the engineer out of the office but you can’t take the love of engineering out of the engineer. Shalom JCS

Glad to hear that

You're very welcome

That is a great question. I don't know how much resistive loss is contributed by the contact resistance. Gold is great, but clean connectors are probably the most important consideration, second only to the plating material of the connectors. Personally, if I was installing I would see if fiber optic was an option. Great way to deliver signals with high integrity.

Thank You! I have received a lot of good feedback on this so I think an update video would be good. And DisplayPort makes sense

You are welcome

I use an HDMI Splitter etc > HDMI to USB 3.0 Dongle etc > PC > OBS Studio. And know how to setup/use OBS. PC gaming you need a 2nd device to lighten CPU load. Well, unless the HW is good enough.

So any chance of verifying with a known good cable? I will say some longer HDMI cables have higher wire guages and making the bend radii tricky. While very high quality cables will be fine, the cheaper ones are not full grain oxygen free. Lower reliability too. Have you considered a fiber optic cable instead? Still must be careful in routing it, but less issues over longer runs. I've also had good luck with "Blue Jeans" HDMI Cables. The use Belden twisted pairs and lots of quality testing. As for repair of existing cable, I'd suspect the terminations before in-line opens. The terminations are often poorly soldered not even meeting industry wire harness/connector standards and best practices. If the open is located somewhere in the cord, this could take some time to located.

​@@TookBurrow THANK YOU for the reply! So- you were correct - solder broke at termination. Pretty sure I pinched the cable pushing the receiver back against the wall snapping the soldered connection. Should have used a 90 degree adapter - sigh. Bought a 'solderless' hdmi connector and spliced in all the connections--bit of a hack job with limited success. Best results are - continuity throughout (no openings in wall) and AppleTV 'thinks' it can send a 4k HDR signal @4:2:0 to a 4k projector (Optoma UHD60)-@4:2:2 is the only improvement to these settings when the cable worked perfectly. It seems to work for basic menu screens and looks good playing videos in some apps but seems to choke trying to play videos in other apps. Guessing there's too much noise and it can't handle as much bandwith as it thinks? Next step might be to try soldering directly to original connector tho might be super tedious if I can pull it off. Any other suggestions? Fiber might be tricky - there are a few sharp turns with limited radius for the wire. As a last resort, I can pull the bad cable with a line attached to pull a new cable through but that's my hail mary short of busting holes in the wall (again). I guess i'm wondering if the solderless adapter is viable with better shielding? Or is this even possible to fix 'by hand' even with soldered connections to achieve the throughput i'm after? THANK YOU SO MUCH for your help!!!

@@peteb.2181 so what I've seen is that where one quality issue exists for solder (oem workmanship) / weak solder integrity there are likely more issues on the other end. Cold solder joints, pin holes in solder joints, non-wetting. Also one commonly cut corner is the shielding. It's much more expensive when properly shield from end to end. Sadly, even expensive cables suffer from this due to marketing strategies and non-compliant cables to the spec. Does the shielding inside the cable on your repaired end need to be soldered to the back shell or connector metal exterior ?

I haven't done any characterization like that for this build

@@TookBurrow Time domain?

@@jhabril this presentation was research only as an introduction into HDMI and TMDS. I didn't have any development hardware I could pin out to scope the TDMS channels with. If you find anyone who's got a good video on the Time Domain or Frequency domain please share!

That would depend on the transceiver set you are planning to use.

@@TookBurrow Meanwhile, thanks for the quick reply, you are very kind .. I should only transmit the video signal from the cam gopro hero 7 black to the screen .. but I would like to use for example only one or some of the wires inside the HDMI cable, as few wires as possible in short .. How can I do? Thanks

Daniel you say is it too complicated to instruct me in this operation? thanks

If I understand your question (and I'm not sure I do) but I think you are asking about transceiver (Rx/Tx) compatability? And other things. Please ask one thing at a time ;) So.. sources (gpu, roku, console, etc.) with HDMI version(s) mismatched to Syncs (TV, monitor, etc).... There is backward compatability in newer revisions of the HDMI standard with respect to having an older Rev HDMI (1.4a) device connected to a newer rev HDMI device (2.0a).*** *** But there is a trade off for backwards compatability, not to mention implementation oversights on lower cost ASICs (not upgradable via firmware) such as unintentional lack of support for even basic features. After the handshake between transceivers (the period of time when establishing an appropriate transmission protocol) the supported resolutions and other system capabilities are communicated to the HDMI source. The source will put out a "compliant" signal. You should know that "Compliant" signal means a lot of things. A LOT. Lol With transceivers, just stick with Analog Devices sir/ma'am. Especially if whatever you're doing is low volume production or for personal use. Or is you project simpler and just looking to purchase a more compatable set of consumer electronics?

Can you share your findings or the specification you want to base your modification off of

@@TookBurrow basically I had the idea of passing USB 2.0 through the HDMI pass though oh a product called a Gremsy T3 Gimbal, if you're interested

@@tyrian869 Is your mod idea intended for a short or long run? I recommend looking into fiber optic transceivers (encoder/decoder transmitter/reciever). Some of them can handle a lot more than just HDMI data types simultaneously so it may be a better path if you're not locked into using HDMI cables. HDMI signals can be transported over incredible lengths via FOCS without any loss / low BER

Wire Guage is leveraged only in the sense of the skin effect for high frequency types of signals transmitted through conductive materials. These signals are highly modulated (and interlaced) low voltage signals, so greater wire guage (nominal indivudal conductor diameter, non-stranded) is only important in the sense of surface area of the skin unless current is increased in the carrier to penetrate deeper the core of the wire. Many hardware differences in one HDMI revision, let alone an individual OEMs implementation of that revision.... Too many hardware (and soft core) differences to list, but it's important to mention that most IP cores (1st or 3rd party), die changes / redesigns / or new product introductions with AV oriented ASICs (or FPGAs) are done for clock cycle frequency gains and ultimately increased data through put (i.e. 48Gbps as compared to 18Gbps).

@@TookBurrowfrom which end.. the hdmi #version #support vary ... ....is it from the device side (like gpu have 1.4 hdmi support) or cable side or both...... because TMDS controller is actually #located inside the device #not inside the connecting wire (we purchase from cheap or expensive market)... please reply

DAC

Yep. There are genuinely other options out there. But if you’re dedicated or stuck with hdmi, I find that most issues can be resolved via minimizing cord lengths, use a quality switch (a/v receiver , dedicated switch). And carefully select ports that run the latest hdmi market revision (as needed) Also quality cords and connectors matter to a degree so researching and/or testing multiple mfrs cables and monitoring performance is time we’ll spent. And hd fury products are useful if you’re tackling integrator issues, or a challenging tech heavy HT setup…