Panasonic HDMI 2.1 boo-boo – dark times for Xbox Series X & nVidia users

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(For anyone who frequents the TWiT Discussion community, I posted this there as well)

I was just reading the current issue of c’t (the leading German language computer magazine). They had been doing tests with the new Xbox Series X and nVidia RTX30xx series cards. The problem is not with the Xbox or the nVidia chips.

The problem come from Panasonic. They developed the HDMI 2.1 chipset used in many amps, from Onkyo, Panasonic, Pioneer, Sony, Marantz, Denon, Yamaha & Co. and, possible Samsung TVs.

TLDR; connect the Xbox Series X, nVidia RTX30xx directly to a HDMI 2.1 capable TV and you will be fine, connect it through a current generation HDMI 2.1 AV receiver or other “switcher” and you will (probably) get a black screen. The problem occurs mainly in 4K 120Hz mode and especially with HDR.

The problem shows itself when using 4K120 HDR or 8K120 HDR. The problem seems to come with the switch from TMDS (Transition-Minimized Differential Signaling) to FRL (Fixed Rate Link) in 2.1. The signal from the Xbox and nVidia chips uses a certain pattern (*correctly*), but the Panasonic chipset interprets is incorrectly and you are left with a black screen.

c’t was testing Dirt 5 on the XBox Series X and everything was working fine, when directly connectd to an LG CX9 TV. As soon as they put it through a Denon AVR-X2700H HDMI 2.1 capable AV Receiver, they just got a black screen.

The PS5 is allegedly not affected, while it doesn’t use this specific pattern when generating images.

There is a weak point in the new HDMI 2.1 specification, but also a further bug in the Panasonic chip used by most AV Receiver manufacturers.

It seems it is a combination of FRL and DSC (Data Stream Compression) that leads to the problem in the Panasonic chipset. According to the c’t article, a firmware update for such devices is not possible. Microsoft is aware of the problem, but the first batch of Series consoles are using finalized hardware. c’t will test again using a retail example, not the preview model they received for testing.

Now they are looking to see how Microsoft and the receiver manufacturers communicate and deal with the problem. The most likely effects will be a motherboard swap for affected AV receivers or delayed release dates for receivers that aren’t already on the market, to correct the problem.

It might also be possible to use TMDS mode to generate 4K120 images with reduced defintion (TMDS has a maximum transmission speed of 18gbps, FRL runs at around 48gbps), which isn’t in the HDMI standards committee’s specification.

Another problem, with the specification, is that there is no defined standard for transmission, devices can used compressed or uncompressed feeds as they wish. Some receivers however don’t support uncompressed feeds – Xbox Series X, PS5 and nVidia RTX30xx all use uncompressed feeds.

The original article is behind a paywall, here is another site’s report on the original article (German):

https://www.heise.de/select/ct/2020/23/2028412014308611632

https://www.computerbase.de/2020-10/hdmi-2.1-bug-av-receiver-konsolen-grafikkarten/

Comments (11)

11 responses to “Panasonic HDMI 2.1 boo-boo – dark times for Xbox Series X & nVidia users”

  1. bschnatt

    Thanks for the info. Good to know...

  2. north of 49th

    I get that everyone wants to be first to market, but if you don't have robust end to end testing with good range and depth of source material, this is what happens.  The receiver manufacturers should have waited and I feel for the early adopters.

    If the HDMI implementation includes Enhanced Audio Return Channel (eARC) perhaps it is possible to push the Xbox or PC video/audio direct to TV and let the audio pass back to the receiver. As a work-around, it would complicate the switching - perhaps add a harmony remote?

  3. madthinus

    As someone running a decade old AV setup that is connected to a 1080p TV, this is rather bad news. I am getting a Series X and upgrading is going to be a phased approached. I was thinking of buying the AV receiver first, as TV's with variable refresh rates are still few and far between. Looking at the total cost involved here, I might have to wait a while for all of this to settle first.


    As for the Panasonic chip: It might be that they have build a compliant chip to the specification, but due to unclear specification left stuff to interpretation. My AV receiver at present list in the manual a range of errata when it come to HDMI as well. So I guess this is rather normal. I guess HDMI 2.2 will fix these.

    • wright_is

      In reply to madthinus:

      No, according to the c't article, it is a bug in the implementation. There are additional bugs in the actual specification as well, but this specific problem is purely down to a fault in the Panasonic chip, when it is hit with a specific "pattern" or combination of resolution, refresh rate and HDR, they all work individually, but together the chip just craps out.

    • Chris_Kez

      In reply to madthinus:

      I completely sympathize with anyone else trying to update their existing 1080p set up. Does it support HDMI 2.1.? Which specific features? VRR? E-arc? How about HDR 10+? Dolby Vision? It starts to feel a bit like this:

    • Chris_Kez

      In reply to madthinus:

      p.s. Rtings has a nice list of TV's that support VRR. If you're getting the Series X this holiday season and can only upgrade either the TV or the AV receiver, I would suspect you'll appreciate the TV upgrade much more. I presume you could connect the Xbox to the new TV, then route the audio via e-arc to the receiver for the audio. Yeah, it means another remote for switching inputs, but maybe the short-term pain would be worth it to enjoy those games in 4K HDR? Good luck, and enjoy either way!

      p.p.s. My wife has gotten me both the Xbox One and the Xbox One S as Christmas gifts and I've returned them both because I just don't have time to game. I wonder if she'll try a third time with the new Series.

  4. Greg Green

    Since we’ve moved to Georgia, where there are thunderstorms, I’ve had problems with my HDMI connections. One plasma TV disabled (twice) because hdmi no longer works, and a receiver that lost hdmi 1. HDMI has now become my least favorite connector.

  5. lezmaka

    Makes me glad I upgraded when I did, rather than waiting a couple years just to end up with buggy HDMI 2.1.

  6. north of 49th

    Interestingly, Anthem AV (A higher end AV equipment company) just released their new line of Receivers/Pre-pros and they specifically call out that their equipment is HDMI 2.0b – hardware upgradable to HDMI 2.1 when the hardware matures.  

    Granted you pay more for their equipment, but having the transparency to call out that the HDMI standard needs time to mature and purposely building in a hardware upgrade path to their equipment is the right thing to do for their customers in my opinion. 

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