Continuous handshaking problems with 2015 MacBook Pro & Denon AVR-X2200W Receiver [SOLVED]

I’ve just bought a Denon AVR-X2200W AV Receiver and it’s a lovely bit of kit, but it doesn’t play nicely with my MacBook pro 2015 over HDMI.Denon AVR-X2200W Receiver

The problem

I plug my MacBook Pro into my Samsung TV using HDMI and everything’s great. I see the MacBook Pro desktop with a great picture, no overscan, correct resolution and refresh rate – perfect :-)

However, it’s a different story when I introduce the Denon Receiver into the equation…

I use the same cable to plug my MacBook Pro into the Receiver, then (using another identical HDMI cable) plug the Receiver into the same TV using the same HDMI port. I configured the Receiver to not process the incoming signal, so essentially allow it to pass though.

This time, the TV showed a slightly over-scanned version of the MacBook display. This was fixable by dragging the overscan slider on the Mac.

However, the problem was that every four seconds the TV/Receiver/MacBook re-initialised the display which resulted in the TV going black and the connection being renegotiated, then the image of the MacBookPro desktop would come back again.

Its important to note that I’m not playing a video or running iTunes while all this is happening, it’s the the MacBook Pro desktop that’s being shown on the TV.

Observations

While this continuous reinitialising of the display was happening, I noticed a few things…

  1. The MacBook resolution didn’t reset itself, so it knew the HDMI connection hadn’t changed. If the HDMI cable had been unplugged or the Receiver disconnected from the other end, the MacBook would have changed back to it’s native resolution.
  2. The mouse pointer froze for a fraction of a second every time the TV display went black, so the MacBook was either doing something or responding to something coming back down the HDMI cable.
  3. Every time the image came back on the TV, the TV’s on-screen-display showed the resolution and frequency of the incoming signal. This suggests the signal had been stopped then started again or the TV told to re-examine and re-negotiate a connection.
  4. The AV Receiver’s on-screen-display also disappeared when the TV went black, which suggests that the source of the reset instruction is coming from the MacBook and being passed through unaltered to the TV.
  5. I swapped out all the HDMI cables and tested again with new high-speed/ethernet-enabled cables. There was no change and the same behaviour was exhibited.
  6. I tested the same AV Receiver/MacBook/Cable combination on two other TVs. A 24″ Sony and a 58″ Samsung Series 6 Plasma. In every case, the continuous re-initialisation of the display still happened.

Conclusion

The AV receiver is either altering or filtering the HDMI commands sent from the MacBook Pro to the TV or from the TV back to the MacBook Pro which is causing the MacBook pro to repeatedly send HDMI handshaking commands.

Further investigations

During my search for whether other people were experiencing this behaviour, I discovered that Apple has been quietly rolling out High-Bandwidth Digital Content Protection (HDCP) to it’s machines via OS X updates. I always keep my MacBook Pro up to date so it’s running the current version of OS X El Capitan.

It also turns out that Apple has been slowly removing makes and models of video equipment from it’s list of “supported” kit.

I can understand why Apple would want to prevent users from purchasing a film on iTunes, then “recording” it to another machine via HDMI. Unfortunately this has the unpleasant side-effect of preventing users from hooking the MacBook Pro to an “unsupported” projector or TV for presentation purposes.

Solution

After a bit of digging around online I discovered that there are a number of cheap HDMI splitters available that take one HDMI input and duplicate it to two HDMI outputs.

A side-effect of this “splitting” of the signal is that the HDCP commands are filtered out from the source signal and are not relayed back from any connected output devices back to the source device.

After reading through reviews of various products, I bought one of these splitters from Amazon.co.uk for £9.99 (with free P&P).

2-Way iSolem HDMI Switch Box     2-Way iSolem HDMI Switch Box

http://www.amazon.co.uk/gp/product/B006KZBC92

I connected the output of the MacBook Pro to the single input of the splitter and connected one of the outputs of the splitter to the input of the Receiver. I used the same HDMI cables are before.

The effect was that the TV displayed the MacBook Pro desktop just as before, but this time it no longer reset itself every few seconds.

Additionally, the mouse pointer on the MacBook Pro didn’t freeze every few seconds, so it wasn’t trying to re-check anything all the time.