HDCP problems with Imac - or other output trouble



I had a gig yesterday at a music festival, using VDMX from my Imac (2021, Big Sur).

All my files were HAP, some of them quite large / lengthy (10 min).

I connected my device to the video projector of the festival venue and boom, my problem started within less than 5 minutes:

  • The connection to the output (the projector) was interrupted / disturbed / broken repeatedly and my Imac thought there’s no longer screen number 2. Therefore, the main output window appeared on my screen number 1 (= my actual Imac screen), on top of the VDMX windows, unabling me to handle VDMX at all. All I could do was to force quit the programme, reopen and start anew. This kept happening all through the show. (Yes, you can imagine my stress!)

  • Imac was connected to Kingston adapter, which had a HDMI cable running to the Roland video mixer of the venue and that with another HDMI to the projector

  • I have used VDMX with the same Imac and same project and same files before in other venues with absolutely no trouble at all. Testing with a monitor as second screen at home also was smooth and no problems occured.

  • We switched adapters and cables and booted my Imac and checked everything, problems remained.

Today I asked about this from VDMX support and got a reply with an explanation that this is most prob caused by the HDCP issue of my Imac (= High-bandwidth Digital Content Protection, an anti-piracy protocol). There is no way I can switch the HDCP off, I suppose, from my Imac, so what I need for future gigs (cause I sure don’t want this to happen AGAIN) is a way to prevent this in some other way.

I was suggested to use a signal converter / scaler / switcher. Any ideas on how to use one? I never had one and have no experience in using them.

Since the venues change, I would love to learn how to keep the HDCP problem not ruining my show in our upcoming concerts.

Many thanks, M



Hi @viitah,

Thanks for bringing this to the forums. There are a few ways to “break” the HDCP chain. One is to use something that doesn’t send HDCP, such as VGA. You could do a VGA dongle and run cable directly to the projector. Another is to use an HDMI splitter device (google for more on that). HDCP is a legal requirement that several manufacturers put into their hardware. I’m not sure which projector you are using, but sadly there could be several factors for why your signal was dropping (along with HDCP).

I may have dove into this before in the forums talking about EDID devices, but it will be good to go over again.

For example. I’ve had quarterly gigs at the 9:30 Club in D.C. for the past few years (minus covid shut down). I first went there with my 2015 MacBook Pro (OSX 10.12.6)(MBP), and had no issues using the HDMI out built directly into the Mac. This then went into a Decimator HDMI to SDI > 100’ SDI cable > BlackMagic SDI to HDMI > HDMI into the Projector. We never had a problem with drop outs when I forced my resolution to be 1080i60 with Switch Res X (This was an older projector and liked Interlaced frame rates).

Enter M1 Max MBP with OSX 12.1 (and the fancy yellow dot). This computer has an HDMI out, and no matter what cable, port, or resolution we switched to, the projector would experience frequent dropouts of signal (enter the momentary blue screen of death). Plugin a Windows PC — no problems, but plugin a newer mac and it took anywhere from 5mins to 45mins before the screen would experience dropouts.

So what happened? Well, there are several possibilities. For one, Decimators and BlackMagic (BMD) converters can conflict depending on their settings. Even models (older Decimators vs newer, BMD converters, etc.). It was an older projector, so there’s a good chance it was asking for a specific resolution from the BMD SDI to HDMI converter. A lot of broadcast hardware (Roland V-1HD, Decimator, BlackMagic) stick to broadcast resolutions and do not support native computer or projector resolutions (WUXGA 1920x1200 for example). So you have to tell them all to work with a standard (such as 1920x1080p29.97 or 25 Similar for NTSC/PAL).

I emailed Decimator about it and they said the only device that officially supports computer resolutions is the 12G-Cross (we were using the MX cross converter).

There’s a point between each of these devices where there is a “handshake” to share information, and it has to happen fast for low latency.

So the mac talks to the Decimator, and the decimator says here’s my EDID (I can accept all these resolutions), then the mac outputs one automatically. Then the Decimator talks to the BMD device that says, I can accept this signal (meanwhile the projector is talking to the BMD device too). So if something is off with the “handshake” it can cause intermittent blackouts or blue screens of death.

The problem with Macs and HDMI is depending on what is running on the Mac, it may require HDCP to connect over HDMI to an external device. If this happens, and it bounces into the handshake of one of these devices (or in your case the Roland V-1HD which I also own), you can experience a drop in signal while the mac sends HDCP, it gets denied, it drops the signal to the next device in the chain, on and on until the projector starts “searching for a signal” and the process repeats until your devices are connected.

This is where a scaler / switcher comes into play. When we used an older Barco ImagePro: https://www.barco.com/en/product/imagepro-ii-series

The 2022 MBP HDMI went into the Barco over HDMI, the Barco then went out directly to the BMD device over SDI. The signal never dropped. Because the Barco device is a scaler / switcher with it’s own power, even if the mac drops signal (which it didn’t), the Barco would remain connected to the projector.

The Roland V-1HD doesn’t seem to act the same, and I’ve experienced a similar dropout as you have with my Roland on multiple occasions. (I’ll have to follow up with Roland about this). You can force HDCP on or off with the Roland, but that may or may not work with your given projector setup.

In your email you mentioned a very long run HDMI cable, that can also be an issue if the signal is weak to the projector.

In the end, I had 9:30 club replace their Decimator with a Lumantek HDMI to SDI converter scaler: http://www.lumantek.com/index/product_intro/62

This essentially replaced the rack mount Barco Image Pro.

Lastly, some HDMI splitters (brand name and generic) use cloned EDIDs. From time to time an EDID will get blacklisted if it is being used to “breaks” HDCP. When this happens, the mac will cause issues connecting to that device.

It should take some time to troubleshoot the problem. Resolution, cables, dongles, to projector source settings, and so on. There are a few things to think about before going to your next gig.

I carry an extra bag with HDMI splitters, capture devices, and BMD cross converters in case I run into this problem. Luckily, I’ve been sticking to the same venues and know their setup at this point.

Hope this helps!