HDMI — making the right connection

HDMI may be a simple enough cable, but it can be the cause of many frustrations. Kris Bell explains how to keep things well-connected

WHEN LANSAT switched to IP delivery of live broadcasts last year, we found that a lot of cinemas changed their event cinema set-up to accommodate new equipment. I’ve taken a number of calls from cinemas looking for advice in setting up a reliable HDMI system that does not end up with the user doing the stressful unplug / replug / reboot dance every time you schedule a live event.

Every cinema is different, but here are things to consider when designing a system that works for you.

HDCP & EDID

This is the digital handshake that occurs between equipment. If you have a lot of items in the chain you are likely to have had problems with this. HDCP ensures that every device in your HDMI chain is secure. The two main versions are HDCP 1.4 and HDCP 2.2. HDCP 1.4 was designed for HD content, while HDCP 2.2 relates to 4K media. To view content in 4K across devices, all components must comply with HDCP 2.2. EDID is the information provided by a display (projector) to a video source, outlining the capabilities of the output device. This can cause issues, as many cinemas have multiple output devices like projectors and confidence monitors all with different capabilities. This is why we often recommend devices with EDID management.

It’s important to note that many IMBs and projectors capable of presenting 4K DCPs may not have 4K capabilities through the HDMI port. The Doremi IMB, for example, uses a HDMI v1.3 chipset limiting the HDMI to 1080p although the internal playback server outputs 4K.

Cable

The most important things you need to know are the resolution, Hz and speeds that it can handle. A high-speed HDMI cable will do fine in the majority of cases

DID YOU KNOW?

THE HDMI CHIPSET in an IMS3000 uses Dolby’s own FPGA code and so is upgradeable with a software update — so the HDMI port will stay current.

SOME IMS’S also have the option to change HDMI versions in the settings. We’ve had to do with older Icecrypt receivers that have been dusted off and disliked the IMS’s newer HDMI 2.0.

Hdmi Versions

HAVING ALL your equipment on a similar HDMI version can help the reliability of the HDCP and EDID handshake. Each HDMI version differs in the way it handles picture and sound:

HDMI 1.3: Up to 1080p at 60Hz

HDMI 1.4: Up to 4K at 30Hz

HDMI 2.0: Up to 4K at 60Hz

HDMI 2.1: Up to 4K at 120Hz and 8K at 120Hz

HDMI TROUBLESHOOTING...

HAVE YOU TURNED IT OFF AND ON...? It’s a joke for a reason. A reboot will wipe away the current state of the software and any mis-behaving code. With HDMI, there are a lot of digital handshakes between devices and EDID management, so a reboot is often a good first fix.

CHECK/RESEAT CABLES… It can be weeks between HDMI screenings. Things get knocked or unplugged. Check status LEDs on equipment and that power is running to all equipment. A handy tip: before you unplug too much, take some photos so that you can put it back again.

TRY A DIFFERENT SOURCE… This will quickly determine if the source is the problem. Take the HDMI cable out of the back of the source device and plug it into something else.

audio. On many alternative sources, the audio can be encoded differently (Dolby Digital / Dolby Digital Plus/ DTS etc) which is why often the HDMI is looped through the cinema’s audio processor or the Bit-stream audio is de-embedded on a digital coax cable which is then sent to the audio processor.

HAVE A MONITOR IN THE BOOTH… Check the monitor will accept the signal your projector is expecting (in most cases a 1080p monitor will do). Plug the HDMI from the source directly into Monitor 2, check the settings on the source device are outputting what your projector and audio processor is expecting. Then add equipment like a splitter/ HDBaseT links into the chain to narrow down the problem. Try to use the same cables; they can often be the culprit.

STILL STUCK? CALL OMNEX SUPPORT… Often, doing the above will resolve issues but if it doesn’t then our team is on hand between 8am and 10pm every day.