HDMI Latency Myth Busted

Does HDMI add significant delays to your video signal? We find out...

Video editing by @wittyfilmgirl

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#hdmi #videoproduction #latency #blackmagic #videodelay #blackmagicdesignatemmini #sdi #sony #crewaxis #switcher #atemmini #liveproduction #livestream #djp #hdmidelay #oledmonitor

[TheThreeTechs]

ATEM Mini input 1 is “direct switched” to HDMI out for low latency gaming use cases. Try measuring ATEM delay with inputs 2-4.

Also note that using higher frame rates like 60 FPS vs 24 FPS will give you lower absolute latency when measuring in ms instead of frames because a single frame buffer at 60 FPS is 17 ms (1/60s) delay but the same frame buffer at 24 FPS is 42 ms (1/24s) of delay.

[aaronpk]

Looks like you confirmed the delay! One frame of delay in the conversion, but that's a best case scenario since you're using a SDI-HDMI converter. The ATEM Mini not adding additional delay is encouraging though.

[Daniel-qrdq]

I'd be interested to see the same test, but with HDMI out from the camera converted to SDI, and both SDI and HDMI directly out of the same camera for reference. I'm also aware that Black Magic converters reclock the signal.

[HackingHollywood]

Great test. It would be amazing to have the manufacturers start generating some sort of video output delay test (kind of like what they do for computer monitors in mil-seconds). That way we would know roughly what the delay is for each HDMI camera, and then be able to resync audio if necessary. I know there will probably be some tolerance because each camera will still be slightly different, but 99% of people will only notice if its more than 2-3 frames out of sync in my experience.


I use 2 FS5's which have 3G-SDI outs. I was a bit bummed to figure out I could not get a 4k signal out of the SDI (learned about 12G/6G/3G etc from Doug). I ended up getting Atomos Shogun Infernos, which can take a 4k HDMI signal and convert it into 6G SDI, so now I have the best of both worlds. the HDMI cable is 1 foot to the 7 inch monitor (which is way better than the built in one), plus I have a super 35mm sensor with a servo zoom lens (28-135mm F4.0).


I'm working on a comparison spreadsheet for live video. It's currently got over 3, 000 data points, 100+ cameras with 30+ features listed for easy comparison between models, frame rates, outputs etc. Will update you when it's done Doug! I'm using airtable, so it's super easy to filter, group, and sort. I want to possibly create a resource the live video community can open source/help update so we can compare gear better and faster, so we spend less time researching and more time shooting!

[DNKSLegacyProductions]

Try to keep a balance of both because when it comes to the real technical stuff on equipment your channel has been the most accurate and beneficial to me. If your beginner stuff is as good, there will be no need to watch anybody else. You have solved many technical problems for me. For example many channels tell, the technical max length for HDMI cables so I followed those guidelines. The cables never work properly I kept running into reliability problems: sound with no picture, picture no sound, both pic and sound but then signal drops, etc. I purchased several sets trying to get better cables, with each subsequent set costing more. It wasn't until I watched one of your videos, that I found the actual reliable length for HDMI and I switched to SDI for what I needed. I still do use HDMI but never more than 15 feet because with dongles for converting size and camera monitors and converters I do want to stay under the limit. Icing on the cake you told me the right kind of SDI cables to get. Glad to get more from you. Keep up the good work. I am definitely a fan and I have learned a lot from you, thanks.

[Mojaxx]

Thanks for this Doug. I think I’m amongst the many people who’ve never worked with SDI, and therefore believed what we’d heard about HDMI vs SDI.

Correct me if I’m wrong though, but you did just demonstrate that BOTH have a significant delay, right? Which is why audio sync is an issue with external audio devices on the Minis.

And I’m not sure I understand your comment about games consoles. As I understand it, a delay of audio and video (together) of a few frames wouldn’t have any impact on a game... Only a lag in control input would cause that. So the delay caused by HDMI/SDI is no issue. Or have I missed something?

[moomamedia]

Hi Doug. Great, real world test! May well have been said in previous comments, but I’m pretty sure a lot of this myth comes from disparities in camera output latency on mixed camera systems, particularly with a lot of folk using units like the GH5 for B-cam, which is well known for output latency. Always love your videos, BTW, so nice to be spoken to rather than shouted at! :)

[AmauryJacquot]

in your test, you get one frame, because the converters add a line or so each.
that leads to a de-synchronization between input 1 and 2, the monitor thus adds 1 frame latency to be able to display both images side by side on the same screen
the real issue is not the hdmi itself, but the processing in various consumer level equipment.
DSLRs have between 4 and 6 frames latency, consumer tvs have the same (which includes useless "AI image improvement" and the like)

[dannypgrizzle]

PhotoJoseph (YouTube moniker) is my source of accusation of HDMI latency. His problem stems from audio delay that prevented him from monitoring audio while speaking as on camera talent. He solved this by switching to SDI on a Blackmagic Micro Studio Camera 4K, which solved the problem so that his voice was heard on ear bud monitors in real time.

[mondotv]

The test isn’t valid. Latency has nothing to do with the cable but rather the time the camera takes to convert the signal to HDMI. Using a cross converter won’t work either as those devices typically use chips that are much faster at converting. What you need is to compare a camera like the Sony FX6 outputting SDI against a say a Sony A7 series camera outputting HDMI pointing at a timecode reference. I’m not sure how much of a difference there would be but as others have pointed out, the GH5 has a significant delay on it’s HDMI output.

[timmccormick]

We have always run into issues when deploying video monitoring of a Maestro / Conductor so that a singer viewing at an off angle or from another location can sing in time with the orchestra. So, I never did this level of testing - and I totally appreciate the work here - but having tried to move our systems to digital without telling the musicians we get notes about how the singers are getting behind or off the beat. I can't quantify the frames-per-second but it has seemed that any latency at all is problematic for live classical musicians.

But ... if HDMI as a format isn't the culprit but rather the conversion for long runs of HDMI/SDI - SDI/HDMI ... can you do a video on the gear you recommend for a near zero latency digital setup?

[computerjantje]

I have 5 the same camera's that run at 50frps. Three come to the switcher by hdmi (1 to 10 meters max) and two come to the switcher by converting to sdi at the camera and back to hdmi just before the switcher. The delay that happens is not noticeable different for the camera's that come in over hdmi as over sdi. There is 4 frames delay in the switcher compared to the direct sound that is coming to the switcher from my microphones through an audio mixer. My guess is that the camera causes the 4 frames delay and not the hdmi and/or the conversation to and from sdi. I always 'blamed' the camera for the delays but good to know it has nothing to do with hdemi :) I was rather surprised that the hdmi-sdi and sdi-hdmi conversion at the other end of the long cable, did not add any noticeable difference between the camera signals. :)

[crooker]

You and me are the same. Love live video production, video, equipment, and methodology. But hate editing video. Haha. Too tedious. I get more adrenaline by doing live TD (which, fortunately is now happening more and more)

Love the videos. Keep them coming.

[huyked]

8:47 Yay! We're on the same boat! :D lol. I wish I wasn't on that boat, but whatcha gonna do? ;D
Thank you for this test and explanation.

[tvpluskumanovo]

Conversion is not the problem, try using 2 cameras, one on sdi one on hdmi on 2 inputs in ATEM and than look in the multiview from the ATEM.

[gustersongusterson]

HDMI has a higher color bit depth than SDI right? So if you don't have a need for long runs isn't the color better slightly? Can you see the difference, or is it at the very least enough to affect chroma keying? I've really enjoyed your more advanced stuff, but there are so many misconceptions in our industry that going through the basic stuff can be quite enlightening sometimes. Looking forwared to more of your videos!

[wasbeen]

I remember ATEM Mini input 1 being special, and having the option of direct pass through to the output. Would be interesting to see if your setup could tell the difference. My guess is the other inputs sync to input 1, so that one stays least effected. Maybe only shows once multiple inputs are already synced. Really don’t want to confuse the topic, honest.

[shyamgupta]

Dough what I have noticed is the problem comes when hdmi is directly coming from camera. In your test setup the feed is coming via sdi than its getting converted by BMD converter.

[marcobillardello]

Very interesting video, but I have a question for you. If I make a multicam with three cameras, two entering the atem via hdmi, and one entering via a wireless transmitter like the mars400, how do I delay the two hdmi input cameras so that all three are in perfect sync?

[crooker]

So... How does cable length affect latency? Is there any more latency over a 50' 3G-SDI cable than a 100' or 150' cable? We do 50' cables mostly, but with more and more productions coming in, the need to expand our system will become more prevalent.