Please add audio delay for HDMI inputs on Atem Mini series

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joefish

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Please add audio delay for HDMI inputs on Atem Mini series

PostSat Oct 16, 2021 4:25 pm

Hi,

It's great that we have the option to add audio delay to mic input signals on the Atem Mini series.
However, I really hope you can add the same adjustable audio delay feature for HDMI inputs as well.

For me, the main reason for asking this is to get rid of mic/audio input interference and noise issues. I've been having problems on multiple locations when connecting external audio to my Atem Mini & Atem Mini Pro ISO. Probably due to grounding issues and the fact that the mic inputs are unbalanced. The ground noise can get really loud with these Minis.

We could easily go around this issue by using optical S/PDIF audio together with an audio to HDMI embedder, effectively adding galvanic isolation and bypassing unnecessary D/A and A/D conversions. However using this method will of course offset the audio, and currently there's no way to fix this inside the Atem Mini's internal mixer.

In case there's not enough horsepower for this in the hardware, I'd really be ok to be able to delay two audio inputs only. Just add the option to select which ones.

Thank you for your work, and hopefully you'll be able to make this happen. ;)
Last edited by joefish on Sun Oct 17, 2021 10:01 pm, edited 1 time in total.
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Frank Engel

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Re: Please add audio delay for video inputs on Atem Mini ser

PostSun Oct 17, 2021 10:40 am

If I am correctly understanding the problem, delaying the audio within the switcher would go backwards from what you would need - if the extra processing is already delaying the audio compared to the video, then adding more delay would push it even further away from the video.

You would need to delay the video signal to match the audio, which requires beefier hardware than delaying the audio would.


If I am misunderstanding and the different processing path you are taking is causing the audio to get ahead of the video, a workaround while waiting for this might be to de-embed the audio close to the switcher and bring it into one of the analog inputs which does have a delay.

Another option would be to place an audio delay unit before the HDMI embedder.
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Howard Roll

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Re: Please add audio delay for video inputs on Atem Mini ser

PostSun Oct 17, 2021 10:52 am

When interfacing with external consoles unwanted rf is inevitable. Not every time of course but one does this in varied environments then it’s going to happen often. The bigger the production the better the chances of a bad transformer or ground causing havoc.

Sesscom makes a few iterations of IL19, there’s the Jensen Pro Max Line, the Henry Matchbox, these are a few of the standard hum eliminators. These will solve the problem without necessitating the delay.

Good Luck
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joefish

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Re: Please add audio delay for video inputs on Atem Mini ser

PostSun Oct 17, 2021 1:30 pm

Frank Engel wrote:If I am misunderstanding and the different processing path you are taking is causing the audio to get ahead of the video, a workaround while waiting for this might be to de-embed the audio close to the switcher and bring it into one of the analog inputs which does have a delay.

Another option would be to place an audio delay unit before the HDMI embedder.

Yes, you seem to have misunderstood. HDMI video output from a camera is always delayed. Audio from a mic / digital mixer console / audio interface usually is not. (unless ran through plugins that introduce latency). That's exactly why we have the option to add delay to mic inputs in the first place.
If a mic is plugged directly to a camera, the audio is delayed the correct amout inside the camera already so it's in sync when fed out from the camera's HDMI output.

Audio to HDMI embedder / inserter does not delay audio. It simply inserts the audio to the HDMI stream (replacing the audio fed to it's HDMI input alongside video), so video signal from HDMI cameras will always be delayed compared to directly fed audio.

We could of course use a separate digital to analog converter right before the Atem Mini, but that does not change the fact that unnecessary D/A + A/D convertions take place here, and again this introduces the possibility of grounding issues. There are ways around this of course, for example using a hum eliminator like Howard mentioned above. However these cost money and the other main point was to avoid audio quality degradation.

We use pro quality analog to digital converters, mix live music and audio with pro quality gear, that's then fed to Atem Mini's consumer quality mic inputs and A/D converters. This is by no means badmouthing the Atem Mini hardware. I fully understand that for this price range, and in addition to the already mind-blowing feature set we cannot have pro quality audio as well. Pro A/D converters alone cost a lot of money.

I'm just saying that there would be an easy (and cheap) way to get rid of any grounding issues and retain pristine audio quality bypassing the Atem Mini's mic inputs and audio conversion stage alltogether by using a digital to digital HDMI audio inserter. There is no conversion whatsoever taking place inside these audio embedders when fed with digital audio. Delaying the audio would be most gracefully handled within the Atem Minis, as they are already cabable of handling this task (currently on the mic inputs only) without the need of external audio delay units.

I mean one of these very affordable babies:
https://www.ebay.com/itm/233910095321

https://www.aliexpress.com/item/32984747683.html?spm=a2g0s.9042311.0.0.24344c4dE03BUr

https://www.blackbox.com/en-us/store/product/detail/Audio-Embedder-De-embedder-HDMI-2-0/AEMEX-HDMI-R2
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Blair Christensen

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Re: Please add audio delay for video inputs on Atem Mini ser

PostTue Oct 19, 2021 10:00 pm

joefish wrote:Yes, you seem to have misunderstood. HDMI video output from a camera is always delayed. Audio from a mic / digital mixer console / audio interface usually is not. (unless ran through plugins that introduce latency). That's exactly why we have the option to add delay to mic inputs in the first place.
If a mic is plugged directly to a camera, the audio is delayed the correct amout inside the camera already so it's in sync when fed out from the camera's HDMI output.

Where do you get the idea that HDMI video output from a camera is always delayed? Have you actually tested the solution you've come up with? You may be trying to solve a problem that doesn't exist...
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Mike Wallis

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostTue Oct 19, 2021 11:04 pm

In my experience with Canon camcorders the vision & audio is always delayed via the HDMI inputs. Wherever you have video processing you usually end up with a delay and it all adds up.
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bm1867bm

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostWed Oct 20, 2021 12:12 am

I cant confirm this, but heard someone say recently that the latency/delay on hdmi from Blackmagic cameras to an atem (assume BMPCC4K was what he was referring to specifically) is very low. Most other cameras (with only hdmi outputs) have a significant delay. The ATEM minis did not even have a delay function on their analog inputs when they were first released. Maybe the importance of this was missed if Blackmagic mostly tested the minis with their own gear.

I have had heard others say they would find being able to delay hdmi inputs helpful in some cases. I to date have not needed this. It might be hard to be able to delay 8 inputs, but maybe being able to select one or two inputs would be doable.
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joefish

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Re: Please add audio delay for video inputs on Atem Mini ser

PostWed Oct 20, 2021 1:04 am

Blair Christensen wrote:Where do you get the idea that HDMI video output from a camera is always delayed? Have you actually tested the solution you've come up with? You may be trying to solve a problem that doesn't exist...

Thank you for your reply, but did you actually read my posts? As I mentioned, the main problem is that I get noise from the mic inputs when using external audio mixers and interfaces to mix and feed audio to my Atem Minis, so quite obviously the problem does exist.

And about latency.. I get the idea from having used cameras for about as long as HDMI has existed. I have yet to encounter a camera that renders it's sensor feed to it's HDMI output with 0 frames of latency. Please let my know if you know of one. I've heard that Blackmagicdesign cameras do get pretty close, but I don't have one yet, so I can't try it myself.
The Canon and Sony ones I'm currently using have a latency of about 4-5 frames, which is enough to offset the audio so that it looks like the drummer is holding his drumsticks up in the air, when in audio we hear the stick hitting the drum. (Just as an example)
Blackmagicdesign also recognizes this offset. Why on earth would we have the option to delay the mic input signal, if this camera feed to HDMI video latency would not exist?

I simply hope that Blackmagicdesign developers can add this feature, as I believe it's doable and would be very useful for me and many others. And Blair, isn't it great that you don't actually have to worry about the features you don't need yourself? ;)
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ManchesterV

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostWed Oct 20, 2021 3:45 pm

Send the audio to a camera input. It will arrive in sync with the video via HDMI.
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joefish

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostWed Oct 20, 2021 11:25 pm

ManchesterV wrote:Send the audio to a camera input. It will arrive in sync with the video via HDMI.

I fully understand I would get audio synced this way. Unfortunately this is not always possible. (my mobile setup cameras don't even have mic inputs) And also again we'd be adding an extra D/A + A/D stage. Now we would simply be using the in-camera converters instead of the ones in Atem Minis.

I appreciate you all trying to help out, but I actually thought this through before posting here. I'd find being able to delay the HDMI audio a very useful feature in multiple scenarios. Not only for getting rid of audio interference.
If this can easily be added, I hope it will be..

All the best,

Joel
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joefish

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostTue Nov 30, 2021 8:46 pm

I can now confirm that the HDMI audio-embedder works perfectly for getting rid of any audio issues. (at least when using optical S/PDIF audio.) The signal path stays all digital after the separate a/d converters and digital mixer stage, so we get bit perfect audio to Atem Minis without any quality degradation.

It’s possible to delay the audio before feeding to HDMI-embedder and Atem mini, using for example this free plugin: https://www.voxengo.com/product/sounddelay/

However, I would much rather have the Atem mini hardware handle delaying of the audio, not having to route the audio through my laptop and daw at all times.

So I repeat my wish, please add the option to delay HDMI audio to Atem mini hardware.

Thanks again!
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bhwhumphries

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostThu Dec 02, 2021 12:08 am

You haven’t mentioned what audio mixer you’re using. However, in my scenario (x32 rack) I can add delay to the audio within the mixer so solve the problem that way. But I appreciate your mixer may not have that function.


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Raphaël Jacquot

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostThu Dec 02, 2021 6:09 am

what you really want is some Behringer FBQ100 modules
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bhwhumphries

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Re: Please add audio delay for HDMI inputs on Atem Mini seri

PostThu Dec 02, 2021 10:12 pm

Raphaël Jacquot wrote:what you really want is some Behringer FBQ100 modules
No digital in/out though?


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