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Audio sync issues between Optoma UHZ65UST / P1 and Sonos Arc with surround & Sub

  • 21 December 2020
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I’m having significant lip sync / audio sync issues with the Optoma UHZ65UST (known as P1 Pro in the US) and Sonos Arc.  I have my video source with DD+ going into the Optoma HDMI 2 port, and the Sonos Arc connected to the Optoma HDMI 1 port (ARC). The Optoma manual confirms that DD+ / ATMOS is supported on HDMI 1 port.  My Sonos Arc is paired with 2 x Play 1 and 1 x Sub (gen 2?) over wifi.

Sometimes I’m able to get the audo back in sync by switching the Optoma back to its own desktop / settings view, then switching back to view HDMI 2. This re-triggers EDID negotiation for the projector. But this doesn’t work for all video sources, and often results in losing the DD+ and ending up with 5.1.  

The Optoma does have a audio latency control, but even setting this at the maximum (-50ms) is not enough to get the audio in sync.

Any ideas or suggestions greatly appreciated. Right now I have two very expensive sets of equipment (the Optoma and the Sonos ARC + surrounds + sub) and they are next to useless.

 

 

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Best answer by Corry P 10 February 2021, 13:19

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7 replies

Annazel S
Userlevel 5
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Hi @alexp.

Thanks for reaching out and welcome to the community! Let me check it for you.

All of our home theater products, including Arc, were designed to be used with TVs. That said, some projectors may be compatible if they support HDMI ARC, eARC, or Optical. While the recommended configuration for Sonos home theater products is to connect directly to the TV, hopefully, somebody who has the same setup as yours will stop by and able to help you.

In addition, some of the community members might provide their suggestions and recommendations about this anytime soon.

 

If you have any other questions,  feel free to reach out.

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The projector essentially is the TV in this scenario.  The projector manual says “The HDMI 1 (ARC) port on the rear of the projector supports Dolby ATMOS passthrough”. The Sonos Arc is connected to it over its HDMI ARC port, and the Sonos does report Dolby Atmos in the Sonos app when playing Dolby Atmos videos. But the audio lags behind the video significantly in this scenario.

 

 

Annazel S
Userlevel 5
Badge +16

Hi @alexp.

Thanks for your response.

We don’t recommend using a projector and intermediary device to get the audio from multiple sources prior to it getting to the TV, these are non-supported setup/configuration for it ‘may’ or ‘may not’ work with Sonos. A common cause of this issue is an audio setting either on the TV or an external source device that is processing the audio before it gets to Sonos, causing it to be delayed. Check the audio output settings on your TV and any external source device, or contact the manufacturer for assistance in disabling these features.

 

You may also refer to this article that outlines the main factors that determine if your Sonos Arc can play Dolby Atmos audio.

 

If you have any other questions or concerns, feel free to reach out.

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I’m not sure what you mean. There is no TV or intermediary devices involved in this setup. The projector is the equivalent of the TV in this scenario. This signal source is plugged directly into the the projector (just as it would be plugged into a TV).  The Sonos Arc is plugged into the projectors HDMI ARC port that supports DD+. The Sonos Arc is receiving Dolby Atmos from the projector according to the Sonon mobile app. But the audio from the Sonos Arc lags behind the video by around 70ms. The projector has the ability to delay the video by up to 50ms, but this is not enough. What I want to understand is where the 70ms delay is coming from in the first place and if there’s anything that can be done to fix it.

Incidentally 70ms is the minimum group audio delay available within the Sonos mobile app for this room. I don’t know if this is where the delay is coming from or if it is unrelated.

Annazel S
Userlevel 5
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Hi @alexp.

Thanks for your response.

I understand that you are using a projector instead of a TV on your setup and this is unsupported because the troubleshooting steps we provide apply when Arc is connected to a TV.

If the Sonos device is BEHIND, and we are certain that the  Audio Delay (Lip Sync) is set to a minimum, try rebooting your source device (Projector), but if the problem continues, contact the manufacturer of the device to see if there is any additional audio processing that can be disabled. There is no setting within Sonos that will correct this issue.

 

You may also check this relevant thread that contains helpful suggestions, here is the link:

https://en.community.sonos.com/home-theater-228993/sonos-with-optoma-projector-6841124

 

Let us know how it goes and if you have any questions feel free to reach out.

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It seems you are hung up on the projector vs TV question. Let’s just say I have it connected to a TV then. There’s literally no difference. The projector is just a TV with a different display technology.

So tell me what the steps are for “the troubleshooting steps we provide apply when Arc is connected to a TV”.

I have already read the previous forum posts on this topic. There are lots of assertions that the problem is not with the Sonos end of things and that there is no latency on the Sonos end once it has received the audio signal over HDMI, but no actual evidence being provided in any of the posts I have read. For example, I’ve not seen any posts that categorically say what latency Sonos introduces in its audio signal decoding and processing, or distributing the signal across the different surround components. I’ve not been able to find any data on expected audio decoding latency or for distributing the audio to the various surround components. What are the technical specifications in this regard?

 

Corry P
Userlevel 7
Badge +18

Hi @alexp 

It seems you are hung up on the projector vs TV question. Let’s just say I have it connected to a TV then. There’s literally no difference. The projector is just a TV with a different display technology.

Personally, I agree - a projector that supports HDMI-ARC/eARC isn’t really any different from a TV, at least from the Arc’s perspective. The fact that you get any audio at all supports this.

So tell me what the steps are for “the troubleshooting steps we provide apply when Arc is connected to a TV”.

Our help page TV audio and video are out of sync describes these.

In brief:

  • Reboot your TV (Projector) and Arc - turn off at power (or unplug if no switch) for at least 30 seconds
  • Disable extra audio processing on your TV (Projector) and source device - these can induce extra delays
  • If all else fails, select the audio output format to PCM on the TV (Projector) or source device - this will disable surround sound, so is not ideal but it will clue you in as to where the delay is coming from

There are also instructions for what to do if the audio is ahead of the picture, though I suspect this is not the case.

I have already read the previous forum posts on this topic. There are lots of assertions that the problem is not with the Sonos end of things and that there is no latency on the Sonos end once it has received the audio signal over HDMI, but no actual evidence being provided in any of the posts I have read. For example, I’ve not seen any posts that categorically say what latency Sonos introduces in its audio signal decoding and processing, or distributing the signal across the different surround components. I’ve not been able to find any data on expected audio decoding latency or for distributing the audio to the various surround components. What are the technical specifications in this regard?

 

On all Sonos Home Theatre products, the audio is played as soon as it is received by Sonos. Your Arc will pass this to the surround speakers as fast as possible over a 5GHz dedicated link. I have no figures to quote, but this all happens faster than you’d be able to perceive - I personally find that anything less than about 100ms is very difficult to notice as the human brain is used to editing out the difference (light travels faster than sound) for distant events, and Sonos will be doing things at least an order of magnitude faster than that.

It is the TV’s (Projector’s) responsibility, if it is inducing delays due to audio processing, to also delay the video by the same amount as the Arc cannot play audio before it has been given it. For this reason, I recommend you make sure the TV’s (Projector’s) firmware is fully up to date and you seek support from the manufacturer or their user forums.

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
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