Original topic:

Q90T: Dolby Digital audio lag over optical

(Topic created on: 1/24/21 1:26 AM)
keithfkelly
Cosmic Ray
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4k, 8k and Other TVs

My setup: Xbox One S (4K HDR VRR  + Dolby Digital bitstream) >> Samsung Q90T (game mode on, audio output optical) >> Yamaha RX-V673 receiver (DD decode to 7.1)

Audio lags a distracting amount behind the video.  It's so distractingly bad that 4K UHD content with surround sound is basically unwatchable.  The only "solution" I've found is to completely bypass the TV audio by connecting the Xbox One S optical output directly to the Yamaha receiver's optical input.  But this isn't a general-purpose solution; I have other devices (HTPC and PS5) that do not provide optical audio outputs at all.

I cannot run HDMI through the receiver and into the TV because the receiver can't handle or pass through 4K video at any refresh rate other than a fixed 24Hz.  I cannot extract optical audio off any HDMI 2.1-producing device, because nobody in the world right now makes an HDMI 2.1 audio extractor.  I cannot use eARC to the receiver, because the receiver does not support eARC... and even if it did (or I were to use a ThenAudio SHARC eARC converter), that apparently wouldn't work due to another known Samsung Q90T bug wherein it won't pass anything other than uncompressed stereo over eARC.

So, the optical output off the TV is my only option for using my PS5 or HTPC with this combination of TV and receiver... and I'm stuck choosing between horrendously obnoxious audio lag, or no surround sound, neither of which is acceptable.

Samsung needs to quit being lazy and/or opaque about this problem.  They need to publicly acknowledge that it is a known defect with this series of TVs and tell customers when we can expect an updated firmware that will fix it.  The optical audio output lagging behind the video is unacceptably broken functionality, especially for a television that costs this much.

Do any Samsung employees actually read these forums?  If so, can you please provide a status update regarding this problem?  I see numerous similar community reports that all boil down to this same issue... and they all have pages and pages of irate customers saying "me too!", but zero acknowledgement from Samsung.

I need to know when I can expect to see an updated firmware that fixes this issue.  And if you aren't ever going to provide one, then I need to know what you're going to do to make things right by me -- such as refunding 100% of my hard-earned money so I can go buy some other brand of TV that actually works correctly.

6 Replies
userOBq4tN1YOO
Constellation
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 I have a similar problem with my 58" 700 series Samsung...optical output from TV to input of my Pioneer surround receiver. The video is slightly ahead of the audio....TV audio delay setting only allows further delaying the audio, there is no way to speed up the audio  to sync it perfectly with the video.  From what I've read some other brands have  + and - audio delay settings in their settings menu. I would think that Samsung could do an update and add that to the audio settings instead of just the - settings. 

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userCtLecu9x58
Constellation
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This is a good post, lots of info here.

We have a new Q90T and I have been trying to get things set up to give us surround sound. Started with a J-Tech switch/extractor, a SWE41, but can't get it to pass video or audio. So started fooling with the TV's optical output. Finally figured out that to get more than PCM 2-channel out over the optical you have to enable eARC. The pass-through setting in the menus is grayed out (maybe because no eARC device on the other end of the cable?), so I set to Auto, now I am getting AC3 over optical for all my sources (cable box, Apple TV, and apps running on the Apple TV and also on the TV). At a glance I do not notice a visible lip sync issue, but will keep an eye on this.

Also figuring out best place to run apps, Plex, Netflix, Amazon Prime, etc. Last TV was also a Samsung and had the Smart Hub/Apps stuff, but it was so slow it was painful so we used the Apple TV for everything. Plex on the Apple TV is stuttering badly, not sure why, maybe the server thinks it needs to do some (up)scaling. Plex running on the TV is smooth and snappy. So maybe we need the Apple TV less.

I am running the optical from the TV into a Meridian G61. Would love to have SPDIF, but practically I am stuck with optical unless I want to buy a Meridian 722 for $2k. Funny, Optimum cable box, a SMT-C5320, can only output 2 channel on its optical output. But the TV is happily sending AC3 5.1 for most channels.

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keithfkelly
Cosmic Ray
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These Samsung TVs are not capable of doing Pass-through over optical, only over eARC.

Running anything other than Stereo uncompressed over the optical port in Auto or PCM mode will result in bad audio lag, because the TV must decode the incoming audio stream and then re-encode it to send it over the optical port (that is what Pass-through avoids doing), which takes some very noticeable processing time (due to either a Samsung firmware defect OR an anemically-underpowered CPU inside the TV).

I bought a Thenaudio.com SHARC to solve this problem.  I can confirm it works great with the Q90T, enabling the TV to pass through DD 5.1/7.1, and even 7.1 LPCM from my PS5, over HDMI3(eARC) to the SHARC, which then passes it through to its own optical output (straight into my old non-eARC non-Atmos AV receiver) with no noticeable audio lag.

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userCtLecu9x58
Constellation
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Haven't done much watching yet but honestly it is hard for me to see audio lag with this setup. If I look really hard I can convince myself that I see a little lag. My wife, who is not a nerd and not privy to this navel gazing, has not said anything yet, if she notices audio lag then I will get on the bandwagon.

With audio set to TV speakers optical is PCM 2.0, so if you play something with DD 5.1 (with Plex you can select the audio stream) the TV has to decode/encode the optical to send out 2.0, so I don't see how that would have less lag than if you change the audio setting to optical and output to Auto and get 5.1 over the optical. It does seem a little strange that to get AC3 over optical you have to enable eARC in the settings.

Larger issue for me is maybe that with audio output set to optical the TV will not send sound to the TV speakers, and I like to be able to use the TV speakers for casual watching/listening. Question, does connecting an eARC device (like the Thenaudio) un-gray out the Pass-Through option and if so, when you select that can you also use the TV speakers?

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keithfkelly
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> With audio set to TV speakers optical is PCM 2.0

Yes, because even when you have not selected Optical as the output, the optical port will still always send audio in whatever format is being used for the selected output.  Regardless of whether this behavior is a feature or a bug, it's caused a lot of user confusion (e.g. Why can't I get DD/AC-3 to come out of my optical port while the selected audio device is TV Speakers?).  I'd expect the optical port to output nothing unless Optical is explicitly selected as the output.

Even more confusingly, the same thing holds true of the HDMI3(eARC) port: even when you have not attached an eARC device to HDMI3(eARC) or the TV has (for whatever reason) failed to recognize that an eARC device has been attached and neglected to automatically override the output device to HDMI-eARC, the port will still always send audio in whatever format is being used for the selected output.  This behavior is definitely buggy; some ARC or eARC devices will try to play that audio despite no eARC connection having been correctly established, which can lead to all kinds of user confusion and frustration (e.g. Why can't I select Pass-through even though I have an eARC device attached?).  I'd expect the HDMI3(eARC) port to output no audio unless an eARC device has been detected and initialized correctly by the TV and the selected audio output is HDMI-eARC.

> to get AC3 over optical you have to enable eARC in the settings

Not true. I get DD 5.1 (although very lagged) over the TV’s optical port just by setting the audio output to Optical.

Optical has absolutely nothing to do with eARC -- it's not even possible to select (or see) HDMI-eARC as an available audio output without an eARC device attached to HDMI3(eARC) and successfully recognized (initial eARC handshake) by the TV.

> does connecting an eARC device (like the Thenaudio) un-gray out the Pass-Through option

Yes, because Pass-through is only supported over eARC.  This TV does not support pass-through of audio over the optical port, by design.

> if so, when you select that can you also use the TV speakers?

No.  The entire point of Pass-through is that the audio is not decoded or processed by the TV in any way — not even to play through its own speakers.

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keithfkelly
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This has been quite the learning misadventure for me over the last few weeks.  Here's everything I've finally figured out.

Any audio decoding/conversion/processing by the TV introduces massive audio lag, and that's likely due to lack of sufficient computing horsepower inside the TV, so it's unlikely to be fixed by any firmware update.

The magic feature you need to enable and use is Pass-through mode (as opposed to PCM or Bitstream).  Sadly, these TVs are not spec'd to pass-through audio over the optical port; the best they can do is decode-and-reencode the audio to produce it on the optical output.  To achieve Pass-through mode, you must use eARC -- but very few customers at this time have sound bars or AV receivers that support eARC.  Most of us have devices that only support the older (and incompatible) ARC protocol, or that only support non-eARC HDMI or digital optical inputs.

The only solutions to this predicament are:

  1. Use optical out directly from the device (game console, PC, whatever) directly into the sound bar or AV receiver (thus bypassing the TV entirely).

  2. Use an AV receiver (with built-in eARC support) connected to HDMI3(eARC), with the TV set to use HDMI-eARC audio output in Pass-through mode, with the source device set to output whatever format your sound bar or AV receiver best knows how to decode.

  3. Use a ThenAudio SHARC as an eARC audio device connected to HDMI3(eARC), with the TV set to use HDMI-eARC audio output in Pass-through mode, with the source device set to output whatever format your sound bar or AV receiver best knows how to decode.  The SHARC provides multiple non-eARC output options (optical, HDMI, analog RCA) that you can feed into almost any old sound bar or AV receiver -- and it converts so quickly that no audio lag or lip-sync problems can be observed.  I now own a ThenAudio SHARC and can confirm it works perfectly with my Q90T to finally provide lag-free surround sound (including DD 5.1 and LPCM 7.1) to my old Yamaha AV receiver (which supports neither eARC nor Atmos).

One other IMPORTANT CATCH to be aware of:

The TV utterly relies upon HDMI pins 13 (CEC), 15 (DDC clock),  16 (DDC data), and 19 (hotplug detect) to detect and initialize any eARC audio device... but some devices are poorly-behaved and erroneously hard-wire one or more of these HDMI pins to ground (especially when the device is turned off).  If such a device is wired into your system anywhere -- even into a separate input port on the TV or AV receiver, or even into an HDMI switch in the signal path before the TV -- then the TV will fail to pop up its little "audio device detected" text or to show HDMI-eARC as an available audio output device in its menus.  If you plug in a SHARC or other eARC device and the TV doesn't obviously detect it, then you may still hear audio out over the eARC device, but the TV will not show HDMI-eARC as the audio output device, nor will it allow you to select the oh-so-critical Pass-through option in its menu.

If you find yourself in this situation, you must use process of elimination to identify the problematic HDMI device(s) in your system:

  1. Unplug ALL other HDMI devices from your system.
  2. Unplug and re-plug the eARC device into HDMI3(eARC).
  3. Wait several seconds to ensure the TV says it has detected the device.
    • If not, and you have no other HDMI devices attached to your system, then your eARC device does not actually support eARC, or is mis-configured, or is defective.
    • If not, and you have already successfully re-plugged other HDMI devices while going through previous iterations of this loop, then you have just found the problematic device.  You will need to leave this device unplugged from HDMI whenever it is not in use.
  4. Add back one more HDMI device, and go back to step 2.
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