Sky Stream Audio Settings -Passthrough option

[Barrowboy63]

Hi there, first time post and new Sky Stream user here. 
Slowly getting used to Stream, but one thing that's bugging me is lip sync. Having searched these forums I see I'm not alone, which is both comforting (that it's not just me) and disappointing (that Sky don't seem to have fixed the problem) 

My set up is Sky Stream connected by HDMI to Panasonic OLED which in turn is connected by HDMI ARC to a Panasonic Soundbar. I've tried all the differing options on the Stream box with varying results. In general, selecting PCM stereo seems the most stable but even that drifts out when streaming from some apps. I understand that Auto should give the best sound depending on source, and that Dolby Digital Plus and Dolby Digital 'force' the box to output audio in those formats (have I got that right?) But I don't understand what the 'Passthrough' option does. Can anyone enlighten me? 

[CoffeeDrinker]

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@Barrowboy63 wrote:

Hi there, first time post and new Sky Stream user here. 
Slowly getting used to Stream, but one thing that's bugging me is lip sync. Having searched these forums I see I'm not alone, which is both comforting (that it's not just me) and disappointing (that Sky don't seem to have fixed the problem) 

My set up is Sky Stream connected by HDMI to Panasonic OLED which in turn is connected by HDMI ARC to a Panasonic Soundbar. I've tried all the differing options on the Stream box with varying results. In general, selecting PCM stereo seems the most stable but even that drifts out when streaming from some apps. I understand that Auto should give the best sound depending on source, and that Dolby Digital Plus and Dolby Digital 'force' the box to output audio in those formats (have I got that right?) But I don't understand what the 'Passthrough' option does. Can anyone enlighten me? 

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Pass through forces the the audio 'bitstream' to be output for external decoding, without decoding it first. PCM Stereo decodes the audio bitstream in the Glass/Stream puck, downmixes it to stereo and outputs it for external amplification. DD+ outputs a DD+ bitstream for external decoding, DD outputs the older Dolby Digital standard for external decoding (for older AV amplifiers, soundbars and TVs that do not support the newer DD+ codec/standard).

Auto will attempt to discover what audio capability/capabilities the attached TV/AV receiver/soundbar supports and then send it the 'highest' standard it supports.

PCM stereo is the oldest and probably most widely supported by TVs etc, DD is next and can support 2.0 (stereo ) and 5.1. DD+ is newest and can support stereo, 5.1, 7.1 and Atmos but is the least widely supported.

[Barrowboy63]

@CoffeeDrinker  thank you for taking the time to explain the options in such detail and clarity. If I've understood you correctly, then passthrough on the Sky Stream box might be the best option for me, allowing the tv to decode the audio and passing it on to the Soundbar. I'll experiment and see how it goes. Once again, thank you for your time. 

[CoffeeDrinker]

@Barrowboy63 Glad to have helped - let us know how you get on.

I'm using a reasonably good Atmos AV receiver and 5.1.2 speaker system. Using pass through to ensure my receiver is doing all the decoding processing. Films soundtracks on Sky Cinema sound great, ditto the Atmos soundtracks on the likes of The Last Of Us & Game Of Thrones.

[Barrowboy63]

@CoffeeDrinker  will do. I've left it on passthrough connected via HDMI arc from the tv to the Soundbar and it seems good so far.  It's also got Atmos but the tv won't pass on the Atmos signal. But the Soundbar does have two HDMI inputs so I might experiment, but the downside to that is that the Soundbar won't pass through Dolby Vision. Can't have everything I guess🙂

[Rydell]

I have had this problem and last resort was to up grade my Sonos Beam gen 1 to the newer version gen 2. With the gen 1 there was no way to get correct lip sync to TV pass through to the sound bar but since I upgraded the Beam to gen 2 it's perfect. Perfect lip sync from Sky Stream puck.

[Nigelb1972]

ARC has been superseded by eARC and is the better for it as it supports higher bandwidth and part of the eARC protocol is that Audio has to stay in sync with Video... I'd say that's the perfect excuse to upgrade 😆

[trevforum]

HDMI 2.1 is supposed to have mandatory lipsync but all devices in the chain have to be 2.1 compliant.  I run my Sky Stream puck through a Pioneer receiver and use auto which transcodes DD+ to PCM Multichannel like the Apple TV does.  Setting to DD+ gave lipsync problems.  The preferred connection is to connect the puck to the reciever/ soundbar and then onto the TV.   

[Nigelb1972]

HDMI 2.1 has a higher bandwidth but it's eARC that had the protocols for Audio/Video sync 

[trevforum]

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@Nigelb1972 wrote:

HDMI 2.1 has a higher bandwidth but it's eARC that had the protocols for Audio/Video sync 

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Yes, but the lip sync protocol is not mandatory.

[Nigelb1972]

It is part of the protocol so if you're connected up properly with compatible kit, you shouldn't have any lip sync issues 

[RichTBiscuit]

Just wanted to add to this discussion, as ive hopefully worked through my issues with a Stream box activated last week. 

Set up is a Samsung Q70R TV with a Bose Smart Soundbar 600. Stream connected to TV with HDMI 2.1 cable (purchased to replace 2.0 as part of the process) and Soundbar connected to TV through HDMI Arc with 2.1 cable. 

The way ive got it to 1.) Stop cutting out for 1-2secs during Atmos programming and 2.) Correct Lip Sync is to set the Stream to Passthrough, the TV to Dolby Digital Plus and NOT select the Atmos button. This seems to have corrected Lip Sync (i have a 40ms delay set to the soundbar but this works across the stream and TV apps) and the other issue when i watched the football last night. 

In essence, it seems the trick is not to allow the Stream box or the TV to decode the Atmos signal. Letting the soundbar do its job seems to be the answer, and although Atmos is deselected on the TV i think this refers to the processing element as the soundbar still outputs an Atmos signal. 

My TV is Arc, not EArc so this was my last attempt before biting the bullet and upgrading so i can use the EArc protocol. Hope this helps anyone in a similar situation, but i presume EArc is the way to easily resolve if available.