Sonos Arc loud pop then audio loss

I really don’t quite understand the insistence by @ken_griffiths that this is making a claim that the Arc does not support Atmos is a “non-starter.”

There are three mechanisms for delivering Atmos content, as I understanding it, (1) DD+, (2) Dolby TrueHD, and (3) Dolby MAT. I don’t see any reason to disagree with your assertion that DD+ and Dolby TrueHD formats are performing as expected on the Arc. However, it seems incredibly clear at this point that the Arc is unable to correctly decode/handle Dolby MAT formats - which is used by Apple TV and the XBox. Based on your post history, you have not experienced these issues because you are not using a streaming device that outputs in the Dolby MAT format. That’s great for you - but it doesn't address the ongoing issue that many other Arc owners still face.

And in fact, Sonos staff themselves explains here OVER THREE YEARS AGO that Arc is *supposed* to support all three formats of Dolby Atmos – via DD+, TrueHD, and Dolby MAT. What I think is clear at this point is that the Arc is unable to deliver Atmos content via Dolby MAT format, which is why we are seeing issue with the Apple TV and Xbox, which use those formats. We understand that you haven’t had an issue with your devices - but you can’t really comment on the horrible experience of those using mainstream devices delivering one of other MAIN types of Atmos content delivery. 

You reference the footnote on the home theater audio formats page, but it’s honestly kind of unintelligible to me (and not really clear what it’s trying to say - is it supposed to be a disclaimer?). It mentions Dolby MAT but doesn’t really comment on the implications (if any) of this format - why is it even on this page if there isn’t further clarification regarding why this distinction is even being highlighted?

And to be honest, the lay user of home electronics should not have to spend hours reading about Atmos delivery formats to understand why their device isn’t working. If you are going to advertise the Arc as being Atmos-capable (and talk in your forums about how it supports all Atmos delivery formats and codecs), then it needs to work for people using the device with two of the most common streaming devices that exist. The sound it makes really, truly sounds like a gunshot - it wakes my family from the other side of the house.

As @KrylonBlue stated quite well: 

Sonos released a product that isn’t capable of handling a format of Atmos that is used by two or more of the largest devices on the market. We’re not talking about some off the wall streaming box but rather an Xbox and Apple TV. If Sonos is going to sell an Atmos enabled product they must work as an Atmos enabled product as a whole. 

More importantly, we shouldn’t even BE in the position of wildly speculating about what is causing the issue, because at the end of the day, this is an issue impacting MANY Sonos customers, and it has been largely radio silence from the company regarding what has actually been done to troubleshoot the issue. If someone from Sonos could actually provide specific information about exactly what has been done from an engineering perspective, maybe we wouldn’t have a thread with 870+ responses trying to figure out why this issue persists. What does happen with all those diagnostics we submit, after all? As @blunderdome and others have said:

You know this is almost more frustrating to hear than just radio silence.  Two years into this thread and “We’re aware of the issue and are looking into it” simply isn’t good enough.

We are three years into this issue. It’s well known and documented. Videos have been uploaded. The issue is reproducible easily for those with the affected streaming devices. Removing the TV from the equation with devices such as Arcane also hasn’t solved the issue. Nor has disabling functions such as CEC. It’s not like Sonos is a low-budget brand - people have spent thousands of dollars for their systems, and really, if you are advertising Sonos Atmos compatibility, it should work with one of the most widely used streaming devices in the world. 

Continued apathy towards this issue really isn’t acceptable. I’m at the point where I would favor drafting a letter to the company and welcoming signers. It should get the attention of Ars Technica, Rtings, and other organizations in the tech/audio community - I’m more frustrated now out of principal. It would be one thing if they were more publicly responsive to the issue and demonstrating clear and well-articulated efforts to troubleshoot the issue rather than generic platitudes, but frankly, at this point it’s unacceptable. 

It strikes me that if it is the case that the LPCM (Atmos) Audio is being sent by Apple and Microsoft devices as ‘Multichannel PCM Audio’ and ‘Atmos Object Metadata’ and that these two things are ‘perhaps’ arriving at their destination out of sync, then that’s not actually a Sonos issue - whether they should publicly comment about the quality of another partners data quality is another matter, plus it might even be something en-route between devices that’s causing the sync issue.

Either way, it seems everyone wants Sonos to pick up the mess and sort it and I’m not personally sure the ball should be in their court to do that.

All this of course is speculation anyway and based on an interpretation of the AI response to my question and I’ve no way personally of corroborating it. If anyone should comment on the matter though, I would have thought it should be Apple, or Microsoft, as they are the originator/owner of the data.

In my view, it’s also a pity Apple and Microsoft do not offer an alternative to their customers and allow them to use other codecs …Dolby TrueHD and/or DD Plus …as those codecs appear to be working in every other situation, whereas their current audio delivery method seems to not be working as it should be, if of course, the above thoughts are correct.

Anyway, my answer would be ‘No’ I do not think Sonos should comment on the quality of partner data in public, the owner of the data is the one that should comment and it is for them to research and find out why their own data is arriving at the intended destination out of sync. I would just expect Sonos to assist those other companies in their research, without publicly commenting. 

@Ken_Griffiths , I’m not saying that Sonos should cast aspersions against Apple and Microsoft. Clearly what I wrote wouldn’t be a corporate response! ”They should feel bad.” Lol. 
 

Im saying that Sonos ought to disclaim that there may be a compatibility issue with Apple TV and Xbox. Do you really think customer do not deserve a heads up? Is it preferable that they spend thousands on a Sonos system, find out afterwards they can’t use Atmos with Apple TV or Xbox, potentially after being out of the return window?

I can perhaps only very briefly reiterate what Sonos Staff have mentioned already on this topic …that the matter is being investigated ..and my own understanding is that in the meantime, the Sonos Staff here have advised users to switch off Atmos when using McPCM. Clearly that’s just in these circumstances only and the other forms of Atmos (Dolby TrueHD/DD+ codecs) are still working perfectly fine. McPCM 5.1 surround audio is also working fine too, originating from the devices mentioned (as, unlike McPCM Atmos, that audio format does not require the object metadata).

I’m not sure that Sonos can add anything further to what they’ve already said. Unless something new perhaps comes to light.

If ‘other’ companies are still investigating, then I guess Sonos are having to wait too, along with the rest of us.

Please note @ProfessorFrag all I’m doing here is speculating (based on the AI response) as to the possible reasons why there maybe an issue with the ‘McPCM Atmos’ format and that the heart of the issue ‘might’ be that the Atmos Object Metadata is arriving at the destination out of sync with the McPCM audio, causing the ‘pop’ noise.

Maybe when the investigation is complete we may all discover the actual reasons behind this and why it’s proving so difficult to fix. For now though we can each only speculate about these things. 

@Ken_Griffiths do you think Sonos should disclaim this issue before customers make a purchase?

Not specifically ‘no’ and my own reasons for saying that, is because generally speaking, manufactures normally only state what their products do support in their marketing literature and not what they don’t support, (otherwise that would be quite an exhaustive list in some cases). Sonos do not disclaim that they do not support DTS:X audio, or various other codecs, for example. It would seem odd to disclaim just this one specific issue and, of course, it appears the matter is still being investigated anyway at the moment.

Sonos Staff have advised users here in the community that they should use LPCM 5.1 surround audio from these 3rd-party devices instead, whilst the matter is being investigated.
 

@ProfessorFrag,

I did just go back to the earlier mentioned Sonos link here, just to check… 

https://support.sonos.com/en-us/article/supported-home-theater-audio-formats

.. and Sonos are not exactly pushing support for "McPCM Atmos” codec in their literature. It (Dolby MAT) is not in that list of codecs, other than perhaps it forms part of the term ‘Dolby Atmos’, but in fairness, I haven’t checked every aspect of their ‘official’ marketing material. 

I can’t believe after 2 years Sonos still hasn’t fixed this. I literally forgot about it because I usually don’t use my Appletv. I was watching an atmos movies and literally 10 seconds into it the loud POP OF DEATH and arc is done. I was reminded about how stupid the Sonos arc is. I usually just use my apps on the tv and not appletv and forgot. I’ve also never once in my life hear a single sound come out of the up firing speakers on the arc ever. Even when watching in atmos movie with them turned up full blast. The ARC to me is pretty disappointing to say the least and the lack on someone that actually works at Sonos to have a real answers is embarrassing. 

So, I’m going to take a shot at summarizing my take on the issue after extensive reading and building on the excellent troubleshooting work by others in this thread.

The Xbox One X/S and ATV 4K use a Dolby MAT 2.0 encoder (metadata-enhanced audio transmission) to output sound – this process takes Dolby Digital Plus (DD+) or Dolby True HD Atmos bitstream and repackages it as LPCM output (linear pulse code modulation) with attached Dolby Atmos metadata. Think of it as LPCM with attached Atmos data. This Dolby MAT output is sent via HDMI to a receiver or soundbar that has a built-in decoder (in this case, the Sonos Arc and Beam). Per Dolby, the final device in the pass-through chain must have a decoder capable of processing the Dolby MAT format. As described by AV Pro Edge:

Within the MAT encode process, the bitstreams are encoded into encapsulated MAT frames, converted to LPCM and ferried over HDMI 1.3 or later using a fixed bit-rate, into a compatible AVR/processor with a Dolby MAT decoder that unpacks and converts the MAT frames into the original Dolby bitstreams. Apple TV as of tvOS 16.2 does NOT support pass-through bit streams. Atmos is sent as Dolby Metadata-enhanced Audio Transmission (Dolby MAT) via LPCM. If Dolby Atmos is off the E-AC-3 audio is sent without metadata.

This is why you will typically see LPCM (or “Dolby Atmos”) as the output type in the Sonos app when streaming Atmos content via Apple TV or Xbox – by definition, Dolby MAT 2.0 involves conversion into LPCM + Atmos metadata by the encoding device. As Dolby itself details:

With the introduction of Dolby Atmos, we have expanded the Dolby MAT technology to support encoding and decoding of Dolby Atmos metadata incorporated in lossless pulse-code modulation (PCM) audio. A key benefit of Dolby MAT 2.0 is that Dolby Atmos object-based audio can be dynamically encoded in real time and transmitted from a source device with limited latency and processing complexity. Likely sources that will employ Dolby MAT encoding include broadcast set-top boxes and game consoles. The Dolby MAT 2.0 decoder outputs the object-based audio and its metadata for further processing inside the device.

Sonos explicitly advertises support for this format; their various descriptions of the audio formats are a little muddled, to be honest, with some redundancy in terminology. But they clearly outline support for Dolby Atmos in the form of Dolby Multichannel PCM with Atmos object data delivered via MAT. This is the exact format used by Xbox and Apple TV. You can see a detailed discussion of this here by a staff member that explained these nuances when the Arc was initially released: “Arc-compatible codecs that contain Dolby Atmos include Dolby Digital Plus, Dolby TrueHD, and Dolby MAT.” I think there are a few minor errors in this explanation in that Dolby MAT isn’t exactly a codec per se – rather, as AV Pro Edge explains:

Dolby MAT is neither a codec nor a format. While Dolby MAT utilizes an encode/decode algorithm, it is constrained within a closed environment, devoid a final analog stage. Dolby MAT might be defined as an encode/conversion/transport/conversion/decode process, a “bridge” created between compatible Dolby MAT devices for any of the three codecs Dolby has designated to deliver Dolby Atmos content to the home, Dolby Digital Plus/JOC, Dolby TrueHD, and with ATSC 3.0 tuners, Dolby AC-4. Dolby MAT takes advantage of the high-capacity lanes provided by the eight, 16bit, 192kHz audio carrier lanes in the HDMI standard, starting with HDMI 1.3, and aggregates the bandwidth of multiple lanes to establish a data transport layer.

Based on the multitude of comments and complaints both on the Sonos forum and other sites, it seems very clear that the popping, gunshot-esque banging sound, and audio dropouts are almost certainly isolated to Atmos content delivered via Dolby MAT 2.0 encode/decode process. This also explains why these issues are isolated to streaming devices that utilize this format (Xbox and ATV).

I am open to the idea that this could be related to an issue on the encoding side (ie Xbox or Apple TV) of the MAT 2.0 container. However, the fact that devices produced by two different companies (Microsoft and Apple) that encode using the MAT 2.0 format both produce issues with sound delivery on the Arc leads one to believe that this is an issue on the decoding (Sonos) side. If Sonos advertises compatibility with MAT 2.0 Atmos (LPCM + Atmos data), I am curious what output device they used to even test that compatibility in the first place. Given that Xbox and ATV are the main devices using this encoding process, it would seem odd to brand the device as “compatible” without testing the only two known streaming boxes that use the format? Dolby also anticipates more devices will start using MAT over the coming years, as well. Further, Sonos continues to advertise compatibility over three years into a widely known issue. Sonos support recommends turning off Atmos in the ATV to solve the issue – this obviously works (as it has for me) because it removes the aforementioned problems from the equation at the expense of Atmos functionality. Further, there are also numerous examples by people out there with receivers and sound bars that work perfectly fine with streamers that re-encode to an uncompressed multichannel LPCM with Dolby MAT 2.0 stream, which seems to suggest that there are hardware and software differences in the decoding devices (receiver/soundbar) that significantly impact the ability to deliver this content effectively.

As I’ve stated before, we wouldn’t be in a position of speculating if Sonos commented more meaningfully on the problem. Responses over the last THREE YEARS have been non-specific, devoid of technical details, and absent any accountability for moving the issue forward. I was told that this was an “extremely transient, low-probability phenomenon.” I strongly disagree – I think this is simply a reflection of the reality that, more commonly, users of the Arc do not have the required audio set up (ATV/Xbox + top-tier streaming subscription with Atmos content + Atmos-recorded content + TV with eARC and appropriate pass-through) to produce the issue. It doesn’t mean the issue isn’t persistent and affecting thousands of users. In fact, as the volume of Atmos-enabled content on streaming services such as Netflix, Amazon, and Apple TV+ increases and more people upgrade to newer TV sets with eARC and Atmos passthrough compatibility, the issue will likely become even more common. As anyone here who is impacted knows, reproducing it is not challenging – just fire up some Atmos content on the Apple TV and you can expect to hear a gunshot sound followed by audio loss within the first 5-10 minutes. I’m happy to have a Sonos technician come to my house (or send in my equipment) if reproducibility is the concern here – they have not taken me up on this offer. Bottom line, the ideal solution is for Apple/Microsoft to provide an option to bitstream DD+ and TrueHD with Atmos natively via passthrough – but my main complaint with Sonos is advertising compatibility with MAT Atmos delivery and doing little to address the concerns of a loyal (though less so with this behavior) fan base.

If Sonos strongly believes this is an upstream issue with the ATV/Xbox encoding/timing process, it would even be helpful to be presented with technical information to support this. It would allow those affected to take this information to Apple, Microsoft, and Dolby developers to further narrow down the problem. And if this is the case, there should also be a disclaimer that Arc and Beam do not currently support any Dolby MAT 2.0 streaming devices actively on the market. But here we are, three years in, with nearly zero helpful information from the engineering team.

To be honest, I am just really disheartened by the response from the Sonos team. I have been a loyal Sonos user for 7+ years and have spent thousands on Sonos products and recommended them to friends and family. The response has been nothing short of anemic. It’s true that many people with the Arc and Beam 2 are not affected by this issue – unless you are interfacing with Atmos content delivered via MAT, you probably are unlikely to ever experience this problem. But for those of us who are impacted, it is a huge issue. It makes Atmos unusable. I’d feel a heck of a lot better if there had been a meaningful, public response from the company addressing this issue – but here we are. I just don’t feel like I can recommend these products moving forward unless something changes.

I hope some of the recent activity in this thread serves as a call to action. If we do not get a more meaningful response from the company (@Corry P, please help!) over the next month, I aim to pursue other avenues for bringing attention to the issue more publicly and would welcome anyone who would like to contribute. I would like to give Sonos an opportunity to respond first, but I don’t have a lot of optimism based on this thread.  I’ll end by highlighting a few comments in this forum that summarize the frustration.

@Cavecanem  I have contacted in multiple times support via phone and email, with the same corporate response everyone here has experienced.

@mond0  Lurking this forum and reading all these stories of how Sonos support has been deflecting and gaslighting their customers for years has made me reconsider ever purchasing a Sonos product.

@Rios  As I’ve said before this is a Sonos hardware bug that can be recreated with the same parameters 100% of the time. Each time I read how we have to turn off the feature that we specifically paid for is infuriating.

@BobSmithHome  After reading almost all of this 2 year old thread, I’m shocked that Sonos is sending these out to unsuspecting customers with no warning or recommendations. If I had any faith that Sonos was really doing something, I’d keep it and wait for a fix. But it’s pretty clear after reading this thread that they’re just jerking us around. 

@Rowley_1  Beyond a joke, this is a company knowingly selling a product that has issues performing what it’s advertised to do to consumers without warning them. After the whole S1 to S2 forced obsolescence debacle, I should have learnt my lesson.

@Schlagdog I can’t believe after 2 years Sonos still hasn’t fixed this. I was watching an atmos movies and literally 10 seconds into it the loud POP OF DEATH and arc is done...The ARC to me is pretty disappointing to say the least and the lack on someone that actually works at Sonos to have a real answers is embarrassing. 

@blunderdome: You know this is almost more frustrating to hear than just radio silence.  Two years into this thread and “We’re aware of the issue and are looking into it” simply isn’t good enough.

Happy 900th post, thread!

@rc12 that is an amazing reference post. Thank you for the time and effort it must have taken to put it together.

I encourage everyone to link rc12’s post directly for anyone new to the Sonos Pop. Here is the direct link:

https://en.community.sonos.com/home-theater-229129/sonos-arc-loud-pop-then-audio-loss-6852340/index36.html?postid=16666333#post16666333