Surprised & puzzled - DTS converts to Dolby Digital 5.1 in my Beam setup!

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It’s well known in these circles that the Beam, Playbar and Playbase won’t play DTS soundtracks, and the best we can hope for in this situation is a down-mixed stereo output.  I’ve also read that Blu-ray players that convert DTS to DD on the fly are like hens teeth - the lists I’ve seen a contain a few Samsung and Oppo players only.

So, how come I’m getting DD5.1 out of my Beam (reported by the app, and by my ears) from plain DTS and DTS-HD Master Audio soundtracks?

My setup is:

  • Sony UBP-M800 Mk2 UHD bluray player
  • Sony AG9 TV
  • Beam connected via the TV’s eARC connection
  • Sub and Play:1 rears bonded to Beam

There’s no fancy trickery or other boxes, switches, etc.  It’s simply bluray player to TV to Beam, all via HDMI.

To get sound from the Beam, I had to make one change to the M800’s audio settings:  “Digital Audio Output” = PCM.  The other option (“Auto” = bitstream in most cases I believe) gives silence.  All other audio settings on the player (and there aren’t many) are at the default.  None of them appear to relate to transcoding audio formats.

The result, as reported from the player’s display and by the Sonos app:

  • DVD or BluRay soundtrack:  DTS-HD Master Audio 5.1 48kHz, or DTS 5.1 48kHx
  • Blu-ray player output via HDMI = “LPCM 5.1Ch 48kHz”
  • Sonos app reports Beam is receiving “Dolby Digital 5.1”

What’s going on here?  I’ve tested this on several discs, 4K and standard bluray, with the same results.

Have I misunderstood the problem everyone else is talking about?  Or have I struck lucky with the Sony M800 Mk2?

18 replies

Userlevel 7

You answered your own question the Sony is converting the stream to PCM which the Beam can handle over HDMI. The problem would be over optical.

It’s a function of HDMI CEC. The Sonos reports two things to the hub, your TV, one is that it is a speaker, and the other that it handles two codecs, stereo and Dolby Digital. The HDMI CEC hub in the TV then sends the acceptable codecs to all source devices. Assuming the source device is HDMI CEC compliant, it then adjusts itself to only send a Dolby Digital or stereo signal along to the hub, which then forwards that to the speaker. 

There are some devices that can accept an HDMI CEC command even when the option isn’t available in the options shown to the user in the audio settings for the device. 

Unfortunately, there are some hubs (TVs) and sources that either didn’t properly implement HDMI CEC, at least in the first attempt, which is why you frequently see suggestions for people to download new software for the TV, as well as a reboot process in case something has gone awry. Unfortunately, chances of software updates tend to be slimmer on source devices, but these updates should be applied where possible.

Unfortunately, it’s frequently the receiver/speaker that gets the blame, when it is most often something upstream. To my knowledge, to date, Sonos has not needed to update their relatively tangential implementation of HDMI CEC. It has almost always been an implementation issue in the HDMI CEC hub, built in to the TV set. There have been a handful of issues with source devices, but since that’s significantly upstream from the Sonos, it’s really much harder to define from the end point, the Sonos. 

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Thanks both of you.   So, I think you’re saying that my player, the Sony UBP-X800 Mk2, converts DTS to Dolby Digital on the fly?  If so, this is good news, and I will share this news with others via the BD Players thread. 

I appreciate that the player’s ability to do this is only one (necessary) link in the chain, and that as you say, Bruce, the Sony’s HDMI-CEC (aka Bravia Link) implementation ensures that the Beam’s desire for DD 5.1 reaches the player. 

No, I wouldn’t expect this is on the fly conversion, I would think the HDMI CEC link is telling the player to only play the Dolby Digital track. But that’s a guess, you’d need to check with the folks at Sony for more clarity. On the fly conversion is a whole different set of electronic circuitry of some cost, and is rather unlikely to be included in the player, without heralding it and using it as a marketing point. 

There would be a way to test this, with relatively little complexity. Find. Blu-ray Disc that does not have a Dolby Digital track, only stereo and DTS and play that. See what shows up in the controller for your Beam. If it’s stereo, then your Blu-ray isn’t doing on the fly translation. If it’s Dolby Digital, then it is doing the magical translation,  and I need to go buy one. ;) 

Or possibly, the TV is doing the translation, since it’s in the stream. Unlikely, but not impossible. 

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Sorry, I didn’t make that point clear in my original post:  all of my test discs had NO Dolby Digital English language soundtracks on them (and that includes DD5.1, True HD, Atmos, etc).  If they had, I would have selected one of those soundtracks from the disc menu and would never have discovered my surprising finding! :wink:   And my French, German, Potuguese and Catalan etc isn’t good enough to watch in any other language than English.   So I select the DTS tracks from the disc menu, and it plays as DD5.1 on the Beam, just so long as I set Digital Audio Output = PCM on the BD player.  Magic!

Regarding the TV, I haven’t seen anything in the manual or settings menus to suggest it’s doing any sort of audio conversion.  But someone might know different?


BTW, I got the BD player model name wrong in my first post:  its the Sony UBP-X800 M2 (as in Mark 2; I’ve seen others with the original X800 complaining of no joy with DTS...) 


That is indeed magic!

Now I need to go price the UBP-X800 M2. Thanks for sharing!

You can verify the audio format that SONOS is receiving by going to Settings → System → About My System

Userlevel 4
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Hi Buzz, you’re right, I did that as per my original post:

  • Sonos app reports Beam is receiving “Dolby Digital 5.1”
Userlevel 4
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Bruce: I paid £265 for it in the UK. It’s a great player - superb picture and they seem to have ironed out some quirks/issues from the Mak 1 version. Very limited on streaming apps and other bells and whistles, and some won’t like the minimalist styling and lack of a display, but I love it. Super quiet too, even with 4K discs. 

Hi, did you try to connect the BD player HDMI audio output directly to the Beam ?

Just to be sure the TV is not doing anything in your setup 

Curious that a player configured to send PCM decides actually to use DD

Maybe you can although try to disconnect the Beam and see what signal is sent to the TV, 



My best guess… BRP is outputting PCM 5.1 and TV is transcoding to DD5.1.

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This would be very good news!

This would be very good news!

Yes, if you have that BRP and TV.  And if I am correct,  which  is far from certain. 

A couple of years ago I stopped buying discs, in favor of my Apple TV. That may change, if this device does what it seems to. It’s at Amazon for $248 here in the US. 

But I’m going to hold off until I get the Arc at the earliest, and see how things stand. Changing back from one format to another is a pretty big change, and I’ve gotten used to not having physical media. 

Userlevel 2

I had the same issue on my LG C9. Had to enable PCM for DTS. Dolby Digital discs played with no issue under bitstream. I have a Panasonic DP-UB820. Glad I got it working but it’s clearly a codec support issue with Sonos. For the premium, DTS could be supported too. 

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@alexfirth91 Did you get surround sound or just stereo?

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I only tried one film, but Jojo Rabbit worked in 5.1 surround DTS as selected. When I first tried I heard nothing, but the fix I did worked.