Dolby Atmos Support

[maletor]

I have been unable to get Dolby Atmos steams to work correctly with passthrough. There are reports that this works correctly on Kodi, so it must be possible.

Sample files can be found on a related ffmpeg bug report.

I have a receiver capable of Dolby Atmos and can test patches if you would like.

[kevmitch]

Which ao are you using?

What exactly happens when you try?

[maletor]

I am using ALSA.

I can enumerate truehd for passthrough, but technically this is Dolby Atmos. As one might expect, setting truehd only sends TrueHD as evidenced by the DOLBY ATMOS light not turning on.

A similar problem is likely to happen when DTS:X is released.

[ghost]

There are reports that this works correctly on Kodi, so it must be possible.

From what I can see in kodi code, their way to pack truehd into spdif is pretty similar to ffmpeg's (and we use ffmpeg's code). Could you try to capture the bytestream produced by both players? (I'm not totally sure how to do this. In mpv you can use --ao=pcm.)

[maletor]

@wm4, I think we can get this to work with something like ffmpeg -i INPUT -f alsa default. If that's the case is there much complexity with supporting that in mpv?

This may not be working now because --audio-spdif=help does not list any kind of "raw" format?

[ghost]

Doesn't this command just decode to pcm?

[maletor]

You're right. It decodes, in this case, from TrueHD to PCM. There's got to be a way to stream the bits directly to the hardware, unmolested.

[maletor]

Tried aplay -Ddefault ~/Atmos.proprietary with no luck. The issue is ALSA thinks the sample rate must be set, which doesn't even make sense as a requirement to stream bits and certainly doesn't make sense for "object based sound", So, I try iecset -Ddefault audio 0 but still no luck. If one could read the Kodi code to know what it's doing that would be the most helpful to resolve.

[ghost]

which doesn't even make sense as a requirement to stream bits

Actually it does. Compressed passthrough is a hack that transfers the data pretending it's some form of pcm. This happens on all level, even the lowest.

[ghost]

Also, does this definitely work with kodi? Did you try it?

[goblin]

evidenced by the DOLBY ATMOS light not turning on

@maletor which hardware has this light? I find it extremely hard to find; for instance, the top-end Samsung HW-N950 doesn't seem to have any way to distinguish between EAC3 (DD+), TrueHD, or either of these with the extra Atmos metadata.

I'm starting to think Dolby Atmos (in case of this soundbar at least) is just a marketing gimmick to mean "we'll do some signal processing on your 5.1/7.1 (E)AC3/TrueHD streams and send it out some extra tweeters on the sides of the soundbar and don't you worry about any metadata in your source".

Also, how can one distinguish between a EAC3/TrueHD and Atmos streams programatically or on the command line? mpv seems to just display ac3 or truehd when playing the Amaze demo from https://thedigitaltheater.com/dolby-trailers/ (the "Lossless-ATMOS" one is described as "Dolby TrueHD 7.1 ATMOS"). Importing them in Audacity just gives you 6 or 8 regular channels. Is there a way to check if there's actually some extra metadata there (and what data that is)?

[Neustradamus]

Any news on it?

[ghost]

Stop falling for dolby marketing scams.

[Bitwolfies]

So does atmos work in mpv or not? I’m really confused here.

[tokyovigilante]

It does for my use (mpv build from master, correct passthrough flags set, HDMI to Denon AVR-3600H). Atmos indicator on receiver when appropriate EAC3 w/ embedded Atmos data tracks played. Some issues with sync loss on seek, although I note @wm4 has kindly patched some of the stream-silence behaviour recently.

[bombadilio]

I can get DOLBY atmos / DTS-HD tracks to play on MPC-BE x64 but in MPV it only shows up as Dolby Surround. Is there a work around for this?