FFMPEG now supports streaming Dolby Atmos from mkv to fMP4 HLS & it works natively on iOS

General Discussions
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ffmpeg has been updated (in June 2025) to preserve Dolby Atmos when remuxing from mkv to fmp4 (fragmented mp4) with HLS

What this means: when watching an mkv (hevc+atmos) from PC server on iOS using Jellyfin (with native avplayer enabled), I get full atmos (instead of the usual multichannel)

This is probably also how Infuse works behind the scenes

Please can Plex also implement mkv to fMP4/HLS to iOS native avplayer (as a beta or advanced option at least)

Plex with old (avplayer) enabled already supports atmos when playing mp4 files, now is the time bring this support to mkv as well via the updated ffmpeg.

Jellyfin and Infuse both support this. Time for Plex to catch up.

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That’s a nice feature update!

Plex will probably implement it sometime in the future as they are just now rebuilding their custom FFMPEG starting with 6.1 branch:

One of the stated goals is to make it easier to upgrade\release.

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We have to be VERY careful with anything dolby related, however this is worth a discussion with legal once we eventually update to a version containing this feature.

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Really looking forward to this. It will be an absolute game changer for Apple users.

I can already play Dolby Vision videos directly from inside mkv but the Dolby Atmos audio track falls back to the multichannel base layer.

Below is a screenshot showing Plex playing Dolby Vision and Dolby Atmos on my Apple TV (with a manually remuxed mkv using the updated ffmpeg).

Plex should automatically switch to remux + Apple’s native AVPlayer when it encounters Dolby Atmos (like it currently does when it encounters Dolby Vision)

Edit: could you also add an option to stop transcoding videos when only tone mapping is required as AVPlayer automatically does this when needed.

Thanks for taking the time to reply!

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The new plex app doesn’t even give you the option to use the native player. On iOS 26, using the native player is also very buggy causing out of sync audio.

I just tried this using Emby and Atmos played back fine. This is strange because emby is using an ffmpeg version from 2017 yet it works. Does not work with Plex though.

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Last I’d heard, Emby was just using whatever implementation ffmpeg had for Dolby codecs. Plex licenses codecs from Dolby, which means they cannot use what’s in ffmpeg, and have to do things a certain way that adheres to Dolby’s license restrictions, and passes regular auditing.

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This has nothing to do with licensing. All ffmpeg is doing here is unpacking the streams from the mkv container and repackaging them as fmp4.

The actual decoding is done by Apple’s avplayer (and Apple has the license to decode Atmos). Plex is simply passing whatever compatible media the user gives it to Apple’s built in player.

It’s not any different on Android where Plex lets the platform decode Dolby (via exoplayer using the TV manufacturer’s licensed decoders).

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Plex should already support fMP4, it did in the older iOS/tvOS Plex app. From memory, it was something we had to do for Dolby Vision to work properly. :thinking:

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You are correct, but up until now, ffmpeg has been destroying the Atmos metadata in the process.

Atmos tracks were playing as generic multichannel without the Atmos effects.

Upstream ffmpeg have finally fixed this so now the streams will be copied correctly and TVs will show the atmos logo.

Can’t wait until this makes it to stable Plex

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i’m gonna guess you will be waiting a looooong time given how plex only adds features that might make them money, not features users actually want. They are a business, and making money is why they exist.