Dolby TrueHD/Atmos Support on LG C8

[Paul77nz 8]

@@Luke

 

I have many 4K HDR videos (MPEG-H/HEVC/h.265) which have Dolby Atmos as the default audio track. When I try to play them with the Dolby Atmos audio track selected on my LG OLED C8 (Emby app version 1.0.9), Emby does a full transcode of both audio and video.

 

If I play the same file with a Dolby Digital, Dolby Digital +, DTS, or DTS-MA audio track it direct plays.

 

But here's the thing... if I play the same file with the Atmos track using the LG C8's built-in media player, it plays the file with full HDR video and full audio (it briefly displays a message that says "This video does not support audio", however the sound does play with no problems). The audio is sent to my amp from the TV via ARC - the amp reports Dolby Digital rather than Atmos, but that is presumably the TV downsampling it since full Atmos can't pass over ARC.

 

I removed all audio tracks from the file except for the Atmos track to double check it wasn't just automatically selecting a compatible audio track - even when Atmos is the only audio track available it plays fine in the native player on the LG C8.

 

Why is Emby transcoding files with Atmos audio when it appears that the TV is actually perfectly capable of playing them natively?

 

Thanks for your help.

 

EDIT: I am running Emby Server for Windows version 3.5.3.0

Edited December 16, 2018 by Paul77nz

[Paul77nz 8]

Apologies @@Luke, I just checked the file and I had failed to remove the AC3 compatibility track. The native LG player must have been selecting that, because when I removed it and left only the Atmos the audio actually didn't work.

 

Still curious as to why Emby is doing a full transcode of the video and audio, and instead of only the audio?

 

Actually, now on my test file it is direct streaming the video and transcoding the only the audio, although what would be good was if would selected the AC3 compatibilty track as the default for devices that don't support Atmos playback, thus eliminate the need for any transcoding at all.

 

Thanks

Edited December 15, 2018 by Paul77nz

[Paul77nz 8]

@@Luke Upon further testing I am getting some really strange results. You can probably ignore most of the above and just read the below results:

 

Emby Windows Server 3.5.3.0, LG Emby app 1.0.9 on LG OLED C8.

 

If I start a video file with a standard Dolby Digital track selected and then change the track to Atmos (Dolby TrueHD 7.1) during playback it keeps Direct Playing (see attached embyserver-Switch_from_DD_to_THD.txt).

 

If I start it with Atmos (Dolby TrueHD 7.1) already selected, it transcodes the audio and direct streams the video (see attached embyserver-THD.txt and ffmpeg-remux-THD.txt).

 

If I resume a video with Atmos (Dolby TrueHD 7.1) selected, it does a full transcode of both audio and video - which basically chokes my server (see attached embyserver-resume_THD.txt, ffmpeg-remux-resume_THD.txt, and ffmpeg-transcode-resume_THD_1.txt - ffmpeg-transcode-resume_THD_7.txt).

 

If I can start it with standard Dolby Digital then switch to Atmos (Dolby TrueHD 7.1) and have it carry on Direct Playing, surely I should be able to start or resume with Atmos (Dolby TrueHD 7.1) and also have it Direct Play?

 

Thanks

embyserver-Switch_from_DD_to_THD.txt

embyserver-THD.txt

ffmpeg-remux-THD.txt

embyserver-resume_THD.txt

ffmpeg-remux-resume_THD.txt

ffmpeg-transcode-resume_THD_1.txt

ffmpeg-transcode-resume_THD_2.txt

ffmpeg-transcode-resume_THD_3.txt

ffmpeg-transcode-resume_THD_4.txt

ffmpeg-transcode-resume_THD_5.txt

ffmpeg-transcode-resume_THD_6.txt

ffmpeg-transcode-resume_THD_7.txt

Edited December 16, 2018 by Paul77nz

[SamES 892]

There is an known issue with the current LG release. If you select a TrueHD track during playback, the track does not actually change, it continues with the previous track. That’s why it appears to Direct play. Selecting TrueHD from the details page will play the TrueHD track but with conversion.

 

In a future release the issue will be resolved so that selecting the TrueHD track during playback will select it but it will still convert the Audio track. Direct play of TrueHD is just not possible. As you discovered, even the native player will switch to an alternate track if there is one.

[Paul77nz 8]

There is an known issue with the current LG release. If you select a TrueHD track during playback, the track does not actually change, it continues with the previous track. That’s why it appears to Direct play. Selecting TrueHD from the details page will play the TrueHD track but with conversion.

 

In a future release the issue will be resolved so that selecting the TrueHD track during playback will select it but it will still convert the Audio track. Direct play of TrueHD is just not possible. As you discovered, even the native player will switch to an alternate track if there is one.

 

Thanks @@SamES that makes sense for why it appears to keep direct playing. However it doesn't explain why when I resume a video with the TrueHD track selected (rather than playing from the beginning) it does a full transcode of the video as well. Is this a known issue?

Edited December 16, 2018 by Paul77nz

[Luke 37132]

For the resume, it looks like it tried to direct play, and then the video player reported a problem and so the app automatically switched to transcoding.

[Paul77nz 8]

For the resume, it looks like it tried to direct play, and then the video player reported a problem and so the app automatically switched to transcoding.

@@Luke so is this a bug that will be looked at, since it shouldn't have been trying to direct play? I can reproduce this on multiple files.

 

Thanks

[Luke 37132]

It successfully played, no?

[Paul77nz 8]

It successfully played, no?

@@Luke

 

Not really. Full transcoding of the 4K original absolutely chokes the server (which has decent specs) causing the resulting video to stop and start constantly. In addition it drops the HDR when the video is transcoded.

 

But even if the transcoded video played more smoothly, it shouldn't have been transcoded in the first place when resumed. It should surely direct stream the video and transcode only the audio when resumed, the same as it does when playing the file from the beginning.

 

Thanks again.

[Luke 37132]

Ok, we'll do some testing and try to reproduce this. Thanks.