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Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 3:29 pm
by tucobenedito1
Hello,

I can't find a way to convert a True+Atmos audio stream to EAC3+Atmos in Handbrake. I want to do this because I am creating M4V files and EAC3+Atmos is supported in the m4v container but TrueHD+Atmos is not. It appears Handbrake does not have a downmix to EAC3 today. Is that true? If so, is that a potential future enhancement in one of the dependent libraries like ffmpeg?

Assuming I can't do this right now, is it reasonable to encode my m4v files today and later add a downmixed EAC3+Atmos audio stream to the m4V container? I'd like to avoid complete re-encoding if possible.

Thank you

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 3:54 pm
by Rodeo
You cannot "downmix" TrueHD to E-AC-3, it's a re-encode. Also, none of the open source decoders and encoders support Atmos right now, if I recall correctly.

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 5:57 pm
by tucobenedito1
Thank you @Rodeo. Sorry about the terminology issue. Atmos aside, is it possible to re-encode a lossless format like TrueHD as E-AC-3 so I can include it in the M4V container? I think ffmpeg supports it, but do not see an option for E-AC-3 in Handbrake other than passthru of the E-AC-3 audio stream.

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 6:42 pm
by Rodeo
Are you sure you have the latest version of HandBrake (1.2.2)? It should be able to mux E-AC-3 in MP4 thanks to FFmpeg, though perhaps we didn't remember to enable it…

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 7:25 pm
by tucobenedito1
@Rodeo I do not see it in Handbrake 1.2.2. My MKV file has a TrueHD (7.1) audio channel but the only available codecs are aac, mp3, and ac3. All others are pass-through.

To verify my understanding and what I am trying to do, I want to add an e-ac-3 audio channel when creating a m4v file in handbrake in addition to aac and pass-thru ac3 that I do today. I have presumed this would be possible since ATV 4K supports e-ac-3, but I have been unable to find any place verifying e-ac-3 can be in the MP4 container.

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 7:33 pm
by Rodeo
Hmm, then I guess we need to add it. The FFmpeg libavformat muxer is E-AC-3 in MP4 capable, IIRC.

In the meantime, you can't do what you want with HandBrake, I guess.

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Tue Mar 05, 2019 8:08 pm
by tucobenedito1
Thanks @Rodeo Will you need a Handbrake activity log from me to ensure the issue gets submitted and addressed, or is my description above sufficient. I will be glad to test this when an update has been made :-)

Also, it is my understanding I can't add an external audio track to a MP4 container from within Handbrake today. I am presuming I would need to use ffmpeg directly to mux the e-ac-3 audio channel from my MKV and add it to the MP4 container I'd previously created in handbrake. Is this correct?

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Wed Mar 06, 2019 12:16 am
by JohnAStebbins
It works in the Linux version. So libhb supports it. What GUI? Perhaps it got missed somehow on one of the GUIs

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Wed Mar 06, 2019 1:07 am
by tucobenedito1
I am using the Windows version 1.2.2. Will try to locate a Linux system to verify issue is Windows-specific. However, in short-term may try to use ffmpeg directly to add the eac3 audio stream to the source MKV file so I can do a pass-thru to my output MP4 when encoding via Handbrake. Would love to get this fixed and glad to test it in order to avoid the extra step on my end to manually create the eac3 stream. Would also appreciate any other guidance on alternative ways accomplish the same.

Thank you

Re: Downmix TrueHD+Atmos to EAC3 Atmos?

Posted: Wed Mar 06, 2019 9:11 pm
by tucobenedito1
FYI: Verified this is an issue with the Windows UI but not Linux with the same MKV file