ffmpeg changes imaging of copied 5.1 eac3 stream

[amirms76]

Hey everyone!
I have encountered a problem when trying to remux the file below from mkv to mp4:
https://www.demolandia.net/downloads.php?id=27781967
I use this as the command: ffmpeg -i file.mkv -c copy file.mp4
I'm using ffmpeg version 4.1.1 win64 on Windows 10 version 1809

I play the file with Movies & TV app via headphones while Dolby Atmos for Headphones (with virtual 7.1 sound turned on) is enabled.
The problem is that the left and right surround channels are located differently when compared to the original file. The original ones are a bit wider and upper.
I even tried this but no success: ffmpeg -acodec eac3 -drc_scale 0 -channel_layout "5.1(side)" -i file.mkv -c copy -channel_layout "5.1(side)" file.mp4

What do you think the problem is?

[amirms76]

Well, I tried remuxing mkv to mkv and it seems that the problem is with mp4 container. What's more interesting is that if you do mkv --> mp4 --> mkv, the 2nd mkv sounds identical.

[pandy]

Check your decoder (different decoder used for different container) - or try to play with ffplay to confirm such behaviour.

[amirms76]

Check your decoder (different decoder used for different container) - or try to play with ffplay to confirm such behaviour.

I don't know how to check the decoder used by Movies & TV universal app.
Also tried ffplay, but it doesn't trigger Dolby Atmos for Headphones (it needs a surround source) and outputs stereo sound over my headphones.
Any suggestions?

[pandy]

convert both container to separate wav files, use audio editor to confirm your observations:

@ffmpeg -report -y -i %1 -vn -sn -dn -c:a pcm_f32le -f wav "%1.wav"

[amirms76]

convert both container to separate wav files, use audio editor to confirm your observations:

@ffmpeg -report -y -i %1 -vn -sn -dn -c:a pcm_f32le -f wav "%1.wav"

Checked with Audacity. They are identical.

[amirms76]

I finally could replicate the results of Movies & TV app using PowerDVD 18. You have to disable Audio under Video Enhancements in Settings. Set Output to 8 Speakers (or 6 depending on the file) with no effects and Dynamic Range to Boosted. This way a single file sounds identical in these two players.
Also PowerDVD doesn't have the problem that Movies has with mp4 containers.

[amirms76]

Another thing to mention is that PowerDVD 18 cannot decode Dolby Atmos. So if you have a file with Dolby Atmos sound, you have to play it through Movies & TV app to hear the effect of Atmos. The audio must be encoded in EAC3 not TrueHD, as Movies app cannot decode that. If you have a TrueHD Atmos track, the only way to play it correctly is to bitstream it.