I said to always choose the hd audio track and convert it to eac3.

I said otherwise it's just hd audio / ac3. I said if you're lucky there's an eac3 7.1 track sometimes on the movie. I said to never demux the ac3 track, cuz it's crap. Then you say to demux the HD audio and convert it to e-ac3, but before that you admit that without a licensed dolby encoder, you can only get non-Atmos 5.1.so what's the point of converting when you can just demux the ac3 track? The one that's created by the movie makers is likely to be as good as or better than one that you create from converting from one format to another. You say don't demux the ac3 track, but then you admit that most movies don't have a DD+ track to demux directly. You seem to be talking out of both sides. lossy dts-hd or true-hd dd+ e-ac3 sounds waay better than regular lossy dts or dd ac3. then use eac3to or ffmpeg to convert it to e-ac3, and create your mp4 with that. usually movies only have hd-audio or dts/ac3 tracks though, so always pick the hd-audio track to demux. unfortunately only 5.1 (no atmos) is possible unless you have a licensed copy of dolby media encoder suite. if you're lucky, some movies come with an eac3 dd+ 7.1 atmos track, but if not you have to do some converting. it's still lossy, but at a much higher bitrate than regular ac3 (1536kbps vs 192kbps) and you get atmos (just like Netflix, etc).

the best that mp4muxer supports is actually e-ac3 dolby digital plus 7.1 + atmos.

Hevc xmedia recode