As an update, I managed to fix my issue. I was using MP4Box 0.8.0 due to the new version not being available for download, and I had compiled the wrong branch by mistake (like I said, I’m still a noob to all of this.) So I am happy to report that with the latest version of MP4Box, I am getting Dolby Vision with LPCM 7.1 audio to playback on my NVIDIA Shield 2019. I have multiple audio tracks embedded as well, including the Atmos MP4 (for if/when a player is ever released for the Shield that can handle Atmos and playback Dolby Vision) and the AC3 track for maximum compatibility. For some reason, the AC3 audio track causes the entire stream to transcode though, but I would chalk this up to user error (I’m betting I’m ripping the audio incorrectly in FFMpeg) Either way, all that’s left for the purest rip possible is to get Atmos to playback in MP4 when paired with a Dolby Vision audio track, which is already proven to be possible since a HTPC can playback Atmos in MP4 without an issue. Fingers crossed this happens sooner rather than later.
The process is the same. FFMpeg is taking the audio stream you have, ripping it and encoding it into whatever format you want.