JEDIT: ignore the post that was here, I was thinking of mkvtoolnix.
Okay, so tsmuxer should be used to demux the video into its independent streams. By definition, it doesn’t reencode anything - however, since you’ll be using this to convert DTS-HD to DTS, technically you’re going from a lossless encode to a lossy one, but that shouldn’t be noticeable in any appreciable way for the mono track. I think the only audio track included where this might theoretically have a noticeable effect would be the 5.1, and even then I’d be a little surprised if you said you could actually tell the difference.
So. If the DTS-HD MA mono mix has a standard DTS core (DTS-HD MA always should, but 1.0 is a weird format for DTS-HD MA, so it might not), here are the steps you should take:
- Open the MKV in tsmuxer
- Uncheck every track except the one you want (the mono mix)
- Select the track
- Check the box that says “Downconvert DTS-HD to DTS”
- Under “output,” click the “demux” option.
- Choose your output folder
- Click “Start demuxing”
You can also use it to split off the MKV video into an independent video file, but that’ll require you to have at least 3x the HDD space of the original MKV by the end of this if you don’t delete the original MKV after this step, which I don’t recommend. Just demux the audio you want, you can steal the video from the original MKV in the next step and you’ll only need a little over 2x the HDD space of the original file.
Anyway, when it’s done demuxing, you should end up with a .dts file. Next, you’ll need mkvtoolnix.
- Open the original MKV file (“Add Source Files”)
- Open the .dts file that was output from tsmuxer (“Add Source Files”)
- Uncheck all the other audio options you don’t want - ensure that, at minimum, the video file (h265 or h264 for the 1080p version) and your DTS audio file are checked (you can keep any subtitle files or chapter markers, too). You might also want to set the language of your audio track to “English” - if you have multiple audio tracks included you might also want to set your preferred one as “default,” but it’ll be automatic if you only have the one audio track
- Set your output file destination (it’ll be an .mkv)
- Click “start multiplexing.”
When it’s all done, you should have a new MKV file with a standard DTS audio track that’ll play in your TV.
NOTE: If the mono track doesn’t have a DTS core (I don’t have it in my laptop’s HDD to check), this won’t work, but the 5.1 and 2.0 DTS tracks will almost certainly include a DTS core you can extract, so you’ll be able to pick the original 1977 stereo or hairy_hen’s 1977 six-track reconstruction to use if you can’t use the mono mix.