I've found this really hard to track down via search engines since most discussion is on encoding 5.1/4.0 to 2.0. This thread from that discusses how it can be done using graphedit but it's pretty dated, some of the filters used don't seem to be used anymore, and I haven't had any luck with it:
Demux a Dolby Surround 2.0 file into separate streams? - VideoHelp Forum

I know this is possible as there's at least one release group online that de-matrixes LD 2.0 mixes to 4.0. Anyone done this before or know where to start?

I forgot I had this thread saved from long ago when I was first looking into this and it has lots of good info (from some members on here too) but would still love any input from anyone that has done this before.

A good read, thanks Yarp.

I think some people convert using foobar plugins. You might want to look at the pool of plugins on the foobar site. I think you can also convert using Dolby Pro Logic II via fmmpeg.

You could use hardware like a SDU4. I tried experimenting with this once but the unit I got off eBay didn't work and there's not a whole lot of documentation out there on fixing it.
But that would definitely be the most "accurate" way of doing it.

I've recently picked up a JPN LD of The Right Stuff and it sounds phenomenal. Better than any other track I've heard and has a lot less noise reduction, especially compared to the muddy sounding blu-ray. Unfortunately, the LD track is pretty lacking in bass without much information below 50hz. My goal here was to attempt to expand the 2.0 track to 4.0, duplicate the rears, and mix in the LFE track from the blu-ray. Wasnt sure if it'd work, but I synced the 2.0 track and I tested this out last night and mixing in the LFE track seems to work.

(2023-08-17, 03:12 PM)PDB Wrote: A good read, thanks Yarp.

I think some people convert using foobar plugins. You might want to look at the pool of plugins on the foobar site. I think you can also convert using Dolby Pro Logic II via fmmpeg.

I tried both the ProLogic foobar plugin as well as the FreeSurround one last night. I liked the freesurround one better but there was still a lot of crosstalk between channels. But I ran it through my theater last night and compared the foodbar'd versions to what my Denon 4500h's Dolby Surround is capable of. I've seen some talk about how the DSU probably doesn't function like the old ProLogic I or II but I was very impressed at the lack of crosstalk, especially during speech. The DSU seems very good at pulling the out of phase info out of the track with little crosstalk.

Another option I was thinking about, especially if the DSU ends up being the best option, is to simply play it through my 4500h and setup my pre-outs to send somewhere to record.

(2023-08-17, 03:25 PM)stwd4nder2 Wrote: You could use hardware like a SDU4. I tried experimenting with this once but the unit I got off eBay didn't work and there's not a whole lot of documentation out there on fixing it.
But that would definitely be the most "accurate" way of doing it.

I was looking at SDU4s last night and wondering if they would be that much of a difference over the software options but I'm not sure. I have a LD audio track of Home Alone that I think was run through an SDU4 but it also has plenty of crosstalk between channels.

Not sure if you've read spoRv's blog posts from a couple years ago:
- https://blog.sporv.com/surround-test-1/
- https://blog.sporv.com/i-was-shot-today-...parison-2/

In my opinion, after having tested software for a long time to separate Dolby Surround tracks into 4.0 or 5.1 (Surcode Pro Logic, foobar with freesurround, and other less known software), I finally tell myself that all these solutions will never give as good a result as the original 4.0 mix, and at best, will perhaps equalize with the Home Theater decoder.
And a person wishing to listen to 5.1, already has a Home Cinema, and has equipment capable of decoding Dolby Surround.
Rather than burdening the files with a pre-decoded 5.1 track I would leave the 2.0 as it is, even though people have different decoders they all seem to be doing a decent job of decoding.
I understand that one may want to obtain the decoding originally planned, but apart from capturing the audio output from an old Dolby decoder, the other solutions will only be one more alternative among dozens of others.