Granted maybe realplayer was a wrong example, but I know film conservationists who can tell you that there is a huge gap in their archive that stems from obscure digital formats that nobody has the funds for to reverse engineer.

It is great if todays VLC plays your file. Just make sure to regularily check over the course of the next 50 years if that is still the case. If stable archival is your goal there not many things that beat lasering something onto physical film where in the worst of situations you'd be even able to look at the pictures with your own eyes and rebuilding a projector after the collapse of society is probably easier than rebuilding a computer running an OS that reads that disk with software that plays that file of which you might know precisely nothing without being able to decode it.

This is why e.g. national archives use film for storage.

Not that this is a feasible solution for the private person, but sometimes considering a low tech solution might be the least complicated "do and forget" option.

If your ancestors find your bluray disks or some old hard drives they might find some challenges:

- they might not know what those are

- if they have an idea what those are, they might not have the connectors or devices needed to play them back

- if they have the devices needed the device might not be able to read the file system because it is not supported anymore

- if the filesystem is supported, the file format might not be

This is a lot of hoops to jump through for something where you don't even know what is on it.

Meanwhile a old picture book can be just looked at.

This is maybe a weird corner case, but I had no luck with the RealMedia files here: https://chance.dartmouth.edu/ChanceLecture/AudioVideo.html on a Mac, particularly the Susan Holmes lecture on "Probability by Surprise". It's some format that has video + synced web pages.

I eventually downloaded the zip and made it into an iso that I could mount in a VM of Windows that had RealPlayer installed. Failed attempts included VLC and some other Mac video player (Elgato?), and trying to navigate to the page from a Windows VM (no https). I would love to here of a less tedious solution.

VLC can play the video! Open HOLME.RM and choose the second video and second audio track using the menu.

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ffplay plays it just fine by default, but neither VLC nor mpv does, that's rare! Funny I found this thread while searching for a particular discussion about ffplay.

Looking at its output, libav thinks the file has 15 streams: 5 data, 3 audio, and 7 video. Of these only the mentioned two are playable. Evidently ffplay uses ffmpeg's probing and stream selection, while the other players just try to play the first of each type.

Of the other streams, ffmpeg `-c copy -f data` can only dump two of the data streams. These contain the names of the HTM files and what looks like more compressed data. Searching turns up nothing but other university websites describing how to use it - this synchronized slideshow format (apparently not SMIL) looks lost indeed.

note to self: mpv can be started with `--aid=2 --vid=2` (1-indexed), but VLC has only `--audio-track=1` (0-indexed) and lacks a video track option despite having an open issue since 2009. For completeness, ffplay would use `-ast 6 -vst 9` (undifferentiated and 0-indexed).

Thanks for figuring this out! The slideshows have visible timestamps so it's not too hard to keep up manually.