Videos detailing exactly how to do specific things and not general things would be the most helpful.
You are not the first person to want videos and I doubt you will be the last. However I truly struggle to conceive of a format that would do well here and I have not seen one, and there have been a few efforts, that get close.
To that end what kind of format would work here? I will run through my present thoughts on the subject
On specific things then the trouble often becomes that you now know how to do a specific thing -- I tell you how to relink the sound and sequenced banks in Tetris DS and you know how to relink the sound and sequenced banks in Tetris DS. I could go a tiny bit more abstract and talk about the SDAT format as a whole but then I have to cover addressing, endianness, general concepts in file formats and more besides. Doing that loses those that know* and not doing that loses enough of those that do not. I do not care much if it is just archival for my purposes, my personal amusement or something but if I have set out to teach people things then I have problems. Granted people will watch hours of let's play videos so I might be underestimating the boredom threshold but I doubt it. There have been times when seeing a mouse cursor move does better than someone speaking or trying with still images, some of the Final Cut or Adobe After Effects/Premiere stuff on http://www.youtube.com/user/Filmriot
being a great example for me, however they purposely hold back and have to say "this is what worked for this clip, figure out what you need yourself" a lot. Sometimes it is even an instant clarification/realisation... but not often.
*I pick up a book on a new programming language and it wants to teach me about the exciting world of boolean logic and the sort of operations that go along with it, mainly as they are very useful in programming, and struggle to not skip ahead (which I can't do as I will not then know the syntax and quirks). I make it through that and chapter two is on the basic types of programming loops and I lose the will to live. I pick books deliberately to avoid this but sometimes it happens anyway.
Reversing a format. I can sit at my computer for hours looking at things, doing searches for crumbs of data, trialling and ultimately failing 400 times, whizzing around in a hex editor or something as my whims take me (that bit which I think is either a pointer or a size value said that, this would be where it is if it is that, it is not but I see something else so is it offset or something, how about I slice that out and see, what else is known that I might use that instead, nothing so I guess it is time to compare 30 of these files and rapidly switch between them to see patterns in hex... being something that could have been snatched directly out of my head). I vocalise (or subtitle) what I am doing and thinking and it takes twice as long which is still doable. The result however is some of the least compelling footage you would ever see. I might be able to make something somewhat compelling for another ROM hacker (it would turn out something like https://www.youtube.com/watch?v=Qjw0NDeP-0Q
) but no chance of it being a useful tutorial.
Some of my favourite videos to watch are those from machinists and woodworkers. A lot of it is "cut this, drill this" but you move even into the basics of accuracy or strength (and there are serious bonuses for doing that and more for doing more) and, well there is a reason it is considered a skilled trade. Those would be what I look to but I realised the time is kind of reversed -- you know what you do and just have to set it up, run through some logic and then spend hours drilling and reaming 60 holes, surface grinding something, milling something or playing on a lathe, back in ROM hacking I figure out the pointer and name scheme for an archive format and a few minutes later I have a batch file that has just sliced it up and handled any decompression, or maybe a few hours and I have a python script to handle building as well. Even something more labour/tedium intensive like mapping out an encoding and making a table is probably not going to be much better; you watch me brute force one bit of punctuation and you have watched the lot, same idea if I have a custom kanji table/order to deal with.
Oh and I have various numbers of screens, usually at least two with one in portrait mode and I think I have a compelling use case for 4K screens as I could really do with the screen real estate for hacking. That does not make for nice to edit video.
There are things that make so much more sense, though most are incidental rather than any kind of tutorial. I think my favourite was OAM (the thing that handles the location of sprites on a screen) for the GBA and DS. I was writing a document and covering it and where I can kind of show it in words and text then 2 seconds of watching an emulator and the OAM memory update in real time makes it completely obvious -- if it was rendered in neon green text then it would have looked like a scene from the matrix as it perfectly mapped/mirrored the things on screen, or in this case the two screens of the DS.
There is a part of me that wants to tell me that I am over thinking it and should just do it. On the other hand we know machining/woodworking makes for compelling TV (how many years did New Yankee Workshop run?) but I have never seen a coding TV show worth a damn that was not a science show or lecture or something that happened to be about algorithms and such like. I linked it before but https://www.youtube.com/watch?v=uFfq2zblGXw
seems fitting again, I have also seen several hosts of Discovery channel various TV shows say parts were cut because they were just coding*. I watch any of the command line/wireshark/coding videos on something like https://www.youtube.com/user/Hak5Darren/videos
and even if it is something I want to know and even with the rapid editing and energetic hosts I find myself distracted and falling asleep in my chair (and as previously covered I can do it for hours on end myself).
*two of the big ones were Mythbusters have said they wanted to do a lot more computer related things but were shut down or shut it down themselves, another was in various defcon or similar American hacker conferences a handful of the people presenting that Prototype This show made similar comments (by the way if you were a bit ambivalent about some of those presenting that show then watch those conference videos, or don't if you don't want to dislike Discovery Channel editors/editing policy even more than you probably already do).
It was once said that the best person to teach something is one that just went through it. You risk a few bad habits or heuristics that fail in the real world/more fiddly stuff but there is more than an element of truth to that. Might that also be a problem here?