So I did more research and here it is (this was originally posted on the J2O discord so please forgive weird line breaks)

It's likely that Jazz's exes are borked for one reason or another since the difference between the config of my regular DB and gog's DB are just details such as different mounted dirs and so on, nothing major that should affect anything.
Or that GOG's dosbox is broken, but I've tried changing it to ECE and it resulted in stuttering sound and constant framerate issues no matter what settings I've put in, so...
Also, I'm not sure if resolution change is to blame either - I've noticed that the stutter happens few frames AFTER the resolution is changed.
And even if it is caused by the res change, it has no business being that long. 200ms-half a second, maybe. But few whole seconds?


//edit: Another tidbit: I've ran JJ on DosBox 0.74 in the past (which was a pirated bersion because it wasn't available for purchase back then outside of very expensive eBay listings) and haven't had any issues of this kind.

From what you're saying, darkhog, it seems there is something not quite right about this GOG version. The game has been a proper, royal, pain in the bum to run in any sort of satisfactory manner. Myself, I thought I'd got there in the end (with a lot of help from kind GOGers), but here's the thing ...

So eventually it was working flawlessly, but then I fired it up again the other day and the stuttering had returned worse than ever - for no apparent reason! I reinstalled the whole thing, did the tweaks ... bingo! Worked again. Guess what? Loaded it up a day later ... the stuttering has returned. I can't understand this. Once it was working properly I was terrified to mess with any settings, so naturally I did not tweak a thing; it just happened all by itself. I've never known problems like this with previous DOSBox games I've played.

Another thing of note: I picked up Epic Pinball and have experienced the exact same micro-stutters / lags / frame-skipping as with Jazz.

There does not seem to be any magical, suits-everyone-solution for Jazz either. One tweak or CONIG setup will work for one person, but not for another, and very few solutions completely rid the game of all problems for anyone from what I've observed.

*Edit to note: The stuttering I referenced is in-game, not the loading screen / level start type pauses. I had that problem too, but that was resolved with SVN ECE. *Edit to correct: Meant SVN Daum*. Apologies for the length of this post too.

Yup. Case in point: ECE doesn't work for me, it makes things even worse: Even on settings that worked right (except of the stutter on level load), which was Overlay output, scaler none, it got terrible stutter (in the ECE) that made the fps crazily inconsistent and sound all sort of weird and corrupted.

Agh sorry, I meant *SVN Daum* resolved things for me. I got confused with ECE - which I'm using with Epic Pinball, as Daum messes that game up for me. Got DOSBox's coming out of my ears lately; I'm practically dreaming of DOSBox when I go to bed at night!

I actually have the same situation as you here; with Jazz, ECE made things much worse, but Daum is working like a charm as long as it's in Direct 3D. As long as I use that output, it works well all the time - although I had to manually set the cycles to 10000 as there were moments of slight audio stutter and lag.

I gave up trying to use Output: Surface, Resolution: Original. It's like it would work one time, but then the settings effectively would not stick or get messed up.

Got any link to the daum version? Googled it, but all I got was bunch of German sites and I don't speak German (yet).

http://ykhwong.x-y.net/

It works!

Well, not quite, there is still some slowdowns but they can be ironed out in config and are rather of "slowmotion" kind, not any serious slideshowing or freezes. Mainly happens in menus and such.

Try this: https://www.gog.com/forum/jazz_jackrabbit/jazz_jackrabbit_vsync/post5
You might want to make your own tweaks to the cycles and things like that, but those should at least be some good, working, base settings to be going on with.

AFAIK JJ works with cycles set to max so whatevs.

OK, I'm so done messing with Daum, SVN builds, whatevs. Found different way that works just fine (no freeze, no slowdowns). Funny thing is, I would never bothered with it if I didn't want to make a DOS game of my own, in QuickBASIC of all things, lol.

So this is what you're going to do:

1. Stop launching JJCD via the shortcut, if you experience any issues such as that freeze or slowdowns.
2. Download this build: https://www.dropbox.com/s/nj7sgzkcefy4rot/DOSBoxVS2015Binaries.7z?dl=1 and unpack its contents into your favorite directory (windows, for other platforms you're going to download sources and compile it from them).
3. You will run dosbox-lfn.exe at least once after that and then close it
4. Use this config: https://pastebin.com/raw/VQyZqW6F
5. Change the last line as needed to the directory where you installed JJ (I have a bunch of other DOS games that I had similar issues with so I've left it where GOG installs games by default), the config is found on windows under %appdata%\local\dosbox\dosbox-SVN.conf
6. When you feel like playing JJ, you'll launch dosbox-lfn.exe (make shortcut for convenience), navigate to the folder where you installed JJ and type JAZZ, then press enter. If you want to play Holiday Hare 95, you shall navigate to the directory called HH95 that is under JJ's directory and you will type JAZZ, then press enter.
7. Speed problems will be gone and you will be a happy bunny rabbit

Seriously though, I have no idea what is so f'd up with the default DOSBox config/binaries used by GOG. Perhaps it could be better integrated so you could launch it with the GOG shortcuts, but I can't be bothered to do that.

Your suggestion worked for me and I don't see any verticaltearing, I don't actually know what vertical tearing looks like. i've noticed these short pauses on all of my DOS games from GOG, but they generally only happen when starting or quiting a game, these brief pauses were most noticable in Jazz Jackrabbit. i'm running my games on a new HP laptop i just bought last week and i thought initially these pauses were caused by the computer changing resolution or game mode setting or CPU speed or something like that.