I would like to play UFO Defense with the original GOG's dosbox version... But I'm experiencing like the title says crackling sounds and some lags. Is there something I can do ?
All help is welcome :)

Have you tried that 64-bit version of dosbox? It's all I use anymore. here

Alternatively, give OpenXcom a spin.

DOSBox performance varies across different machine setups, so some tweaking to the DOSBox settings may be required to get it running optimally for your machine.

As you mentioned crackling sounds, here is a GOGWiki entry for Crusader: No Regret where some people had the same kind of issue.

[url=http://gogwiki.com/wiki/Crusader:_No_Regret#Skipping.2Fpopping_audio]http://gogwiki.com/wiki/Crusader:_No_Regret#Skipping.2Fpopping_audio[/url]

The article mentions tweaking the DOSBox config file for the game so try those settings and see if that helps.

Similarly, GOG tend to use DOSBox 0.74 (I've only seen them use SVN builds when 3DFX was needed). So you could try replacing the DOSBox version provided by the GOG installer with an SVN build (DOSBox Daum - http://ykhwong.x-y.net/).

For OpenXcom, I would have liked to try the "true original" at least some hours before :P But I'll try it at one moment, sooner or later that's certain ;) It helps, it seems that crackling sound is gone ! (prebuffer value wasn't the same as in this solution : it was at 80, in the solution it is at 50)
But it didn't happened all the time, so for no, nothing certain. I didn't even knew there was a 64bit version XD
Okay... It seems that I can't download what's on the download page. But there was a link (at the bottom of the page " For clean SVN builds, click here - emucr.com") which finally lead me here : http://www.emucr.com/2016/03/dosbox-svn-r3972.html : is this the right version ?
Okay, stupid question... What do I do now if it's the good file, I simply decompress the whole archive in the DOSBOX folder in the game folder to replace older files of dosbox ?

Thank you very much for your help you two ;)

Edit : What does the 64bits version change ? (except that it is more up to date, and so certainly more bug-free and more optimized I suppose)

The link you've found for the clean SVN builds is fine, but if you want to try SVN Daum then use this link instead (taken from the download page): [url=http://www.msu.edu/~yootaewo/_db/20150125.7z]http://www.msu.edu/~yootaewo/_db/20150125.7z[/url]
You might have to right-click and save as if you find your browser is trying to display the file as text. You'll need an archiver that can read 7-Zip archives, though, like 7-Zip or WinRAR, in order to open the 7z file.

Once you have your chosen DOSBox SVN version, you should just be able to extract it over the top of the DOSBox folder in the GOG installation, though what I would do is rename that folder to keep it as a backup, then create a new DOSBox folder to put the SVN DOSBox into. You will then need to copy over the .conf files for the game. Note that if you want to use new features from the SVN DOSBox, then run that DOSBox with no conf file in order to create a default one, and copy any particular settings you are interested in over into the conf file for the game. I'm aware that this might start getting a little confusing (and I don't know what level of experience you have with these matters), so if you find the existing edit to the sound settings works, I'd go with that, and would only look at DOSBox SVN builds if I felt I really wanted to have a play around and see how well I can get the game running. 64-bit just means it is a 64-bit executable, so a 64-bit Operating System (a 32-bit OS will not run it) should in theory run it better as it can utilise a greater amount of RAM. I've not tried a 64-bit DOSBox myself to see what difference it makes. DOSBox Daum comes with both a standard 32-bit executable and a 64-bit executable.

Don't rely on more up to date being more bug-free. Later builds add new functionality and that can create more bugs!

I found a FAQ explaining differences, GOG dosbox is a clean version ?
If you think that SVN Daum is more interesting to use, I'll try it ! I must have something wrong with my browser (or firewall) this downloading link didn't work too : it leads to a page "The connection was reset".
I can download an older build (20150103.7z), but not this most recent one. I tried disabling antivirus and changing webbrowser, it's the same problem.
No problem with the 7z part, I know this ;)
Concerning my skills (it's always hard to know what someone you try to help know or not XD) : I have a little more than the bases (thanks mainly to experience), and I can try to do some things by myself, but I don't know enough to really find "complex" solutions (except sometimes with a lot of patience and luck combined).
I already looked a little in the dosbox.conf options in several games for example, but... it takes me a lot of time, and without some indications, I can't do a lot by myself (that's why I asked here, I know several games have small troubles in dosbox, but they have often specific solutions too :P). This is this kind of points where there are a little bit too much shadows for me :P (in short, I don't really know what I should keep)
I'll try already this, and when I'll be able to download SVN Daum, I'll try it too to see if there are differences. You're totally right, I talked too fast ;)

Thanks a lot for your help and patience :)

as an extreme fix for the sound you can try turning sound off completely for X-com in the sound mixer or equivelent in non-windows os

GOG usually provide the normal, 0.74 release of DOSBox, not an SVN build (the official releases haven't been updated for a very long time). I've only seen them use an SVN build when the DOS game uses 3DFX so that they can make it use it via a 3DFX wrapper (usually nglide) and turning on the 3DFX options in DOSBox.

I do pretty much the same as GOG, in that I use official 0.74 unless I need something from SVN. Mainly because I'm a little lazy to keep messing about with new settings all the time unless I need to. I have used SVN Daum and I have used Gullikoza's (don't think this one is updated any more though).

And no worries, happy to help out. :)

You can use it with any DOSbox game...it's "the gamer's DOSbox" with lots of stuff besides the 64-bit version of DOSbox that have been added specifically for games...a nice selection of shaders which can often make a very pixellated low-res DOSbox game look much better, etc.

Like was said earlier in this thread, the 64-bit version accesses more ram and other resources than the standard DOSbox can access. I also use it to scale up very low-res games to display at 1920x1200 or higher--there is so much you can do with it via the configuration files. What GOG supplies is fairly bare-bones and it does the job, but often SVN Daum can simply do the DOS emulation better for most games. I also use one single configuration file and that is what GOG used to do as well; but now they've decided to use 2-3 separate configuration files--one to do the sound and/or graphics setup, one to configure the options, and often still one more config file to actually run the game itself...;) When I buy a DOSbox game from GOG the first thing I do is install SVN Daum DOSbox in its place. It takes a slight bit of effort but I think the results are definitely worth it...!

You should definitely give it a whirl and see how you like it...;)

If you are looking for a vanilla SVN build you want this VOGONS thread.

When people mention lag, is it when you are on multiple levels? I noticed in both X-com and TFTD, the higher the level that my troops were on, the slower the game performed. At levels 3 and 4 it was like slow motion for everything which made Battleship missions a real pain...but when I jumped down to ground level, the game was fine.

EDIT
: well I've tried different sound settings to no avail. I have no intention of installing some third party fix or delving into esoteric builds in order toget this running. I feel it ought to run out of the box and not require this so I'll be uninstalling. Quite a disappointment.

Well obviously this is very old, but we're still buying X-Com Apocalypse in sales. I too suffered from lag and crackles etc and after searching on the net i found these settings which have 99% sorted it out.
nosound=false
rate=48000
blocksize=4096
prebuffer=20
[url=https://www.dosbox.com/wiki/GAMES:X-COM:_Apocalypse]https://www.dosbox.com/wiki/GAMES:X-COM:_Apocalypse[/url]

Please, try installing the latest game version (now with cloud saves).

I also had that sound issue and this update fixed it for me.