So, here's what I'm trying to do right now, and probably nobody knows the answer but here goes. What I'm trying to set up is an entity that emits a constant sound, but is also toggleable. So when you turn it off, the sound goes silent, and when you turn it on, the sound starts up again.

Problem 1: if you are out of hearing range when it turns on, the object will be silent when you get close.

Problem 2: if you save and reload the savegame, the object will be silent.

The basic cause is that sound() calls are fire-and-forget and quake assumes the sounds are short-lived so the above situations won't be much of a problem.

I've tried various solutions, the latest is various versions of "restart the sound every 1 second or so." The problems with that are first, when you approach the object its sound starts up suddenly instead of fading in, and second, you can hear obvious repetition when standing next to the object.

Increasing the frequency of sound() calls reduces the sudden start, but worsens the repetition. I'm going to try and improve this hack by having 3 or four different sounds, and playing them at random, so that you don't hear any obvious repetition of sounds. 

it is possible, but it's slightly hacky.

unfortunaly, i don't remember who told me about this method... it may have been lordhavoc, but i'm not sure.

anyway, the engine can only load ambient sounds (true ambient sounds that the engine keeps track of regardless of player position) properly when the map is loading up.

you can trick it by using an unused SVC (29). unfortunatly, you can't specify a filename for this, you need to actually feed in the # of the sound in the order as it was loaded into cache. �_�

the best way to do this is to precache your ambient sounds first, this way you don't have to worry about anything being precached before it and mucking up your ambient sounds.

the first sound precaches are located in weapons.qc (W_Precache). load any new ambient sounds in there at the top of the function.


float SVC_SPAWNSTATICSOUND = 29;

Define the constant for convenience, and write a little function to use it:
void(float soundnum, vector org, float ambvolume, float atten) spawnambient =
{
WriteByte(MSG_ALL, SVC_SPAWNSTATICSOUND);
WriteCoord(MSG_ALL, org_x);
WriteCoord(MSG_ALL, org_y);
WriteCoord(MSG_ALL, org_z);
WriteByte(MSG_ALL, soundnum);
WriteByte(MSG_ALL, ambvolume * 255); //translate this into a value between 0 and 255...
WriteByte(MSG_ALL, atten * 64);
};

now just call your new function with whatever sound # you want.

this will spawn a true ambient sound into the map after it was loaded, and won't stop playing when you move out of range.

you'll notice the lack of any channel specification... i'm not sure if it's possible to turn it off again after it's been turned on. i can't check right now, but i'd guess using a non-looping sound will give you that 'non-looping sound for ambient sound' error, since it's not just a normal sound call.
but you will at least be able to turn it on. :x

maybe someone else can build on this? 

Interesting, it would only work if the it could be turned off again somehow. Hmm.... 

my hack with the multiple random 0.1 sec sound effects works fairly well, but the problem is you can hear a sort of distortion/clip sound when the new sound overrides the old (the same sound you hear when a sound isn't looped correctly, meaning the waveforms don't line up and there's a sort of audio seam.) I may have to live with it. The sound effect for this has a lot of white noise in it (it's a steam jet) but I also wanted to do this for forcefields, and i'm worried that sound won't hide the clipping artifact as well. 

As it happens I was writing some code yesterday that might help you out. What it does is provides you with a function that is run once when you load a saved game, but not when the game starts first time round. Replace the StartFrame code in world.qc with the following:

nosave float loadflag;

void() LoadGame =
//runs if player has just loaded a game
{
dprint("*****new game loaded******\n");
}

void() StartFrame =
{
teamplay = cvar("teamplay");
skill = cvar("skill");
framecount = framecount + 1;


if ( framecount == 3)
loadflag = 1;//started a new game, not loaded a savegame

else if(!loadflag && framecount > 3)
{
LoadGame();
loadflag = 1;
}

};

You'll need a compiler which supports the nosave keyword for variables, frikqcc and fteqcc are the two I've tried. The idea is that the loadflag isn't saved in the savegame, and so gets reset to 0 when you load a game. The reason you have to wait until the third frame before you set it originally is because when quake loads a savegame, it runs the whole worldspawn procedure to rebuild the precache lists. The worldspawn procedure includes running two game frames, to give things a chance to droptofloor etc. So if you change a nosave variable during those frames, it'll have that value when you load savegames - which might be different to what value it had when you saved - but it's not what we want here.

So that gives you a way to restart the sound after someone loads a game, replace the dprint line in LoadGame with a function that searches for all the sounds that should play and restarts them.


As for the other problem, one possible solution would be to calculate the distance at which the sound can just be heard, assuming you started in range of the sound. Then have the entities search for a player within this radius regularly and start playing when they just enter it. Might be more difficult to make it work in coop.

If you do that, then you don't really want to use findradius for the job, it's a bit excessive to have 10 findradius calls every second per entity if you have a few of these things about. Better to loop through the first maxplayers worth of entities with the nextent command, since the players are always the first entities on the server. Then just test the distance for each of those that turns out to be a player. Whether
vlen(vec) < d
is faster than
vec_x*vec_x + vec_y*vec_y + vec_z*vec_z < d*d
is something I've been meaning to test. One is trying to calculate the square root of a quantity, but it is a builtin, so it's faster than qc code. Probably not necessary to get that kind of saving here if you're testing at most 16 entities, and most of the time just 1, it's just an interesting question. 

yeah, this findradius idea is the direction i'm thinking of going next. One challenge is, the code to play a sound will not bother playing a sound if both right and left stereo channels can't hear it, and the calculation to determine the volume at each "ear" (channel) is somewhat complicated. Not sure if i'll need to recreate that in quakec or if it will suffice to estimate the radius in some other way.