[Stront]

Just a variable with playerid array.

Код:

new Streaming[MAX_PLAYERS];

//When you use PlayAudioStreamForPlayer
Streaming[playerid/i/whatever you use in the scripting] = 1;
//When you use StopAudioStreamForPlayer
Streamer[playerid] = 0;
//When you want to detect if it's streaming something.
if(Streamer[playerid] == 1)

It seems basic for me, but I dunno if it's gonna work. You'll have to do that in all the PlayAudio and StopAudio used.