Parcel Media Commands

Hello,

I am trying to build a narrated tour in SL. As the tourist progresses along the path, I want he/she/it to hear audio of me describing what they are seeing.

I have tried using llPlaySound to play sound snippets and that solution does not seem to work reliably, regardless of how I try to preload sounds.

It has been suggested that I should use llParcelMediaCommandList to play the sounds. I have played with this some but have some questions:

Does the PARCEL_MEDIA_COMMAND_TIME flag work with mp3s? I cannot seem to get this to start the audio at any place except the beginning.

Would it be better to use this function to play individual sound snippets as the tour progresses or should I make one long mp3 (say 5 minutes or so) and then try to play the appropriate bits using PARCEL_MEDIA_COMMAND_PAUSE and some combination of llSLeep or llSetTimerEvent?

Thanks,

Doug

I would suggest, that you have some sensor in an object that senses the Agents which are standing in front of your house/landmark (whatever is there to have the audio played to).

Then use the llParcelMediaCommand to play the specific mp3 for the detected agent only.

Use llSensorRepeat() to repeatedly scan for agents near the object.

Have a list of agents in the objects, which tracks to which agents the mp3 is currently played. If there's a new agent, which isn't in the list, start the mp3 for this agent. If there's an agent in the list, which isn't found in the sensor, stop the playing for this agent using PARCEL_MEDIA_COMMAND_STOP (he/she/it might still be nearby and still have the sound going on).

This way, if there's already an agent listening to the current soundbit and another agent shows up, the new one will hear the soundbit from the beginning, without having the first agent hearing the sound from the beginning, too.

With this approach, you can make an individual mp3 for every stop at your tour, which makes it easier to maintain them and makes the mp3 smaller.

The following is untested (and I'm sure one of our super-coders has a much more brilliant way to do it

list gCurrentAgents;

default{

	state_entry(){
		
		// Scan every 1 second for agents within range of 5 meters
 		
		llSensor("",NULL_KEY,AGENT,5,PI, 1);
	}
	
	sensor(integer num){

		integer i;
		list presentAgents = []; 	// Used to check whether we have an agent in the playing list who's not here anymore'
		
		// check whether all the detected Agents are already hearing the sound
		
 		for(i=0;i<num;i++){
			
			presentAgents = (presentAgents = []) + presentAgents + llDetectedKey(i);
	
			if(llListFindList(gCurrentAgents) == -1){
    			// This agent isn't in the list yet, so add it and start the sound
				gCurrentAgents = (gCurrentAgents = []) + gCurrentAgents + [llDetectedKey(i)];
 				llParcelMediaCommandList([PARCEL_MEDIA_COMMAND_AGENT, llDetectedKey(i), PARCEL_MEDIA_COMMAND_URL, "http://www.myserver.com/mySound.mp3", PARCEL_MEDIA_COMMAND_PLAY]);
			}
		}
		
		// now check if we have an agent in the list, who's not been detected
		
		integer l = llGetListLength(gCurrentAgents);
		
		for(i=0;i<l;i++){
			if(llListFindList(presentAgents, [llList2Key(gCurrentAgents, i)] == -1){
				// This agent is gone - stop the Stream for her/him/it
				
				llParcelMediaCommandList([PARCEL_MEDIA_COMMAND_AGENT, llDetectedKey(i), PARCEL_MEDIA_COMMAND_URL, "http://www.myserver.com/mySound.mp3", PARCEL_MEDIA_COMMAND_STOP]);
			}
		}
  	}
}

HTH

Thanks Haruki!

I haven't been able to get this script to compile yet but I'll work on it some more later.

Any advantage of using a sensor to trigger this as opposed to a collision event? I was thinking I would just trigger the sounds when the avatar ran into the (phantom) box. Would that be less laggy than a sensor?

Thanks again,

Doug

Hi Doug

Yes - a collision would work as well - but you won't have the chance to determine when the agent left the spot and thus, you couldn't stop the sound playing for her/him/it...

Hi Haruki,

That makes sense. Better than a collision event.

Unfortunately I cannot get your script to compile. I apologize - I am not a very skilled coder. I found some small errors (eg needing llSensorRepeat instead of llSensor), but I can't seem to debug the following part:

for(i=0;i<l;i++)
{
if(llListFindList(presentAgents, [llList2Key(gCurrentAgents, i)] == -1)
llParcelMediaCommandList(
[PARCEL_MEDIA_COMMAND_AGENT, llDetectedKey(i),
PARCEL_MEDIA_COMMAND_URL, "http://www.myserver.com/mySound.mp3", PARCEL_MEDIA_COMMAND_STOP]);
}


The llListFindList function gives me a type mismatch - perhaps the list "presentAgents" and the key of the current agent when the llListFindList function requires two lists?

I dunno. Sorry for being so obtuse.

Doug

Hi Doc,

You are missing a closing bracket, try this:

		for(i=0;i<l;i++)
		{
			if(llListFindList(presentAgents, [llList2Key(gCurrentAgents, i)]) == -1)
				llParcelMediaCommandList(
					[PARCEL_MEDIA_COMMAND_AGENT, llDetectedKey(i),
				PARCEL_MEDIA_COMMAND_URL, "http://www.myserver.com/mySound.mp3", PARCEL_MEDIA_COMMAND_STOP]);
		}

That should compile but I have not tested or read the rest of the code

Thanks Very...

Dr - didn't have time yet to try this inworld - hope Very's solution fixed it...

Hi Very and Haruki,

Thanks for all your help. I really appreciate it.

The script now compiles correctly, but I'm not sure it is actually doing what was intended.

The first part seems OK in that as far as I can tell, it will only play the mp3 once for each avatar. At least it only plays once for me. If I want to hear it again I need to reset the script.

So far so good.

However the second (problematic) part does not seem to work. Once the sensor detects me, the mp3 plays through to completion, regardless of whether or not I leave sensor range. This is not really a big deal since this will be part of a tour and the tour vehicle will follow the correct path at the correct pace. I'll put in a script reset so that my students can take the tour more than once and hear the audio again - some of them will need it .

I would be interested to figure out the second part though, just for my own scripting education.

Thanks again,

Doug

Hi Doug

Ok - I finally had the time to test this inworld... It was far from being perfect... sorry for that

Here it goes:

list gCurrentAgents;

default{

    state_entry(){
        
        // Scan every 2 seconds for agents within range of 5 meters
         
        llSensorRepeat("",NULL_KEY,AGENT,5.0,PI, 2.0);
    }
    
    sensor(integer num){

        integer i;
        list presentAgents = [];     // Used to check whether we have an agent in the playing list who's not here anymore'
        
        // check whether all the detected Agents are already hearing the sound
        
         for(i=0;i<num;i++){
            
            presentAgents = (presentAgents = []) + presentAgents + llDetectedKey(i);
    
            if(llListFindList(presentAgents, [llList2Key(gCurrentAgents, i)]) == -1){
                
                llOwnerSay("adding " + llKey2Name(llDetectedKey(i)) + " to the list");
                
                // This agent isn't in the list yet, so add it and start the sound
                gCurrentAgents = (gCurrentAgents = []) + gCurrentAgents + [llDetectedKey(i)];
                 llParcelMediaCommandList([PARCEL_MEDIA_COMMAND_TEXTURE, (key) llGetTexture(0),
                                            PARCEL_MEDIA_COMMAND_AGENT, llDetectedKey(i),
                                            PARCEL_MEDIA_COMMAND_URL, "http://212.112.241.88:8000/listen.pls",
                                            PARCEL_MEDIA_COMMAND_PLAY]);
            }
        }
        
        // now check if we have an agent in the list, who's not been detected
        
        integer l = llGetListLength(gCurrentAgents);
        
        for(i=0;i<l;i++){
            
            integer pos = llListFindList(presentAgents, [llList2Key(gCurrentAgents, i)]);
            
            if(pos == -1){
                // This agent is gone - stop the Stream for her/him/it
                llOwnerSay("removing " + llKey2Name(llList2Key(gCurrentAgents, i)) + " from the list");
                llParcelMediaCommandList([PARCEL_MEDIA_COMMAND_AGENT, llList2Key(gCurrentAgents, i), PARCEL_MEDIA_COMMAND_STOP]);
                // Remove the Agent from the present list
                gCurrentAgents = llDeleteSubList(gCurrentAgents, pos, pos);
            }
        }
      }
      
        no_sensor(){
            // There are no more Agents present. Try to stop all streams for the Agents in the list
            
            integer l = llGetListLength(gCurrentAgents);
            integer i;
            
            for(i=0;i<l;i++){
            
                // This agent is gone - stop the Stream for her/him/it
                llOwnerSay("removing " + llKey2Name(llList2Key(gCurrentAgents, i)) + " from the list");
                llParcelMediaCommandList([PARCEL_MEDIA_COMMAND_AGENT, llList2Key(gCurrentAgents, i), PARCEL_MEDIA_COMMAND_STOP]);
            }
            
            // Remove all agents from the list
            
            gCurrentAgents = [];
        
        }
}

The problem was, that when only one agent was detected, this agent never got deleted from the list, since I forgot to put in a no_sensor-event.

There were some other bugs as well, one, that I didn't mention the texture in the parcel-media-command-list.
The «trick»*that is used here is, that we use the video-channel to play mp3-files (which works pretty well). There's one quirk with that. You have to edit your land-info, go to the media-tab and check the box «Media -> Auto-Scale». If you don't do this, it might not work...

I added some «llOwnerSay»-commands to the code so you can see whether the agent is added or deleted from the list. Once everything is working, you can delete those lines. If you are on group-owned land and have to deed the object to make it work, change those llOwnerSay into «llSay(0, ...)», because you won't hear llOwnerSay-messages from a deeded object...

Hope it works...

Cheers

H

P.S. no - pun intended - but the name «Doug» always remembers me of Gary Larson's Farside (beware of Doug) http://farm1.static.flickr.com/27/58683157_cf923d8f56.jpg?v=0

Hi Haruki,

Thanks so much for this! It works like a charm.

I have a question though - why do you use the video channel to play mp3 files? Why not just use:

PARCEL_MEDIA_COMMAND_TYPE, "audio/mpeg" ?

Anyway - thanks again for all your help with this. It is a huge help to me and my students will appreciate it.

BTW, I have that picture on my bulletin board above my desk at work, along with these two.

http://obgyn.osu.edu/images/Doug-1.jpg
http://obgyn.osu.edu/images/Doug-2.jpg

Take Care,

Doug

Hi Doug

Now that I read the manual of the Parcel-media-command again, I'm asking myself the same question... Seems like you pointed me to something here... Ah well... I should read manuals more thouroughly...

Glad' it's working now, though

Happy Farside!