Palavatv works in local lan, but not in internet

[VosaXalo]

I have tried palava.tv with two PC that are identical:

• OS: Ubuntu 12.04 64bit
• Browser: Chromium version 31

The first time the two PC were connected on the same network. I mean that the two PC were connected to the same router, in other words on the same local network. In this case the audio and video conference has worked perfectly.

The second time the two PC were connected to the internet with two distant routers (as is the common situation between users on the net). In this case I can't see the other person, but only a black rectangle, or a rectangle with a black dot in the middle. The video doesn't work, nor the audio.
It seems that something is wrong with the routers?, the firewalls?, router ports? It's strange as palavatv it'a a web page.

If this can help I have copied and pasted here some console messages from the browser during the second test (the two PC connected to different routers):
DEBUG
Arguments[1]
all-767cd71c.js:27
DEBUG
Arguments[2]
all-767cd71c.js:27
DEBUG
Arguments[2]
all-767cd71c.js:27
event.returnValue is deprecated. Please use the standard event.preventDefault() instead. jquery.min.js:16
DEBUG
["peer stream removed", RemotePeer]
all-767cd71c.js:27
DEBUG
["peer left", RemotePeer]
all-767cd71c.js:27
DEBUG
["peer joined", RemotePeer]
0: "peer joined"
1: RemotePeer
$$hashKey: "00G"
_events: Object
distributor: Object
getStream: function (){ return fn.apply(me, arguments); }
hasAudio: function (){ return fn.apply(me, arguments); }
id: "0c4deab7-3616-4598-ab34-a7f8a2dead68"
isLocal: function (){ return fn.apply(me, arguments); }
isMuted: function (){ return fn.apply(me, arguments); }
isReady: function (){ return fn.apply(me, arguments); }
joinTime: 1390140408573
local: false
mozillaCheckAddStream: function (){ return fn.apply(me, arguments); }
muted: false
oaError: function (){ return fn.apply(me, arguments); }
peerConnection: RTCPeerConnection
ready: true
remoteStream: MediaStream
room: Room
sdpSender: function (){ return fn.apply(me, arguments); }
sendAnswer: function (){ return fn.apply(me, arguments); }
sendOffer: function (){ return fn.apply(me, arguments); }
sendOfferIf: function (){ return fn.apply(me, arguments); }
setupDistributor: function (){ return fn.apply(me, arguments); }
setupPeerConnection: function (){ return fn.apply(me, arguments); }
setupRoom: function (){ return fn.apply(me, arguments); }
status: Object
toggleMute: function (){ return fn.apply(me, arguments); }
proto: ctor
callee: function (){return t.log("DEBUG",arguments)}
length: 2
proto: Object
all-767cd71c.js:27
DEBUG
["peer stream ready", RemotePeer]
0: "peer stream ready"
1: RemotePeer
$$hashKey: "00G"
_events: Object
distributor: Object
getStream: function (){ return fn.apply(me, arguments); }
hasAudio: function (){ return fn.apply(me, arguments); }
id: "0c4deab7-3616-4598-ab34-a7f8a2dead68"
isLocal: function (){ return fn.apply(me, arguments); }
isMuted: function (){ return fn.apply(me, arguments); }
isReady: function (){ return fn.apply(me, arguments); }
joinTime: 1390140408573
local: false
mozillaCheckAddStream: function (){ return fn.apply(me, arguments); }
muted: false
oaError: function (){ return fn.apply(me, arguments); }
peerConnection: RTCPeerConnection
ready: true
remoteStream: MediaStream
room: Room
sdpSender: function (){ return fn.apply(me, arguments); }
sendAnswer: function (){ return fn.apply(me, arguments); }
sendOffer: function (){ return fn.apply(me, arguments); }
sendOfferIf: function (){ return fn.apply(me, arguments); }
setupDistributor: function (){ return fn.apply(me, arguments); }
setupPeerConnection: function (){ return fn.apply(me, arguments); }
setupRoom: function (){ return fn.apply(me, arguments); }
status: Object
toggleMute: function (){ return fn.apply(me, arguments); }
proto: ctor
callee: function (){return t.log("DEBUG",arguments)}
length: 2
proto: Object

[beyondthewall]

i experience the same. video/audio is only possible when a direct ip communictaion can be established. which is not possible behind two nat routers.

[VosaXalo]

I have tried to start a conference between my Android smartphone with Google Chrome, and my PC with Ubuntu 12.04 and Chromium installed, but the issue is the same. I can't view, nor near, the other person. The problem is identical as the one with the two PC connected to the net as I explained above.