NetGroup multicast: delay, a/v out of sync

Question

Hello,
I've tested multicast example Michael provided us with (viewer.mxml/provider.mxml) and found that after viewer is connected there is a significant delay between publisher and viewer (around few secs) that is being reduced till realtime in some time, but even after delay is reduced we have audio/video out of sync, sound came later than video (or maybe video came later than audio... don't remember exactly).
Do you have any ideas why this happens - maybe because of beta?

Answer 1

Hi Mike,
I'm back with more details. I tried publishing with a Mac instead of a Windows but still having the same problem. I tried out  VideoPhoneLabs live sample to test 1-1 communication and observe A/V  sync. Everything is working fine (but VideoPhoneLabs isn't using NetGroups multicast). I tried out publishing/subscribing on the same computer but doesn't make any difference. Still getting the same problem with audio so I tried out creating an application using only audio stream. Here are the details of my application:
- I created a conference call application (uses only audio streaming) where all participants are allowed to speak and hear other participants.
- Here is how it works:
     - First I create a NetConnection and connect to Stratus with "rtmfp://stratus.adobe.com/" and my developer key (Connection without out any problems).
     - Once connected to the server, I create my GroupSpec with the following options:
                _groupSpecifier = new GroupSpecifier( GROUP_NAME );
                _groupSpecifier.multicastEnabled = true;
                _groupSpecifier.objectReplicationEnabled = true;
                _groupSpecifier.postingEnabled = true;
                _groupSpecifier.routingEnabled = true;
                 _groupSpecifier.serverChannelEnabled = true;
                _groupSpec = _groupSpecifier.groupspecWithoutAuthorizations();
     - Then I join the NetGroup and initialize my outgoingStream at the same time.
     - Once "NetStream.Connect.Success" is dispatched, I start my outgoingStream:
               - I attach the audio to the stream (I use "mic.codec = SoundCodec.SPEEX")
               - I publish it using "_outgoingStream.publish( _netGroup.convertPeerIDToGroupAddress(_nearID) )"
     - To listen to other participants stream, I listen to the event "NetGroup.MulticastStream.PublishNotify". Once this event is dispatched, I create as many incoming streams as participants joining the same group. If you need more details on how I create these incoming streams, I'll be happy to communicate them to you.
     - Everything goes fine, I can see all participants connected to the group and hear them all BUT here is my big problem. When participants are speaking there is an audio latency of 2-3 seconds before I can hear them (test based on "OK" written in SKYPE when a participant starts speaking). All participants have to wait about 20-30 seconds before a complete synchronization, meaning no latency on audio. Participants speak and are heard straight away. After these 20-30 seconds synchronization, communication is just amazing. Everything is perfect.
     - I tried this application on the following environment: every participants are publishing/subscribing using either Mac, Windows Vista, Windows 7 on either FireFox, Google Chrome or Safari. I tried it out as well just on my Windows 7 (publisher and subscriber) using several different browsers (to simulate other participants) but still getting the same problem (audio latency of 2-3 seconds and after 20-30 seconds, synchronization is perfect). Did the same again but just on one Mac but still the same problem.
I hope my explainations are understandable. My goal is to reduce these 20-30 seconds before synchronization is good (no latency).
I think the problem is comming for the audio, because video is usually working great. It maybe comes from the fact I'm using NetGroup because 1-1 communication using VideoPhoneLabs (which is not using NetGroup... tell me if I'm wrong) and other application I've created before based on VideoPhoneLabs are working greate (no latency).
I really can't get over this problem. Hope to hear from you soon.
Sincerely
-suiss