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Participating Frequently
April 22, 2008
Question

live stream sample with big delay

  • April 22, 2008
  • 2 replies
  • 1680 views
Hello,

some days before we started evaluation of the flash media development server for windows. All live video stream samples taken from adobe media encoder (320x200, VP6, std bitrates) seem to have big delays up to 2 or 3 seconds on the client flash player. I think this is a "little bit" too much when server and client are running on the same local host.
As soon the connection to the source stream is established the stream starts on the client without any delay BUT it starts with frames from >=2 seconds before.
So there seems to be a problem on the server that caches too much data from the media encoder source before sending it to the client. I modified the MinBufferTime in the related live Application.xml file to 200ms instead of 2000ms but nothing changed. Maybe for some unknown reason those settings are ignored because I also tested 8000ms and I also tried to modify the gloabal Application.xml of the virtual host but there is no difference. I always get those big delays and it gets worse if I also stream audio data.

I tried it on two different computers with the current FMS release but the delay occurs on both platforms. I searched in several fms & flash boards but there seems to be no user with the same problem.

What's wrong? Any ideas?

MfG
Robin Siegemund
    This topic has been closed for replies.

    2 replies

    April 23, 2008
    Apart from other factors, Live aggregate messages which enhance the FMS throughput bandwidth @ given-CPU-usage contribute somewhat to this fix delay.

    Delay in audio reduces to almost zero if we set:
    <Live>
    <Queue enabled="true"> to <Queue enabled="false">
    </Live>

    - Probably, it results into too much performance penalty.
    - Additionally, only disabling live aggregate messages might have some benefit with somewhat less performance loss.
    dpRobAuthor
    Participating Frequently
    April 23, 2008
    Thanks for reply.

    I modified the the live queue to "false" but I still have big latency. At begin of transmission I have a delay of a second and after a minute or so it increases to 2 seconds.

    I still have the feeling something goes extremely wrong here...
    Maybe I've time to test some other flash-capable products like Red5 to see if there's a difference but I hesitate to install all that tomcat stuff.

    Sincerely,
    dpRob
    Known Participant
    April 23, 2008
    It sounds like a similar issue I ran into. It turned out to be a client issue. Did you try explicitly setting buffer time to 0 on the client end?
    April 23, 2008
    I don't think it is unusual to have 1-2 second of delay while publishing through FME (which is a CPU intensive task and introduces a minimal leg).

    Still you might want to tweak with <Live><queue> </queue></Live> settings in \conf\_defaultRoot_\_defaultVHost_\application.xml but that risks fiddling with the optimal configuration for performance FMS3 comes with.
    dpRobAuthor
    Participating Frequently
    April 23, 2008
    I've tested it on 3 different machines now including current core 2 duo dual core CPUs and plenty of RAM, 1Gbit network, etc.

    I also tested Adobe's Acrobat Connect conferencing software and interestingly here I have found the same issues.

    But after some tests I can isolate the problem more specifc: The audio transport is the big problem maker and not the video part.

    If I switch to video only: It's ok. But if I switch to video+audio or AUDIO ONLY (even at very low bitrates) I have delays with at least 1.5 seconds.

    I've tested it on different machines and sound cards but it's still the same issue. So what could be the reason why only audio leads to such big delays??

    dpRob