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Thread: Latency problem-Why video has better performance than audio

  1. #1

    Default Latency problem-Why video has better performance than audio

    We delveope a video conference system.

    Thanks for Richard. I read many of your post and fixed a lot of issues.

    When we have good network connection on internet, we sometimes can have less than 1 sec latency of audio .

    When we got low bandwidth , we had 3-4 seconds latency of audio(round trip). But video always come first about 2 seconds than audio. It's strange. I think video require much more bandwidth than audio. I'm wondering why video get better performace than audio.

    Server will drop some audio package when the network connection is poor. I won't hear audio from otherside for a few seconds.

    When we use udp to transport audio in our previous software, we will get a borken voice when bandwidth is low. When we use Wowza, it will drop a lot of package. it's not very good. I really doubt if we can get a good audio quality on tcp connection.

    Can we do better about audio latency problem? Can we achieve more stable audio quality? thanks for any suggestion

    We totally adhere to the video chat example Richard recommended to set up everything in our code.

    Below is now setting on Apllication.xml

    <Property>
    <Name>maxliveaudiolatency</Name>
    <Value>1000</Value>
    </Property>
    <Property>
    <Name>instantOn</Name>
    <Value>false</Value>
    <Type>Boolean</Type>
    </Property>
    <Property>
    <Name>flushInterval</Name>
    <Value>25</Value>
    <Type>Integer</Type>
    </Property>
    <Property>
    <Name>onFlushNotifyClients</Name>
    <Value>true</Value>
    <Type>Boolean</Type>
    </Property>
    <Property>
    <Name>disableLowBandwidthThrottling</Name>
    <Value>false</Value>
    <Type>Boolean</Type>
    </Property>
    <Property>
    <Name>behindDropDFrames</Name>
    <Value>1000</Value>
    <Type>Integer</Type>
    </Property>
    <Property>
    <Name>behindDropPFrames</Name>
    <Value>2000</Value>
    <Type>Integer</Type>
    </Property>
    <Property>
    <Name>behindDropKFrames</Name>
    <Value>3000</Value>
    <Type>Integer</Type>
    </Property>
    <Property>
    <Name>behindDropAudio</Name>
    <Value>1000</Value>
    <Type>Integer</Type>
    </Property>
    <Property>
    <Name>isLive</Name>
    <Value>true</Value>
    <Type>Boolean</Type>
    </Property>
    Last edited by jiwan2004; 03-01-2012 at 07:27 AM.

  2. #2
    Join Date
    Dec 2007
    Posts
    21,962

    Default

    Where do you have these Property settings? They should be in /conf/[application]/Application.xml /Streams /Properties list.

    If the client's bandwidth is lower than the bitrate of the stream there will be playback problems, and there really isn't anything you can do about it except reduce the bitrate, which is probably low to begin with in a chat app.

    Richard

  3. #3

    Default

    We set these properties both in application.xml and streams.xml. I use live-lowlatency type. Properties in applicatioin.xml will overwrite all properties for all stream type.

    I'm wondering why video has no latency but audio has. When bandwidth is low , users would rather have good audio quality .

  4. #4

    Default

    By the way, we suggest to select default codec. We select a codec recommended by adobe ar first. But we find it will grow latency with the meeting going on. The properties in streams.xml don't work. After we have changed to the default codec , it works fine. The server start to drop the package when the bandwidth is low

  5. #5
    Join Date
    Dec 2007
    Posts
    21,962

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    Those Property settings will override Property settings in Streams.xml if they are place in the Application.xml /Streams Properties list, not the Properties list at bottom of Application.xml

    If you can can require Flash 11, you can use h.264 video and Speex audio. That should improve quality. This article shows how to set that up:

    http://www.wowza.com/forums/content....across-clients

    Richard

  6. #6

    Default

    Thanks,Richard. We have tried Speex audio before in flash 10. It doesn't work. The Wowza server didn't drop any package which cause growing latency.

    I have read the link you posted. Before we didn't make any change of configuration on the server . Is it reason why it's doesn't work ?

    Can we use Speex audio in Flash 10? It's difficult to require users to update software.

    Thanks

  7. #7
    Join Date
    Dec 2007
    Posts
    21,962

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    Yes, Speex audio is supported in Flash 10, but not h.264 video

    Richard

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