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Thread: Latency

  1. #1
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    Latency

    using fl3 + fcs3
    trying to receive live video on S60/N95
    WITH THE MINIMUM LATENCY
    I'm unable to obtain less than 2 seconds !

    Any suggestion ?????

  2. #2
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    Re: Latency

    2 seconds sounds quite good to me?
    Mark Doherty
    Developer Evangelist
    Adobe Systems, Mobile and Devices EMEA

  3. #3
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    Re: Latency

    I agree, if you are talking about the time it takes to start playing the video after "the phone has been instructed to start streaming it".

    Hartti

  4. #4
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    Re: Latency

    in a remote control context
    2 seconds is too long !

    we don't speak about streaming
    (buffering THEN playing)
    but real time video connection
    (minimum buffer)

    so, same question :
    is there any solution using fl3
    compliant with low latency ?

  5. #5
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    Re: Latency

    Unless you leave a permanent connection open I can't see how this is achievable with any wireless technology. Even if you had all the power and resources of a laptop you would still have to wait until the network serves the stream.

    You could potentially have video channels loading and buffering off stage and simply move between channels by moving movieclips, though the startup time would be large.

    Another out of the box idea would be to create a new channel that has each video in a grid. You could possibly just mask out the channels that you don't want the user to see.

    Again these are extreme and even with a high end S60 device I imagine the available memory would become an issue.
    Mark Doherty
    Developer Evangelist
    Adobe Systems, Mobile and Devices EMEA

  6. #6
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    Re: Latency

    Are you testing the latency with a wireless broadband network or 3g/3.5g connection?

    I've found 3g network latency and speed is pretty variable so always test with wireless.

    Also, what are you trying to change exactly? There maybe something you could optimise better, maybe server-side, if we know what the changes are that you need.

    Cheers

    Nick
    http://www.flashcell.com
    http://www.device54.com

  7. #7
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    Re: Latency

    The target network is 3G
    Right now, we are working over wlan
    The latency > 2sec is measured over wlan
    This wlan is dedicated :
    1 PC client + 1 PC server (fcs3) + 1 N95 8G
    To obtain the lowest latency, I have tried to decrease video size, video quality, keyframerate, framerate and buffer size.
    Am I wrong when I say :
    no way to obtain something near 200ms total latency ????
    Does anybody have an idea about the minimum latency (in a best protected wlan environment) we could REALLY obtain ?

  8. #8
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    Re: Latency

    In a unconstrained bandwidth situation you should acheive less than 2 seconds thats for sure. I would have thought 500/ms is acheivable but you still haven't said what exactly you are trying to do? Are you seeking, switching feeds, making netStream calls, etc?

    Also it goes without saying you should have a buffer of 0 if you want fastest response time in changing a stream. Also reducing the number of keyframes won't actually help you in terms of starting a stream quickly.

    Also when you say latency ....at what point are you measuring it? assume you are measuring it after you have established a succussful connection to Media Server?


    Cheers


    Nick
    http://www.flashcell.com
    http://www.device54.com

  9. #9
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    Re: Latency

    Application :
    remote control with video feed-back
    One way video (Rx)
    No switching between streams.
    No constraint concerning the start-up delay
    (connection to server + decoder launching)

    At this stage, the latency is "poorly" evaluated
    - connection established, video displayed
    - starting a digital chronograph
    - shooted by the camera

    No need for more acurate measurement as long as I have not obtained less than 1sec.

    For my point of view,
    less keyframes = less bandwidth (better)

    in fact,
    movement restitution is targeted
    more than video quality.

  10. #10
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    Re: Latency

    Quote Originally Posted by testN95_ View Post
    remote control with video feed-back
    Ok so live video fed by user interaction on the client, thats nice to know!

    Be very useful to findout the exact points of latency, as there are at least 3 ro 4 processes I would have thought as well as 2 client to server trips!


    Quote Originally Posted by testN95_ View Post
    For my point of view,
    less keyframes = less bandwidth (better)
    yes, now I know what you're doing its not relevant, it may have been for switching streams.

    Is your latency issue Flash Lite specific? I'd test in browser with Flash 9 first as a benchmark. Get that to perform then move to mobile. Should be easy to do.


    is it similar to : http://blog.jaycharles.net/?p=20


    Cheers


    Nick
    http://www.flashcell.com
    http://www.device54.com

  11. #11
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    Re: Latency

    The PB is flashlite specific.
    I have tried different configuration :
    - fcs3 + 2 clients
    - red5 + 2 clients
    - ffserver + 1 client
    Same result.

  12. #12
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    Re: Latency

    All I have seen concerning RC is local :
    i/e bluetooth, wifi or IR link
    with the RC model near the telephone.
    As I mentioned, our context is remote
    i/e long distance between model en phone.
    The wlan context we are discussing about
    has been used to try to understand if we can use fl3 in place of a 3G video call.

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