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Thread: VODS3 +, Number(uv.skip)); = long loading time?

  1. #1
    Join Date
    Jul 2013

    Default VODS3 +, Number(uv.skip)); = long loading time?

    Hi All,

    I'm using the default VODS3 application combined with wowza server running on EC2, this is working great until I want to skip the first part of a video.

    For example, I decide I want to skip the first 600 seconds from my video file and start playing from second 601. The code I use for this in the flash client is:, Number(uv.skip)); In which uv.skip indicates the number of seconds I would like to skip.

    This works with VODS3, but the first time it always takes a very long time to load. The higher I make the skip value, the longer it takes to load. So it seems that the video isn't really "skiped", but the player just waits until all the data before skip is loaded and then starts playing.

    Some time I play larger files (I've tested with a 42 minute, 172 MB file) and if I choose to skip the first 30 minutes (1800 seconds) than the loading time can take up to over 1 minute, which offcourse is unacceptable for any customer .

    The second time I load this video the loading time is very fast (1 second), but as soon as I change the skip value again to for example 25 minutes it takes over a minute to load again.

    Any advice on how to solve this?

    Many thanks,

  2. #2



    What you are describing sounds like the wowza server is having problems communicating with S3 rather than a player implementation problem.

    With VODS3, Wowza uses MediaCache to communicate with Amazon S3 over http. When a file is requested, it should only request the chunk of the file from the point where you specify. It doesn't read from the beginning of the file up to that point. This is confirmed in your last sentence where it takes a long time for the first request but the second request for the same point is fast. This is because the MediaCache is storing the chunks locally. Changing the start point to beforehand results in a slow request again because that chunk is not already cached.

    Are you using one of the Wowza amis? or are you using your own configuration?
    Have you modified any settings to do with the Mediacache or the VODS3 application?
    Where is the S3 located compared to the Wowza server?


  3. #3
    Join Date
    Jul 2013


    Hi Roger,

    Thanks for your response. I agree with you that the delay probably is caused by slow communication between Wowza and Amazon S3.

    To answer your questions:
    - I'm using a default wowza AMI from the official wowza website.
    - I did not modify any settings that relate to Mediacache or VODS3 (only using modulesecuretoken and modulehotlink)
    - Both S3 and Wowza (EC2) are located in Ireland, and I'm located in Europe as well (Belgium), with a very highspeed connection.

    Can you give any more advice?

    Many thanks,

  4. #4


    Hi Henkhenk,

    I have been working and tuning MediaCache configs for a year now and I can tell that some delays for retrieving the data at first play from the HTTP source is within expected behavior. I have seen case where it could take 15-30 sec to launch a video at first play depending on the network conditions. As mentioned Roger MediaCache is only retrieving chunk of the mp4/flv files that are requested for streaming but still it could need some time to get those chunks from the HTTP source and package them for streaming on the EC2 Wowza Media Server (this is at first play ... MediaCache hits its full potential when serving contents from its local cache). Here are a couple of things you could try/check:
    - Try to set up your Wowza EC2 with the basic vod application (so that content could be stored directly on the EC2 instance) and see if you still have the same issue.
    - If you are willing to dig further into the mediacache add on you could open MediaCache.xml and define a new <MediaCacheSource> and see if you still experience significant delays for seeking into the video (like one of your web server you may have on hands that is not hosted within Amazon). You can find documentation on this by requesting the full MediaCache module here After that you could fine tune values in MediaCache.xml like <DefaultBlockSize> or maxPoolSize property (increase values) or ReadAheadThreshold (decrease values).
    - If streaming mp4s make sure your mp4s have aligned keyframes and that the interval between those keyframes is not too big (we use 2 sec interval)
    - Eventually you may consider scenarios where you could want to "pre-heat" some hot items in your MediaCache before they hit your customers (playing them in full before hand)

    Streaming Engineer

  5. #5


    Hi Henkhenk,

    Which AMI are you using? If it is a older one, there have been changes to the MediaCache recently that may not be on you AMI.

    I would like to do some testing to see if we can replicate what you are seeing. Could you open ticket at and reference this post. We would need details of the AMI that you are using and your configuration and logs. Please zip up the conf & logs folders from your EC2 instance and include in the ticket. If possible, could you also include a download link for an example file that we can test with. It is best to use the same files that you are experiencing problems with.



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