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Thread: I find variances in Livestream vs Wirecast experience playback

  1. #1
    Join Date
    Feb 2014
    Posts
    129

    Default I find variances in Livestream vs Wirecast experience playback

    I was wondering if anyone can suggest what might be the reason for the following,

    Doing a live stream with a constant application variables I test 2 encoders. wirecast and livestream studio. I am using the Wowza Transcoder option and my highest quality stream is the "source", then I have 2 lower quality varients from the transcoder.

    I am playing the stream in a Silverlight player from Expression encoder on my webiste.

    I find that when using the wirecast encoder that the streams I view do not reliably switch and also the player seems to not find the bandwidth as good as when using the Livestream Studio encoder. Since they both are set at the same output bit rates I don't understand why Livestream encoding generates a much better viewing experience

  2. #2

    Default

    Hi,

    Look at the key frame intervals that both encoders set. I am not sure about the LiveStream encoder but I know that WireCast sets the key frame interval every x frames so relies on the frame rate to be constant. This is in contrast to other encoders that will insert the key frames at specific time intervals.

    With that in mind, also make sire the frame rates are the same.

    In your transcoder templates, make sure you have KeyFrameInterval > FollowSource set to true for all of your encodes.

    Roger.

  3. #3
    Join Date
    Feb 2014
    Posts
    129

    Default

    Ahh yes, thank you
    The key frame interval in Wirecast defaults to a multiple of 30, so when I change the frame rate to 25 I should have changed key frames too. It looks like this has made it better.
    Not sure what the best number is though, it was 240 or 8 seconds at 30fps, is this the norm at 8 seconds? ~ 200 key frames for 25fps

  4. #4

    Default

    Hi,

    For silverlight, you should have a key frame interval between 1 & 4 seconds so at 25 fps, this would be between 25 & 100.

    You will see a warning in your server logs if the key frame interval is outside this range.

    Roger.

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