WMV vs ASF as streaming video

Discussion in 'Windows Media Player' started by liu, Apr 2, 2009.

  1. liu

    liu Guest

    The manager of our intranet team insisted that only ASF is streaming
    video while WMV progressive. What are the differences between the 2
    formats? What are the benefits of using one over the other with Media
    Service of IIS?

    I thoguht ASF is an older format while WMV newer. You can actually
    rename extensions either one to the other and it still plays. Is there
    MS literature describing the right format to use under different
    conditions?

    Thanks for the help,
     
    liu, Apr 2, 2009
    #1
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  2. He's mistaken then. Insisting doesn't make him any more right.


    ASF and WMV are both video containers (call them file formats for
    simplicity). ASF can contain multiple video types, and video+audio or
    just audio (but is most often WMV).

    WMV is a specific case of ASF that contains only windows media video +
    audio. WMA is ASF which contains only windows media audio.


    The file format is completely unrelated to the delivery format. You
    can 'stream' any content, and you can progressively download any
    content.

    Typically - though not always - progressive download is not
    restartable or seekable. The client has to wait for the download to
    reach a "seek point" before it can be played.

    By streaming, we mean the player sends instructions to a media server
    to seek, and the seek is done at the server end with negotiation to
    manage the 'gap'. This usually results in a (very) short pause in the
    player as it fills its buffer from the new data the server is sending.

    IIS7 has a smooth streaming extension which is able to manage
    stream-switching, I think there's some seek capability as well.

    That's not available in media player though, which predates IIS7 - so
    you'd have to use a Silverlight media control to play nice with that,
    or use WMS9 with windows media player.

    You might need to consider your audience carefully if you're using
    IIS7 smooth streaming compared to progressive download. As noted,
    you'll need Sillverlight on each PC, which might not be permitted by
    corporate IT policy.

    With IIS6 you would only have progressive download, but on a fast
    intranet the seek time might not be a problem and it could come close
    to streaming experience.

    If you have lots of people at branch offices controlled by a private
    corporate network watching the video (say a live stream) you might
    want to look at Multicast between sites, to minimise the bandwidth
    sent over the WAN (this requires media services, and can't be done
    with a web server of any type)

    Oh, and web servers don't do live streaming at all, at least not
    without some staggeringly complicated hacks and scripting.

    HTH
    Cheers - Neil
     
    Neil Smith [MVP Digital Media], Apr 5, 2009
    #2
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  3. liu

    liu Guest

    Thanks a lot for the explanation.

    I think we use only Media Services of IIS. I will ask him about smooth
    streaming extension.
     
    liu, Apr 10, 2009
    #3
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