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Thread: HTTP download speed of video segments

  1. #1

    Default HTTP download speed of video segments

    I'm using wowza for HLS streaming and was comparing its performance versus using an HTTP Server (IIS). I have Wowza and IIS setup on the same box. I encoded a video into 6 bit rates using Compressor's default settings for HLS, and I had it also segment those videos out. I uploaded everything into a single folder and pointed IIS and Wowza at it. They both play really great, but when playing the video via IIS it starts and seeks way faster than from Wowza. At first I thought this might be due to the fact that Wowza has to create the manifest files and segments on-the-fly, but that's not the issue. When I watch the HTTP traffic, the segments are downloaded significantly quicker from IIS than from Wowza. Is that to be expected? Or is there some type of throttling going on in wowza that I can control?

    The pre generated segments being served by IIS are about 6.2MB each. They get delivered in roughly 1.8 seconds.
    The segments served by wowza are about 5.6MB each. They get delivered in roughly 3 seconds.

    I would think that wowza should be able to read and output the data as quickly as a web server. Also, I do understand that wowza is doing a lot more work than the webserver in that it needs to seek to the correct spot to create the segment, but that doesn't seem to be the issue. The actual download is just slower...

    Thoughts?

  2. #2
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    Hi Sean,

    Chunks are sent to playback clients as fast as the network between Wowza and the client will handle. These chunks are not throttled. RTMP streaming is throttled, but it is not necessary in HTTP streaming.

    Richard

  3. #3

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    Hmm, if that's the case I would expect wowza to deliver the chunks as quickly as IIS. Any theory as to why wowza would be slower? Is there any throttling going on when wowza reads the file perhaps?

  4. #4

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    What if you put Varnish Caching Server in front of Wowza and measure the speed. I use Varnish to cache the HTTP Streaming and woul like to know the HTTP Segment Download Speed too

    https://www.varnish-software.com/blo...eaming-varnish

  5. #5
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    Wowza packetizes the live stream as it comes in. It's not throttled, but can only packetize as fast as the stream is received.

    Richard

  6. #6

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    Quote Originally Posted by rrlanham View Post
    Wowza packetizes the live stream as it comes in. It's not throttled, but can only packetize as fast as the stream is received.

    Richard
    Hi Richard, I'm dealing with VOD playback not live streams. As mentioned in my original post, I have wowza and IIS both running on the same machine. Wowza is pointed to one set of encoded files, while IIS is pointed to the segmented versions of the files wowza is pointed at. IIS transfers the segments considerably faster than wowza. I don't see why wowza would be slower in this operation.

    Sean

  7. #7
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    Sean,

    Sorry, somehow I got the idea you were comparing live. With vod there is little delay in packetizing. As far as I know there is no throttling of chunks, they are going to get to the player as fast the network can handle it. There is probably some other difference in the comparison.

    Richard

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