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Thread: Smooth streaming question

  1. #1

    Default Smooth streaming question

    Hi!

    We would like to record the output of the transcoder which publishes 5 streams for smooth streaming. Those recorded streams at some later date would need to be made available again on a live application. Can that be done? How? The first question is how to achieve key frame aligned recording and the second, how to make key frame aligned playback from the recorded files.

    Thanks!
    Atmapuri

  2. #2
    Join Date
    Jun 2012
    Posts
    723

    Default

    Hi,

    If you are using the Transcoder addon to transcode your input stream into multiple streams using different encoding profiles, then those stream will be properly key-frame aligned. Since the streams are key-frame aligned, also the recording will also have the key-frames properly aligned.
    In order to play back these recordings using Wowza, you will need to create a VOD type application (not Live) and provide those recordings for adaptive bitrate streaming using a .smil descriptor file, as described in the "How to do adaptive bitrate streaming" forum article.

    To record a live published stream (the Transcoder outputs as well), please take a look at the instructions described in the "How to record live streams (Wowza Streaming Engine)" forum article.

    If you do want to provide these recording as a simulated live stream, then you can create a server side scheduled playlist, that would start a live stream by playing back, at a scheduled time, a list of your VOD recordings. You can follow the instructions described in the "How to do scheduled streaming with Wowza Streaming Engine (StreamPublisher)" forum article in order to implement this workflow.
    In particular, you can take a look at the "How to do scheduled, adaptive bitrate streaming using Stream class streams" forum article as well.

    Zoran

  3. #3

    Default

    Dear Zoran,

    The request is to put the recorded streams back in to another live application, not VOD.

    Also: How do you make frame aligned recording on the Wowza server of 5 streams? if you I do it via user interface, the recordings start at different time, because there is no way to press "record" concurrently for all.

    Thanks!
    Atmapuri

  4. #4
    Join Date
    Jun 2012
    Posts
    723

    Default

    Hello,

    You cannot have VOD assets delivered using a "live" stream type application.

    Regarding your second remark, you are correct. It wouldn't be efficient to record using the Wowza Manager user interface. You can develop a custom Wowza module and record your transcoded streams programatically, as described in the "How to record live streams (HTTPLiveStreamRecord)" forum article, in the "Recording live streams programmatically" section.

    Also, you can generate multiple renditions of a recording, having the VOD assets properly key frame aligned by using FFMPEG. Please take a look at the following forum thread for an example on how to use FFMPEG to generate key-frame aligned VPD files: http://www.wowza.com/forums/showthre...ples-for-Wowza

    Zoran

  5. #5

    Default

    Dear Zoran,

    >You cannot have VOD assets delivered using a "live" stream type application.

    You have mentioned (StreamPublisher) before so it is possible. The example is not very convincing. Cleary the playback
    will start at the same time, but in separate threads. What is the mechanism to ensure that alignment is accurate
    to one frame, because individual streams do not seem to know about each other?

    >Regarding your second remark, you are correct. It wouldn't be efficient to record using the Wowza Manager user interface.
    > You can develop a custom Wowza module and record your transcoded streams programatically,

    How can I ensure they are recorded exactly concurrently (down to the last frame)?

    >Also, you can generate multiple renditions of a recording, having the VOD assets properly key frame aligned by using
    >FFMPEG. Please take a look at the following forum thread for an example on how to use FFMPEG to generate key-frame aligned VPD files:

    This does not help, because the point of reusing transcoded files is to save the CPU usage.

    Thanks!
    Atmapuri

  6. #6
    Join Date
    Dec 2007
    Posts
    21,962

    Default

    Atmapuri,

    What you describe at top wikk work. The Transcoder renditions are key frame aligned, as Wowza Transcoder feature, and the recordings should be key frame aligned for later vod abr delivery, or for scheduled live abr streams

    Richard

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