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Thread: Transcoder plus VOD injection not recording properly

  1. #1

    Default Transcoder plus VOD injection not recording properly

    I am send a live stream via Flash webcam using H264/Speex. I am then transcoding this live signal using the audioonly.xml transcode profile to generate a separate stream that is now H264/AAC. Then I am using HTTP request to record the new H264/AAC stream on the Wowza Server, which is working fine.

    The problem I'm having is that I am also injecting VOD into the live stream in real-time. The VOD is already in H264/AAC format. When I switch from the live webcam feed to a VOD, I can see it just fine when I'm watching live. However, the recording on the server does not record the VOD inject properly. It only shows black, sometimes noise and no movement.

    I don't see this problem if I use an external encoder sending H264/AAC and if I don't use the transcoder. Please let me know why I can't inject VOD in a live stream and have it record properly, even though I'm using the transcoder to generate the same video/audio codec pairing.

  2. #2

    Default

    I am not 100% sure what you are trying to do here.

    But the Wowza Transcoder does not support VOD as input. You can use Stream Class Streams to send a "live" stream to the Transcoder using static content(file) by following this guide:
    How to do basic server-side publishing with Stream class streams

    And for switching the stream sources, please take a look at this guide:
    How to switch streams using Stream class streams

    Salvadore

  3. #3

    Default

    I am doing just as you described in the docs - I am using the Stream Class to switch between a live source (my webcam) and a VOD (h264/aac) file as a live stream . Then I have the transcoder enabled on that Application.xml file using audioonly.xml. The reason I have audioonly.xml transcode template enabled is because my webcam is sending H264/Speex (Flash has no support for AAC) so all I need is the audio to be transcoded.

    Wowza then generates a new stream for me called <streamName>_aac. If I view this on my Android phone, all is well - until I use the Stream class to switch to the VOD file source in the live stream. That's when the video gets all noisy and jumbled and the audio is all noisy also. If I then switch back to my webcam, the feed looks as it should.

    I'm wondering why this happens as it is a show-stopper for me. Perhaps my transcode profile is wrong?

  4. #4

    Default

    Off-topic - but does Wowza offer Premium support, that would enable to get on the phone with your team to show you the problem first hand?

  5. #5

    Default

    This is hard to troubleshoot as I do not have a clear picture of what is happening.

    It sounds like there is an issue with sending VoD content through the Transcoder. I suggest trying this guide to convert the VoD content to a live source, and seeing if that helps:
    How to do basic server-side publishing with Stream class streams

    If it does not help, please open a support ticket by sending an email to support@wowza.com. Please include a reference to this post and a copy of the following files (as a .zip):

    [install-dir]/conf
    [install-dir]/logs
    [install-dir]/transcoder
    [install-dir]/manager/logs

    Wowza support is top notch (premium), but no they do not offer phone support.

    Salvadore

  6. #6

    Default

    Ok. I've narrowed it down to switched live streams using the Stream Class (VOD resides on the server, live stream from external encoder). When I use the Stream Class to switch to a VOD, and then use the HTTPLiveStreamRecord method to record the stream on the server, it works great. However, if I then use the Stream Class to switch to another VOD file on the server but the video dimensions to not match the dimensions of the first VOD file, it is not recorded properly. I'll send an e-mail to support with logs. Thanks.

  7. #7
    Join Date
    Dec 2007
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    21,962

    Default

    I can see where that might be problematic. I'm not sure what you can do about that. You might playback the stream in Flash debugger (like Flash builder) to look at metadata events, which are typically only sent and evaluated once in a most players. They are not built to expect a change in frame size and other metadata. But you might see multiple metadata events in such a recording. I can give that quick test...

    Richard

  8. #8
    Join Date
    Dec 2007
    Posts
    21,962

    Default

    This is actually not going to be supported in any case using Wowza because of the way files are written and metadata in a live stream. I'm not sure if it would work even if every file was encoded identically.

    You might try concatenating with another tool like FFmpeg. Or you can use a vod server-side playlist. However that only works in RTMP clients, and depending again on video and audio codec changes might still be a problem in playback clients when switching.

    Richard

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