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Thread: aTime and vTime out of sync IP camera

  1. #1
    Join Date
    Feb 2014
    Posts
    6

    Default aTime and vTime out of sync IP camera

    Hi. I have a Grandstream GXV-3651-FHD IP camera that gets its audio input from an output off of an EAW DX810 digital mixer about 150 ft. of cable away. The camera outputs an H.264 stream with ACC audio (although the manufacturer seems to prefer PCMU or PCMA). I am using Wowza 4.0 to grab the stream via rtsp directly from the camera. The server and camera are on the same local network (although on different V-LANs).

    When I had the nDVR add-on turned on for this stream, I saw errors like the following in the log:

    WARN server comment - DvrStreamStoreBase.storeChunks[StDominicChurch/_definst_/StDominic.stream/StDominic.stream.0] : Skipping chunk. A/V packet times differ by 745668 ms, more than allowed 2000 ms. aTime=13799624 vTime=13053956
    WARN server comment - DvrStreamStoreBase.storeChunks[StDominicChurch/_definst_/StDominic.stream/StDominic.stream.0] : Skipping chunk. A/V packet times differ by 745773 ms, more than allowed 2000 ms. aTime=13801733 vTime=13055960

    With the nDVR add-on active on this stream, it kept dropping out or having to re-buffer quite often on live viewing. When I disabled the nDVR add-on, the live stream looked fine - audio and video in sync with no drops or re-buffering. When I recorded the stream and watched the playback, the audio was about 7 seconds late, but otherwise, looked (and sounded) fine.

    The camera uses the Wowza server as an NTP time source.

    How can the aTime and vTime be so far off when the camera itself acts as the encoder? Is the digital mixer to blame? What can I try to fix this?

    Thanks.

  2. #2
    Join Date
    Dec 2007
    Posts
    22,013

    Default

    A/V sync issues in encoders are not uncommon. The two Wowza Properties that might have some affect are dvrAllowableAVPacketDelta and dvrPacketSortTime, which are explained in the DVR Advanced Guide

    Richard

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