How to deal with video mixer lag in live mix

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    • #39729
      Avatargshantz
      Participant

      I am using 2 remote Sony cameras fed into an Edirol V4 mixer and supplying the video mix and house sound separately to a recorder. The video feed is also being used live in a place where people can see both live and feed together. Theoretically, everything should be synced and live – actual visual, video image, and audio. In reality, I’m getting a slight delay going through the mixer – enough for some viewers to question :-//, but barely enough to measure or be certain of. The only way I could quantify it was to clap in front of a camera or watch a guitar string being plucked. There is the obvious time delay in the audio if standing or sitting far enough from the source of sound, but this tends to help out for live viewing. I’m more concerned about what goes to disc for premanent record.

      Is there any remedy for this situation? I’ve queried and looked for a long time here and elsewhere for a similar subject to no avail.

      Another issue I have is (RF) interference coming down the video cable. I say RF because it is the only thing I can think of. We are using RG 6 coax cable with RCA connectors on each end. I’ve tried to keep all connectors really clean and tight. There are times when it goes away, but usually not for very long and I can’t relate it to anything. I’m guesing that the cable length is between 50 and 100 ft. The result of the interference is a 45 degree diagonal pattern across the screen. :'(

      Thanks for any suggestions

  • #171443
    Avatarralck
    Participant

    I’m not sure about the sync problem, but I’ll try and help on the RF problem.

    My main thought with this is, if you are going to be running cable 50 to 100 feet (well, anything over about 10-15 feet) you should be using balanced cables. These will help eliminate any interferrence. The other thing is, if you have to cross your cable with any power wires or power cables, try and cross them at a 90 degree angle. This will help eliminate any cross talk.

  • #171444
    BrianBrian
    Participant

    Ive run 150 foot long composite video cables with the Edirol without any problems. For best results use heavy-duty broadcast composite cable, not Y/C cables. Y/C cables have a tendency to create Chroma shift due to the color portion of the signal and the luminance portion arriving at two different times, this is called Y/C Delay.

    Also look into a sync generator.

  • #171445
    AvatarAnonymous
    Inactive

    The delay (probably a frame or two?) is most likely caused because your cameras are not sync’d to your switcher which has its own built in synchronization circuits which will delay the signals. If you can, genlock your cameras on the same length cable to the same black burst generator. (If not, but you do have at least one genlockable camera, genlock it to the video signal from the other camera)

  • #171446
    Avatargshantz
    Participant

    tonsofpcs Wrote:

    The delay (probably a frame or two?) is most likely caused because your cameras are not sync’d to your switcher which has its own built in synchronization circuits which will delay the signals. If you can, genlock your cameras on the same length cable to the same black burst generator. (If not, but you do have at least one genlockable camera, genlock it to the video signal from the other camera)

    Thanks Eric, I’ll have to do some research as to if and how to genlock these cameras. They are a pair of Sony EVI-D70. My tech guruh is on a week and a half vacation, so need to wait for him to return.

    I’m wondering if the delay is a normal thing in the mixer, how does one handle the audio which now goes direct to the recording device? Is that left to the higher end professional mixing consoles that can sync the audio with the video? The Edirol doesn’t have any means to do this. Maybe we shouldn’t be so picky on a budget system. 😮

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