Video lag and mirror image feature request
  • I've recently acquired a Logitech Brio 4K webcam for creating product demos. As many have commented online, the bundled software supplied by Logitech is minimalist, to say the least, and only allows simple screen viewing and changing of camera settings. No recording is possible. This is a bit odd because I bought a webcam from Logitech maybe a decade ago that came with software that had this simple functionality. But in any case, Logitech recommends Swiftcapture on their website, so I'm giving the trial version a go.

    I have two issues:

    1) Video lag on the Swiftcapture display panel is just over 2 seconds, which is much too high to be able to record a demo. Neither the Logitech software or Skype has this issue.
    2) I need to be able to mirror the video, otherwise, it's just too confusing trying to monitor what I'm doing on-screen.

    Hardware-wise I'm using a Mac Pro (Late 2013) trash can, 12GB RAM, AMD FirePro D300 2 GB video cards.

    Thanks in advance for any help.
  • I'm not sure why the lag is so high, though SwiftCapture is optimised for reliability and quality, not low latency of live video, which may explain the difference with Skype, which is of course optimised primarily for low latency. I expect also that Skype will be using a lower resolution and/or lower frame rate stream.

    Do you need the full 4K resolution for your recordings? If not, then you should specify a lower resolution in SwiftCapture's Preferences (e.g. 1920x1080 or 1280x720), as this should reduce the delay.

    As for a mirror function, SwiftCapture does not currently have this, however I think it's a good idea, so I will add this to the "to do" list for the next update.
  • Further to my previous message, we have now added flipping, rotation and mirror features to the latest beta version of SwiftCapture (currently 1.0.4b2).

    There are two new options in the Preferences:

    - Transformation: this provides various flipping and rotation options for the video stream. This affects both live and video.

    - Live video horizontal flip: this is the "mirror" mode that you describe above, whereby the live video is presented with a horizontal flip, as though you are looking into a mirror. This does not affect video capture; it just affects the live view.

    Please test this new version and confirm it works as expected.
  • Wow, that was quick on the feature request. Thanks!

    Apologies, I missed resolution details from my post. The resolution I'm using is 1080p @30fps. 4K is overkill for my needs. I had to reboot for another issue and have since tried it again.

    Lag is now aprrox 0.4 seconds, not perfect but pretty acceptable. Interestingly I tried the camera at 4K 30fps and I would say lag is 0.6 seconds.
  • Happy to help.

    A 0.4s latency for the live video at 1080p resolution sounds OK to me - I don't think it will be possible to improve on this. I have tested here with a few 1080p USB cameras and I'm seeing 0.5-1s latency. SwiftCapture processes the video frames as soon as they come in, though there is a certain amount of processing that has to be done between capture and display to the screen.
  • Looks like most programs dealing with video provide a live monitor window at a lower resolution in addition to the recorded/streamed full-res content to get around the latency issue. Just a thought...
  • The latency doesn't come from the live display to the screen - that bit is very fast and wouldn't benefit from a lower-resolution stream. The latency comes from the low-level work the driver has to do to obtain the stream from the camera, process it, and present it to the calling software. By the time SwiftCapture first sees the frame, some time has already passed since it was captured, and there is no way around this. I hope 0.4s is good enough for your purposes - it sounds quite low to me.
  • I've found some time to continue with my evaluation of SwiftCapture. The reboot, it seems, was a red herring. The long 2-second lag is still there, but I hadn't realised that it only materialises when recording. The 2-second delay is with 1080p@30fps.
  • If the lag consistently increases when recording, it's probably the extra processing load on the Mac's CPU that is causing the increased lag. I will see if there is anything in SwiftCapture that we can do about this, but it's possible that this lag is unavoidable while recording.

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