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Thread: NDI Scan Convertor v3.7 - ignoring webcam settings

  1. #1
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    NDI Scan Convertor v3.7 - ignoring webcam settings

    Hi All,

    I just updated two PCs to NTI Tools v3.7. Wanted to see if the lesser of two could be used to access a Logitech C922 webcam, making it available as an NDI source.

    When I do this, the NDI stream offered is 640x480p30 4:3 aspect ratio. This happens almost completely without regard for the settings selected in NDI convertor.

    It only switches to 16:9 aspect if some very low resolution setting is selected, like 640x360.

  2. #2
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    Quote Originally Posted by mjgraves View Post
    Hi All,

    I just updated two PCs to NTI Tools v3.7. Wanted to see if the lesser of two could be used to access a Logitech C922 webcam, making it available as an NDI source.

    When I do this, the NDI stream offered is 640x480p30 4:3 aspect ratio. This happens almost completely without regard for the settings selected in NDI convertor.

    It only switches to 16:9 aspect if some very low resolution setting is selected, like 640x360.
    Tracking this a little further, it appears that any time Scan Convertor is unhappy it's failure mode is to select 640x480p30 4:3.

    It cannot access a Logitech Brio or Rally at 4k30. It always resorts to a VGA default.

    FWIW, you should take note from lessons learned elsewhere, when accessing Logitech 4K capable webcams you should use the MMF access method. Direct Show does not work well.

  3. #3
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    Same issue with 3.5 for the 3 cams?

  4. #4
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    Hey did you ever have any luck with fixing this? Having the same issue with my Logitech c930e.

  5. #5
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    Revisiting this old issue in the light of NDI Tools v3.8.

    Scan Converter offers, but does not support, 4K or DCI resolutions from USB 3 connected sources. For example, connecting to a Logitech Brio 4K webcam it returns 640x480p30 (4:3), which is simply the default used when it fails to configure the device.

    The same is also true for a Logitech Rally 4k PTZ camera.

    We infer that Scan Convertor has no intelligence about the requirement for different compression modes or sampling schemes associated with different devices.

    To achieve 1080p30 with a USB 2 device requires the MJPEG or H264 modes supported in UVC 1.5 (circa 2012)

    Similarly, to achieve 4k30 with a USB 3 device requires the use of MJPEG or NV12 encoding.

    We know that vMix has implemented access to Brio using MMF (not Direct Show) with NV12 encoding. This reliably delivers 4k30 with minimal latency. MS Camera also uses MMF to access these devices at 4K.

    These realities are not confined to USB-attached cameras. They apply to USB attached capture dongles as well. These are becoming commonplace from the likes of Yuan, Magewell, etc. Most especially as people try to do more with laptops.

    I suggest that it's time to extend NDI Scan Convertor to deliver what the menu offers. Or eliminate the offer from the menus.

  6. #6
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    I've opened a support ticket about the manner in which "Scan Convertor" and "Connect" handle webcams. It's basically faulty. I've tested with a number of Logitech webcams from the old C920 to the Rally 4K PTZ camera, providing notes about how the software fails to deal with each in various ways.

    https://fogbugz.newtek.com/default.asp?100426
    Last edited by mjgraves; 06-12-2019 at 10:13 AM.

  7. #7
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    For those that might need it I'll explain my work around to this issue (It is not a "fix" to the problem with Scan Converter).
    Use OBS Studio and add your webcam as a Video Capture Device, set the resolution you want and output that with the OBS plugin "OBS-NDI" through Scan Converter as a regular Desktop instead of a Webcam.

    Basically you just circumvent/replace NDIs poor USB Webcam support with OBS far superior one.
    Hopefully this helps someone until NDI updates their software.

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