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Thread: Logitech Brio 4k transmitted with 640x480

  1. #16
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    Does your vMix license support 4K? Only the 4K or Pro licenses do. Martin, CEO of vMix, tells us that NV12 is currently supported. I've verified that at 1080p but I cannot do so at 4K.

  2. #17
    Quote Originally Posted by AlanZ View Post
    Thanks, now does anyone think that NDI can also enable the format?
    NDI can handle 4K and beyond and is independent of the compression formats webcams work in. What matters here is finding an application interface that supports the webcam at the resolutions desired.
    Kane Peterson
    Key Accounts Sales Engineer
    NewTek, Inc.

  3. #18
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    Kane,

    I am a bit confused. If I use scanconverter to ingest a Brio at 4k, and bring it into vMix as an NDI source (not as a camera input), it comes in at 640x480. So does that suggest that NDI is not seeing the camera at full resolution?

  4. #19
    NDI sends what the application makes available.

    I think I see possible what you are talking about though. Looks like it can be webcam specific.

    My laptop's built in webcam, doesn't deliver higher than 640x480 either, even though higher resolutions are available to select. In OBS I get all of the resolutions correctly.

    My Logitech C920 webcam works correctly, I can get all the way up to 1080p with it.

    I'll bug it. My guess is that some webcam compression modes are supported and some aren't.
    Kane Peterson
    Key Accounts Sales Engineer
    NewTek, Inc.

  5. #20
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    With webcams there are various modes of operation. They might deliver VGA resolution using RGB24, YUY2 or I420. These are really different sampling schemes for uncompressed output. Curiously, quite often the sampling scheme is tied to the frame resolution.

    The USB link limits how much data can be passed to the host. So [email protected] is the limit for uncompressed YUY2 over USB2.

    Manufacturers responded by creating webcams that had on-board MJPEG or H264 compression. This allows 1920x1080p30 over USB2.

    MJPEG normally does not increase latency since each frame is compressed individually. H246 always introduces latency because it requires an entire group of frames (30-120) to be processed before the stream leaves the camera.

    Since Brio has a USB 3 connection to the host it can deliver 1080p30 YUY2. It can actually deliver 1080p60 YUY2!

    4k30 YUY2 simply will not fit across USB3. To deliver 4k30 the host application must set the camera to deliver an MJPEG compressed stream.

    For some reason, when set for 1080p30 the MJPEG delivered is not delayed. When set for 4k30 there are several frames of additional delay. At least, that's what we see with most apps, including; Scan Convertor, vMix and OBS.

    Curiously, the MS Camera app manages to extract 4k30 from Brio without that latency. I'm told that this is because it doesn't use Direct Show. It uses Microsoft Media Foundation (MMF) which is much newer. It's unclear how these things differ exactly. There are very few MMF apps in existence today.
    Last edited by mjgraves; 06-27-2018 at 12:01 PM.

  6. #21
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    I just tried scan convertor myself for the first time. There's just a simply error in how it handles the Brio camera. It doesn't seem to specify encoding type when selecting 4K, which results in a default back to VGA 4:3. This should be easily fixed.

    My prior post, while a good background, doesn't really apply here. This seems like a simple issue.
    Last edited by mjgraves; 06-29-2018 at 08:44 AM.

  7. #22
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    I am having the same kind of issue with my logitech c930e, where when I choose any resolution, it defaults to 640x480 4:3. Any fix for this?

  8. #23
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    Note that some time after this thread was underway, vMix implemented MMF access to Brio. That uses NV12 encoding (4:2:0 8 but) supporting reliable 4k30 operation without latency.

    You can't get decent 4K30 from Brio using Direct Show. It requires MMF.

    Elsewhere hereabouts I've updated a thread noting the problems with Scan Converter in this regard. It still cannot cope with any USB video source that requires the use of compressed modes to get the stream across the USB link.

    That limits USB 2 webcams to 720p30 and USB 3 webcams to 1080p30. Even though the cameras can deliver better resolutions and frame rates.

  9. #24
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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.

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