Streaming raw video over USB

Technical Support
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1

Hello all,

I am trying to capture RAW PAL video input and stream it over USB.
It’s sort of an intelligent USB camera project.

Capturing PAL video works without problems.
I was wondering if you can guide me regarding streaming raw video over USB.

If possible it would be great to act as a camera that supports usb video class.
My platform is apalis imx6 and ixora

Best Regards
Rifo

2

Hi @rifo !

Could you please share the output (as text) of tdx-info on your module (Getting Device Information with Tdx-Info | Toradex Developer Center)?

Could you please share a block diagram of what you are trying to accomplish? It will help us to understand your use case.

Best regards,

3

Hello,

You can find the block diagram above.

Ixora gets raw data from PAL camera. This works fine.

I plan to stream this “raw” video data from Ixora to USB with gst-launch. I would be happy if you can guide me regarding this.

block_diagram
block_diagram802×553 21.8 KB

ps: I will post tdx-info output later on when I have access to the hardware again.

Best Regards
rifo

4

Hi rifo

To act as UVC camera, you need UVC USB gadget. If you have functioning /dev/video? of your capture device, then it should be quite easy to feed it to UVC gadget device. Hope this thread will help
Solved: UVC webcam gadget on i.MX8 HW - NXP Community

Edward

5

Thanks a lot.

I understand that UVC webcam gadget sends mjpeg encoded video stream.

I will check whether I can use mjpeg encoding in a lossless way.

Rifo

6

Unfortunately I did only bare metal UVC camera project in the past and didn’t try myself the same on Linux. UVC supports not only compressed stream- and frame based payloads, but as well uncompressed frame based payload (either packed 4:2:2 YUV format (YUY2) or 4:2:0 YUV format (NV12)).
uvc-gadget -f switch:

-f <format>    Select frame format
            0 = V4L2_PIX_FMT_YUYV
            1 = V4L2_PIX_FMT_MJPEG

Googling reveals that “V4L2_PIX_FMT_YUYV is known in the Windows environment as YUY2”. So this seems to be what you need for uncompressed video.

7

Thanks a lot Edward,

I think this will be fine with my case

Best Regards
rifo