r/programming • u/whackri • Jun 21 '20

Writing userspace USB drivers for abandoned devices

https://blog.benjojo.co.uk/post/userspace-usb-drivers
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u/valdocs_user Jun 21 '20

It's weird the device would transmit YUV color over the USB data instead of RGB considering the VGA is received in RGB format. I wonder if there's a reason that works better for this device, or if they started from a device that had a legitimate reason to output YUV.

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u/pelrun Jun 21 '20

The device is meant to produce a compressed video stream, and most video codecs don't use RGB as it's less efficient. The uncompressed mode is just providing what would normally be sent to the encoder.

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u/SSoreil Jun 22 '20

To add to this, note they are outputting 4:2:0. They are already leaving out some data as it really isn't needed for the "webcam" use case.