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Aug 19, 2023 •794 likes •966 views

libv4l Hans de Goede Red Hat Contents Introduction Future (from last years presentation) Emulated controls When to enable? Video processing Future Introduction Fedora better webcam support feature:

  1. libv4l Hans de Goede Red Hat

  2. Contents ● Introduction ● Future (from last years presentation) ● Emulated controls ● When to enable? ● Video processing ● Future

  3. Introduction ● Fedora better webcam support feature: http://fedoraproject.org/wiki/Features/BetterWebcamSupport ● Get gspca into the mainline kernel ● Remove format conversion from gspca ● Applications don't handle the new formats ● Sollution: Write a conversion library ● And patch ALL applications to use it

  4. The Future? ● Add emulated controls ● Better handle rotation ● Software image quality enhancements: – White balance – Normalize ● Software image quality enhancements have a separate measure / transform phase ● GET_WEBCAM_ATTR ioctl ● Emulated controls persistency

  5. Emulated controls ● Persistent ● Shared ● Using shared memory: /dev/shm/libv4l-hans:usb-0000:00:1d.7-5: BisonCam NB Pro ● Disadvantage: settings are per user

  6. When to enable ? ● Enabling emulated controls, forces libv4l to go through the conversion path, even when not converting. ● libv4l has a device table for devices which benefit from software video processing. ● Also enabled when the device will always need conversion.

  7. Video Processing ● White balancing, simple make image gray on average algorithm ● Gamma correction ● Manipulate per component (RGB) component lookup tables, so once sort of processing is enabled, further processing is essentially free. ● Only works in RGB color space, requires YUV -> RGB -> YUV conversion in certain cases

  8. The Future ● Add plugable processing algorithms, so that we can have driver specific algorithms ● Move quirk table to a config file ? ● Support for software auto focus ? ● Support for video input device sharing ? ● Get more out of tree drivers into the mainline, port mainline v4l1 drivers to v4l2

  9. libv4l Hans de Goede Red Hat

  10. Contents ● Introduction ● Future (from last years presentation) ● Emulated controls ● When to enable? ● Video processing ● Future

  11. Introduction ● Fedora better webcam support feature: http://fedoraproject.org/wiki/Features/BetterWebcamSupport ● Get gspca into the mainline kernel ● Remove format conversion from gspca ● Applications don't handle the new formats ● Sollution: Write a conversion library ● And patch ALL applications to use it

  12. The Future? ● Add emulated controls ● Better handle rotation ● Software image quality enhancements: – White balance – Normalize ● Software image quality enhancements have a separate measure / transform phase ● GET_WEBCAM_ATTR ioctl ● Emulated controls persistency

  13. Emulated controls ● Persistent ● Shared ● Using shared memory: /dev/shm/libv4l-hans:usb-0000:00:1d.7-5: BisonCam NB Pro ● Disadvantage: settings are per user

  14. When to enable ? ● Enabling emulated controls, forces libv4l to go through the conversion path, even when not converting. ● libv4l has a device table for devices which benefit from software video processing. ● Also enabled when the device will always need conversion.

  15. Video Processing ● White balancing, simple make image gray on average algorithm ● Gamma correction ● Manipulate per component (RGB) component lookup tables, so once sort of processing is enabled, further processing is essentially free. ● Only works in RGB color space, requires YUV -> RGB -> YUV conversion in certain cases

  16. The Future ● Add plugable processing algorithms, so that we can have driver specific algorithms ● Move quirk table to a config file ? ● Support for software auto focus ? ● Support for video input device sharing ? ● Get more out of tree drivers into the mainline, port mainline v4l1 drivers to v4l2

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