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[linux-dvb] V4L issues with linux dvb driver



  Hi, I am the author of tvtime, a realtime deinterlacer application for
V4L sources.  I've had a bug report [1] about our latest release failing
with this driver, and also, a report about poor performance.  This lead
me to investigate the linuxtv-dvb-1.0.0-pre1 source.

  The source notes that SAA7146 chips below revision 3 do not support
YUY2 images:

    /* all saa7146īs below chip-revision 3 are not capable of doing
     * byte-swaps with video-dma1. for rgb-grabbing this does not
     * matter, but yuv422-grabbing has the wrong byte-order, so we have
     * to swap in software */

  1. Please do not do format conversion in software.  I can easily
support UYVY in my application, and I need to do this for the rivatv
cards (which also currently converts in software, leading to more bug
reports about poor performance).  VIDIOCMCAPTURE  should fail on these
boards when asking for YUY2 images (VIDEO_PALETTE_YUV422).

  2. The VIDIOCSPICT ioctl currently always fails when asking for YUY2
images.  By the comment above, this should only happen with chips below
revision 3.  To support other drivers, my code must call this ioctl
before starting capture, so it would be nice to make this ioctl return
accurate information.

  3. By the code, the VIDIOCMCAPTURE ioctl will fail if you ask for
frames in UYVY format, which will make my support of it useless.  :)

  Thanks for your time,
  -Billy

[1] One of the bug reports is here, another complains about performance:
https://sourceforge.net/tracker/index.php?func=detail&aid=694544&group_id=64301&atid=506987

-- 
Billy Biggs
vektor@dumbterm.net


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