Comment 0 for bug 542042

Regression: skype webcam (Chicony CNF7129) image very dark on Asus 1000HE on Karmic (9.10) UNR,
works on Jaunty (9.04) UNR

Summary:

Skype has regressed in Karmic UNR on Asus 1000HE - CNF7129 camera image extremely dark.
Webcam image works in Jaunty UNR on Asus 1000HE (and Asus 901 as well - same camera).
Specific to skype; cheese works fine on both Jaunty and Karmic. Initial image
is just a little dark on startup, then darkens to almost black after a fraction
of a second.

Hardware: Asus EEE 1000HE / Chicony CNF7129 webcam (builtin)
Skype: skype-ubuntu-intrepid_2.1.0.81-1_i386.deb (current) from
    http://www.skype.com/download/skype/linux/choose/ (Ubuntu 8.10+ 32 bit)
    (The same .deb was tested on Jaunty UNR (works) and Karmic UNR (fails))

Some related packages:
    Jaunty UNR (tested using liveusb and/or installation):
        kernel from distro(liveusb)
        libv4l-0 from distro(liveusb) or 0.5.8-1

        lsmod | fgrep vid
        uvcvideo 63368 0
        compat_ioctl32 9344 1 uvcvideo
        videodev 41600 1 uvcvideo
        v4l1_compat 21764 2 uvcvideo,videodev
        video 25872 0
        output 11008 1 video

     Karmic:
        kernel 2.6.31-20-generic
        libv4l-0 0.6.0-1

        lsmod | fgrep vid
        uvcvideo 59080 0
        videodev 36736 1 uvcvideo
        v4l1_compat 14336 2 uvcvideo,videodev
        video 19380 0
        output 2780 1 video

Other scenarios tested:

- Tried skype_2.0.0.72.orig.tar.gz on Karmic UNR. Webcam image is just as bad/dark.
  This version of skype also works on the Asus 901 / Jaunty (same camera).
  Not surprising, given that the latest skype .deb works on Jaunty but gives
  dark images on Karmic. (Both skype's work on Jaunty; latest fails on Karmic.)

- Tried 'LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so skype'. No effect.

- Tried the latest libv4l-0 from https://launchpad.net/~libv4l/+archive/ppa
  No improvement. According to the page, this includes what's below, but no improvement.

      Package Version Uploaded by
      gtk-v4l 0.1-1 Stephane Marguet (2010-02-25)
      libv4l 0.6.4-1+hg20100220~kkv4l2 Stephane Marguet (2010-03-10)
      v4l-utils 0.7.91-1~kkv4l1 Stephane Marguet (2010-03-12)
      v4l2ucp 2.0.2-1~kkv4l1 Stephane Marguet (2010-01-29)

- Tried luvcview. Adjustments to brightness and/or gamma are not sufficient
  to get an image as bright/balanced as cheese. Changes have an effect,
  but they are minimal, still too dark to be acceptable, and not nearly
  as good as cheese

- Tried xawtv/v4lctl. Effects are the same as luvcview, and still too dark and
  not nearly as good as cheese

- Tried guvcview. Same as luvcview and v4lctl / not enough effect.

- None of the V4L tools above provide access to an auto exposure or auto gain
  setting. Interesting, since the "initially some brighter, fade to almost black"
  effect on startup really seems like an "exposure" adjustment taking place, and
  an auto exposure exposure seems to be in effect for cheese.

These are my current conjectures:

- Problem is not the skype deliverable (.deb). Same .deb file, same hardware.
  Jaunty works, Karmic fails. Not the CNF7129 either, since cheese works on both
  Jaunty and Karmic.

- I've read that Jaunty may be V4L1, Karmic V4L2, skype build uses V4L1.
  If correct, could be a V4L1/2 compatibility problem. Might even be an
  auto exposure or auto gain that is missing from or bad in the compatibility API.
  None of the *uvcview tools show exposure/gain as being settable. The skype
  startup behavior "looks like" a fairly quick exposure compensation on webcam startup.
  As a photographer, this looks *so* much like an auto exposure control missing.
  This could also explain why cheese works and skype fails.

- Could be in the video module/driver (uvcvideo). I don't know how Jaunty differs
  from Karmic in its webcam drivers. (How can this explain cheese working and
  skype failing?)

- Cheese images are somewhat brighter than skype images, even on Jaunty UNR. Not terribly
  different, but brighter. Maybe for Karmic, cheese images were "adjusted down",
  which would make skype images even darker. Again as a photographer, I don't
  think this is the explanation -- the skype images are *much* darker, almost black --
  and much darker than explained by just darkening the cheese images a little bit.
  But I cannot rule this out entirely.