[libavg-devel] video4Linux2 on libavg: some design choices

[Ben Lau]

On 6/25/07, OXullo Intersecans <x at 02l.net> wrote:
>
> Il giorno 25/giu/07, alle ore 17:21, Ulrich von Zadow ha scritto:
>
> > Hi,
>
> dearest,
> that's good to hear you again!
>
> > looks like everything is coming along very well :-).
>
> yep! the port is almost done, we should test it.
> Ben, have you got some feedback for us?

May I know what is your capture device in hand? I saw the code
supports YUV422, but unfortunately none of my USB capture devices
support this pixel format. I have a Logitech Quickcam Pro 4000 (PWC) ,
Logitech Quickcam for Notebook Pro (UVC) , Pinnacle Dazzle DVC
90(em28xx) and Kworld DVD maker(em28xx). They use YUV420P or YUYV as
input format.

I have tried to fix the problem, but the Bitmap class do not support
the conversion from YUV420P to YUYV. I think it could be done by
follow the template of YUV422toBGR32Line() and YUV411toBGR32Line() to
write a YUV420toBGR32Line() , then fill up the Bitmap::YCbCrtoBGR().

( Attached my work to recognize YUV420 for avg layout file , and
prompt error message when the assigned image format is not support)

>
> > Do you think you can check a version that works and doesn't break
> > anything old into subversion before the weekend? Then I'll try it
> > here,
> > maybe fix firewire if that's necessary and see if I can commit the
> > stuff
> > that you've done to trunk.
>
> We worked mostly in a independent way, Camera code *should* work, but
> we have no such IDC camera to make testing.
> Unit tests work flawlessy, the only relevant bug was pointed out by
> Ben Lau and a workaround has been applied, waiting to a better
> solution (see below).
> Our latest commit is someway in line with the latest additions
> (merged till rev2131)
>
>
> >> mode: WxH_PF where PF can be: RGB, MONO8, YUV422 (the same as
> >> firewire
> >> camera)
> >> channel: video mux selector, for example, a bt878 pci board has:
> >> 0=tuner, 1=composite, 2=svideo
> >> source: 'v4l' instead of 'firewire' is the magic switch
> >
> > Looks good. The 'mode' attribute seems a bit strange to me in the v2l
> > case, but I don't have any good idea how to change it.
>
> sure? we followed your traces!
> <width>x<height>_<pixelformat>
>
> you'll see a tokenizer on V4LCamera.cpp code to split up these two
> fields. Furthermore another tokenization between width and size seems
> to be due
>
> >> We split this method in two: addFWTracker(device, mode) and
> >> addV4LTracker(device, mode, channel). This seems not to be the
> >> best way,
> >> but was the fastest, waiting for some Uli's advices basing on his
> >> best
> >> flavours.
> >
> > Yeah, that doesn't seem like we want it to stay that way. I'll look at
> > the code over the weekend.
>
> waiting for your suggestions!
>
> >> At this time, V4LCamera does not honour tune-in attributes, therefore
> >> the <camera> node of the rc is simply ignored.
> >
> > Are you going to implement that? If not, we should throw an error
> > if the
> > camera node is there.
>
> gone with the last two commits
> unsupported features (they may vary) are simply ignored with a WARNING
> you'll notice that if you instantiate a CameraNode you'll receive a
> non-fatal error of a setFeature() called before device initialization.
> Will we have to proxy feature set requests and throw them only at
> device initialization time?
>
> For now, features are set in real-time and with no further values
> storaging.
>
> byez!
>
> --
> OXullo Intersecans
>
> 0 2 L > Outside Standing Level
> http://www.02L.net
>
>
>
>
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