On Mon, 6 Dec 2010 22:49:48 +0100
Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> On Monday, December 06, 2010 22:18:47 Antonio Ospite wrote:
[...]
> > Now the hard part begins, here's a loose TODO-list:
> > - Discuss the "fragmentation problem":
> > * the webcam kernel driver and the libusb backend of libfreenect
> > are not going to conflict each other in practice, but code
> > duplication could be avoided to some degree; we could start
> > listing the advantages and disadvantages of a v4l2 backend
> > opposed to a libusb backend for video data in libfreenct (don't
> > think in terms of userspace/kernelspace for now).
> > * Would exposing the accelerometer as an input device make sense
> > too?
>
> How do other accelerometer drivers do this?
>
input device of course, the question was more with regard to libfreenect
than linux...
> > The only reason for that is to use the data in already
> > existing applications. And what about led and motor?
>
> We are talking about LED(s?) on the webcam and the motor controlling the webcam?
> That is typically also handled via v4l2, usually by the control API.
>
I have to check whether the control API fits this case, the led (only
one) and motor are on another USB device: the Kinect sensor appears as
a hub with several distinct devices (camera, motor/led/accel, audio)
plugged in it.
[...]
> > - Decide if we want two separate video nodes, or a
> > combined RGB-D data stream coming from a single video device node.
> > (I haven't even looked at the synchronization logic yet).
>
> My gut feeling is that a combined RGB-D stream is only feasible if the two
> streams as received from the hardware are completely in sync. If they are in
> sync, then it would probably simplify the driver logic to output a combined
> planar RGB+D format (one plane of RGB and one of D). Otherwise two nodes are
> probably better.
>
Agreed.
> > - If a combined format would be chosen, settle on a format usable also
> > by future RGB-D devices.
>
> In general the video format should match what the hardware supplies. Any
> format conversions should take place in libv4lconvert. Format conversions do
> not belong in kernel space, that's much better done in userspace.
>
Ok, so if I wanted to visualize the depth data in a general v4l2 app,
then libv4lconvert should provide some conversion routines to some
2d image format like the "rgb heat map" in libfreenect; then the
question here becomes:
Is it OK to have depth data, which strictly speaking is not video
data, coming out from a video device node?
Are there any other examples of such "abuses" in kernel drivers right
now?
> Hope this helps. Sounds like this is a cool device :-)
>
Yeah, I played a little bit with accelerometers and image stabilization
(a primordial version of it), and it is fun:
http://blip.tv/file/get/Ao2-KinectImageStabilization247.webm
Regards,
Antonio
--
Antonio Ospite
http://ao2.it
PGP public key ID: 0x4553B001
A: Because it messes up the order in which people normally read text.
See http://en.wikipedia.org/wiki/Posting_style
Q: Why is top-posting such a bad thing?
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