[PD] Using ov519 webcams (Eyetoy) with pdp/Gem (jpeg frames)

Mathieu Bouchard matju at sympatico.ca
Sun Dec 19 18:23:13 CET 2004

On Sun, 19 Dec 2004, Georg Holzmann wrote:

> I also just bought an ov518 camera (Terratec TerraCam USB) and use the
> ov51x driver with JPEG compression.
> (I think it has the compression, at least in the driver README stands:
> For OV518/OV518+ cameras: Compression support is built into ov511.o and
>    enabled by default.
> )

I heard about a decision from the linux-kernel guys that image format
conversion code should not be in kernel drivers anymore. Unfortunately
this puts all the burden of conversion on the application. To make things
worse, there are no user-mode provisions in the V4L1 interface, so _if_
there was any user-mode wrapper that would make a V4L1 driver available in
all color-models and such, programs would have to be recompiled using a
function that may behave like ioctl() but can't be named ioctl(). (am I
being clear?)

Now, I don't know the specifics of the ov518 camera and/or driver and
whether or not it has the capability to give uncompressed frames.

I figured out that if you want to know which colormodels are supported in
a given V4L1 driver you have to send a request for each possible color
model and figure out whether it was accepted or not.

Actually now that I look at it, those things are called "palettes" in the
V4L1 interface. GridFlow reports this when you open the camera:

[gf] This card supports palettes: 0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 13, 14,
15, 16

Those numbers are the palette #define's of /usr/include/linux/videodev.h.

Mathieu Bouchard -=- Montréal QC Canada -=- http://artengine.ca/matju

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