On Mon, 11 Apr 2011 23:07:36 +0200
Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
[...]
> > I don't know libv4l yet, so I am asking for advice providing some code to
> > discuss on; looking at the last hunk of the patch: can I allocate a temporary
> > buffer only once per device (and not per frame as I am horribly doing now) and
> > reuse it in the conversion routines?
>
> libv4l has a mechanism for doing this, you can "simply" do:
>
> unpacked_buffer = v4lconvert_alloc_buffer(width * height * sizeof(unsigned short),
> &data->convert_pixfmt_buf,
> &data->convert_pixfmt_buf_size);
>
> v4lconvert_alloc_buffer will remember the buffer (and its size) and return the
> same buffer each call. Freeing it on closing of the device is also taken care
> of. You should still check for a NULL return.
>
Thanks that works fine: I am still not sure I like passing
'v4l2convert_data' to the pixelformat conversion routines but we'll
discuss that on the next review round.
> What has me worried more, is how libv4l will decide between asking
> Y10B grey versus raw bayer from the device when an app is asking for say RGB24.
> libv4l normally does this automatically on a best match basis (together with
> preferring compressed formats over uncompressed for high resolutions). But this
> won't work in the kinect case. If we prioritize one over the other we will
> always end up giving the app the one we prioritize.
>
Mmh, I tried to materialize your worries, these are the native modes
supported:
- GRBG mode at 640x480 and 1280x1024
- UYVY mode ay 640x480
- Y10B mode at 640x488 and 1280x1024
^
and this is the behavior I am observing in qv4l2 when in _wrapped_ mode:
- If I choose the RGB3 output format all the three different
resolutions are selectable:
+ at 640x480 I get the color image, as there is no greyscale
format at the same resolution,
+ at 640x488 I get the grayscale image, as there is no color
format at the same resolution,
+ if I choose 1280x1024 I get the grayscale image indeed, and I
loose the possibility of using the color image.
Everything works fine in _raw_ mode of course where only the native
formats are shown.
Ah, a strange thing (to me at least) happens in _wrapped_ mode even for
GRBG (which is supposed to be a _native_ color format for the device):
I get the grayscale image at 1280x1024 instead of the color image; can
this just be a bug somewhere in qv4l2 or lib4vl?
> The only thing I can think of is adding a v4l2 control (like a brightness
> control) for choosing which format to prioritize...
>
and this control would be created by libv4l when in wrapped mode?
Thanks,
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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