On Sat, Apr 11, 2009 at 2:39 AM, Theodore Kilgore
<kilgota@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> On Fri, 10 Apr 2009, Dongsoo, Nathaniel Kim wrote:
>
>> Hello everyone,
>>
>> I'm posting this RFC one more time because it seems to everyone has
>> been forgot this, and I'll be appreciated if any of you who is reading
>> this mailing list give me comment.
>
> I don't know much about the topic, and I wish I did.
>
>> I've got a big question popping up handling white balance with
>> V4L2_CID_WHITE_BALANCE_TEMPERATURE CID.
>>
>> Because in digital camera we generally control over user interface
>> with pre-defined white balance name. I mean, user controls white
>> balance with presets not with kelvin number.
>> I'm very certain that TEMPERATURE CID is needed in many of video
>> capture devices, but also 100% sure that white balance preset control
>> is also necessary for digital cameras.
>> How can we control white balance through preset name with existing V4L2
>> API?
>
> Let's broaden the question to include digital still cameras, which present
> similar problems. They present data related to this kind of thing, that is
> obvious. But are there any standard meanings to what is there? Do you know
> anything about that? Can you help?
>
Exactly right, but we need to see this on the top of the user space first.
Because there could be several types of camera devices could be handled.
I mean, the device that I'm intending to handle is based on I2C device
and the "digital still camera" you issued is totally based on USB
communication.
That could be different in driver implementation point of view, but
user in user space should be using in same manner.
And I think I can help to coordinate how to handle them in user space
with V4L2 API, but not so much with usb communication with digital
still cameras.(but I really want to help indeed)
Actually my expertise is totally based on mobile camera devices like
camera phone. Even though they are "mobile" camera modules, they are
very close to regular digital camera in performance and quality level
now days.
> Two examples:
>
> The SQ905 and SQ905C cameras in stillcam mode use an allocation table, which
> presents on each line some data about the given image. In this line, byte 0
> is a one-byte code for pixel dimensions and compression setting. Then some
> more bytes give the starting and ending locations of the photo in the
> camera's memory (actually irrelevant and superfluous information, because
> you can only ask for the photos in sequence, and with a command which has
> nothing to do with its memory location at all). Then some more bytes
> obviously have something to do with contrast, brightness, white balance,
> color balance, and so on. But I have no more idea than the Man in the Moon
> how those bytes are supposed to be interpreted. The SQ905 gives no such
> equivalent information while in streaming mode, and so there is nothing at
> all which could be done with the nonexistent information. But the SQ905C
> does obviously give such information, in a few bytes in the header of each
> frame.
As far as I know, SQ905 (is that actually cheez camera?) is a regular
digital camera not a mobile camera module, so in that case it could be
handled in gspca and totally control through usb_control_msg.
And with my experience, I think I can help you if I have any kind of
datasheet or user manual for that.
But even if I don't have datasheet and don't know which message field
means what I'm intending to do, I think it could be possible to make
it compatible with the parameters I'm trying to make in v4l2 control.
>
> The MR97310A cameras give similar information in the header of the photo
> itself (and in this case the camera does the same thing in webcam mode,
> too). Again, I have no idea either what these mysterious bytes are supposed
> to mean, and how to use them constructively.
>
> I could mention several other examples, too, but these will do for a start.
OK I've got what you mean. Can I have any information like user manual
or datasheet for those SQ and MR devices?
If we make a white balance preset api in v4l2, then we should have to
implement that functionality in every single camera drivers in v4l2 if
those devices are supporting for white balance presets.
I want to make this clear that if we have white balance preset api in
v4l2, then we can handle every camera device's white balance more user
friendly.
Thank you for your opinion by the way.
Nate
>
> Are there any agreed-upon standards about this kind of thing, in the camera
> industry? Is there any source of information about it?
>
> Theodore Kilgore
>
--
========================================================
DongSoo, Nathaniel Kim
Engineer
Mobile S/W Platform Lab.
Digital Media & Communications R&D Centre
Samsung Electronics CO., LTD.
e-mail : dongsoo.kim@xxxxxxxxx
dongsoo45.kim@xxxxxxxxxxx
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