v4l2_pix_format doubts

v4l2_pix_format doubts

[Veda N]

I am trying to fill the structure v4l2_pix_format in the camera driver.

The v4l2_pix_format has the following variables to fill
  a) bytesperline
  b) width
  c) height
  4) pixelformat

 My datasheet says the size of each pixel is 12 bits per color channel.

 Hence for RGB will be 36bits.

 I wanted to know if the same hold true for YUV data.

In that case i was confused how to fill the bytesperline, width and
height field.

Can anyone help on this?

For 640x480 pixels what should be the value i should fill.

I am confused because for most drivers they take as 2 bytes per pixel.


Where are in my case i think it would be 36bits per pixel. am i wrong?



Regards,
vedan

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Re: v4l2_pix_format doubts

[Daniel Glöckner]

On Tue, Jun 17, 2008 at 02:35:04PM +0530, Veda N wrote:
>  My datasheet says the size of each pixel is 12 bits per color channel.
> 
>  Hence for RGB will be 36bits.
> 
>  I wanted to know if the same hold true for YUV data.

Can you tell us for which hardware you want to write a driver?

The values to fill in depend on the final layout of the data in memory.
As you should not convert to YUV in software, it depends solely on the
hardware.

  Daniel

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Re: v4l2_pix_format doubts

[Xuesong Yang]

在 2008-06-17二的 14:35 +0530，Veda N写道：

> The v4l2_pix_format has the following variables to fill
>   a) bytesperline
>   b) width
>   c) height
>   4) pixelformat

Just a guess
a  640x12x3/8
b 640
c 480
4 this should be one of the enum type

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Re: v4l2_pix_format doubts

[Veda N]

Hi Daniel,

  Thank you for your quick response.


On Tue, Jun 17, 2008 at 2:54 PM, Daniel Glöckner <daniel-gl@gmx.net> wrote:
> On Tue, Jun 17, 2008 at 02:35:04PM +0530, Veda N wrote:
>>  My datasheet says the size of each pixel is 12 bits per color channel.
>>
>>  Hence for RGB will be 36bits.
>>
>>  I wanted to know if the same hold true for YUV data.
>
> Can you tell us for which hardware you want to write a driver?
>
> The values to fill in depend on the final layout of the data in memory.
> As you should not convert to YUV in software, it depends solely on the
> hardware.


  As i understand, my camera has a image processor inside it. what i
want to say is it is
  not a plain raw sensor.

  For every pixel clock a pixel is fetched from the device and is
placed in memory
  Once a entire frame is captured. it is returned to the application.
>From the application
   i can write this data into LCD or a file to be viewed by a YUV/RGB
viewer like YUVTOOLS.

  This is same for both RGB and YUV data.


  my only concern is i should fill proper values to v4l2_pix_format structure.

  Thank you.

Regards,
vedan

>
>  Daniel
>

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Re: v4l2_pix_format doubts

[Daniel Glöckner]

On Tue, Jun 17, 2008 at 03:09:04PM +0530, Veda N wrote:
>   As i understand, my camera has a image processor inside it. what i
> want to say is it is
>   not a plain raw sensor.

So this image processor converts RGB to YUV?

>   For every pixel clock a pixel is fetched from the device and is
> placed in memory
>   Once a entire frame is captured. it is returned to the application.

And if you look at this data in memory, what does it look like?

  Daniel

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Re: v4l2_pix_format doubts

[Veda N]

I think you got confused by RGB and YUV.

The device is capable of giving RGB and YUV data. This is done by a
setting in the sensor register.

Once i set the value, For every pixel clock a pixel is fetched from
the device and is
placed in memory  Once a entire frame is captured. it is returned to
the application.
>From the application   i can write this data into LCD or a file to be
viewed by a YUV/RGB
viewer like YUVTOOLS.


Now, i know what i should set the pix->pixelformat, but what about
other members of the
v4l2_pix_format structure.



Regards,
vedan

On Tue, Jun 17, 2008 at 3:15 PM, Daniel Glöckner <daniel-gl@gmx.net> wrote:
> On Tue, Jun 17, 2008 at 03:09:04PM +0530, Veda N wrote:
>>   As i understand, my camera has a image processor inside it. what i
>> want to say is it is
>>   not a plain raw sensor.
>
> So this image processor converts RGB to YUV?
>
>>   For every pixel clock a pixel is fetched from the device and is
>> placed in memory
>>   Once a entire frame is captured. it is returned to the application.
>
> And if you look at this data in memory, what does it look like?
>
>  Daniel
>

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Re: v4l2_pix_format doubts

[Daniel Glöckner]

On Tue, Jun 17, 2008 at 03:52:25PM +0530, Veda N wrote:
> I think you got confused by RGB and YUV.

I don't think so

> The device is capable of giving RGB and YUV data. This is done by a
> setting in the sensor register.

That's what I wanted to know

> Now, i know what i should set the pix->pixelformat, but what about
> other members of the
> v4l2_pix_format structure.

for 640x480
width = 640
height = 480

If you tell me pix->pixelformat, I can tell you the minimum bytesperline.
It may be larger if your hardware requires padding of lines.

  Daniel

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Re: v4l2_pix_format doubts

[Veda N]

Hi Daniel,

Thanks for your quick response.

 1) I am having a pixel format (UYVY)
 2) RGB565

Thank you.

Regards,
sriram

On Tue, Jun 17, 2008 at 4:16 PM, Daniel Glöckner <daniel-gl@gmx.net> wrote:
> On Tue, Jun 17, 2008 at 03:52:25PM +0530, Veda N wrote:
>> I think you got confused by RGB and YUV.
>
> I don't think so
>
>> The device is capable of giving RGB and YUV data. This is done by a
>> setting in the sensor register.
>
> That's what I wanted to know
>
>> Now, i know what i should set the pix->pixelformat, but what about
>> other members of the
>> v4l2_pix_format structure.
>
> for 640x480
> width = 640
> height = 480
>
> If you tell me pix->pixelformat, I can tell you the minimum bytesperline.
> It may be larger if your hardware requires padding of lines.
>
>  Daniel
>

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Re: v4l2_pix_format doubts

[Daniel Glöckner]

On Tue, Jun 17, 2008 at 08:45:21PM +0530, Veda N wrote:
>  1) I am having a pixel format (UYVY)
>  2) RGB565

In both cases
bytesperline=2*width;
(minimum)

  Daniel

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Re: v4l2_pix_format doubts

[Veda N]

Hi,
Thank you for your response.

Does this value depend on any way of bpp (bits per pixel?)

If so, how?

-- 
Regards,
N. S. Veda




On Tue, Jun 17, 2008 at 10:54 PM, Daniel Glöckner <daniel-gl@gmx.net> wrote:
> On Tue, Jun 17, 2008 at 08:45:21PM +0530, Veda N wrote:
>>  1) I am having a pixel format (UYVY)
>>  2) RGB565
>
> In both cases
> bytesperline=2*width;
> (minimum)
>
>  Daniel
>

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Re: v4l2_pix_format doubts

[Daniel Glöckner]

On Wed, Jun 18, 2008 at 08:45:05PM +0530, Veda N wrote:
> Does this value depend on any way of bpp (bits per pixel?)

Pixelformat depends on bpp.
And bytesperline depends on pixelformat, width, and the padding needed by
the hardware.

  Daniel

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