Re: the focus terms or sequences

["Kim, HeungJun" <riverful.kim@samsung.com>]

Hi Laurent,

First, I hope to be good at the warsaw meeting. :)

2011-03-16 오전 9:14, Laurent Pinchart 쓴 글:
> Hi HeungJun,
> 
> On Monday 14 March 2011 08:02:01 Kim, HeungJun wrote:
>> Hi Laurent,
>>
>> I heard of that there was a chance between you and Sylwester telling about
>> the menu entries focus, and so after that, probably this menu style of the
>> patch I sent, need to be more upgraded. So, can you tell me the kind or
>> sequence of the UVC device breifly?
>>
>> I guess the word *AUTO* at the UVC device means doing focus continuously,
>> not once or one time.
> 
> That's correct. In the UVC context, auto focus means CAF and manual focus 
> means... well, manual focus :-)
> 
>> But, at the sensors I used the *AUTO* focus means doing focus once, on the
>> other hand *CONTINUOUS* means doing continuously. So, we need to be clear
>> terms about focus.
>>
>> At the sensor I used, the focus needs 3 kinds of commands:
>> 1) setting mode
>>
>>   : it makes the lens initial position for each AF(Normal, Continuous,
>>   : Night mode Focus, etc),
>>
>>     and set the AF status Idle.
>> 2) execute AF
>>
>>   : doing the move of the lens
>>
>> 3) read AF status
>>
>>   : checking the lens status(Focus failed, Focus success, Idle, Busy)
>>
>>     and do the proper jobs.
>>
>> I don't know uvc case well, so, If you share about this, it can be help.
> 
> What bothers me with your auto-focus implementation is that the user might 
> want to perform auto-focus several times. Let's imagine this use case:
> 
> 1. The user points the camera (webcam, cellphone camera, digital camera, it 
> doesn't matter) at an object.
> 
> 2. The user presses a button to perform singleshot auto-focus (it can be a 
> physical button or a button on the camera screen, once again it doesn't 
> matter).
> 
> 3. The application sets the focus control to AUTO.
> 
> 4. The driver and device perform auto-focus once. The lens is moved so that 
> the object is in focus.
> 
> 5. The user points the camera at another object.
> 
> 6. The user presses a button to perform singleshot auto-focus.
> 
> 7. The applications sets the focus control to AUTO. As the focus control value 
> was already AUTO, nothing is done.
> 
> This is clearly broken. That's why we need a V4L2 button control in addition 
> to the menu control.
> 
Yes. Youre'rignt. The menu control dosen't called one more with the same value.
It's now worked I know. But, the reason why I choose menu type for focus,
is because the menu type can let the user-application know how many kinds of
focus this sensor have & support, using querymenu. The only way letting know,
is currently the menu type.

On the other hand, not-working twice or more executions is handled by user-application.
The user-application want twice auto focus, it calls AUTO-Manual-(or any other control
value)-and AUTO once again. It's wierd, but It can satisfy application and drivers.

And, but it might be irrelevant, the user-application(or upper layer platform) can
determine how to draw & arrange the UI objects after it knows the kinds of focus
method at last.

It may be a time to need another type of control. And such control should satisfy these:
1. letting the user-application know how many kinds in the controls(like a querymenu)
2. being available to be called one more.

How about your opinion?

Regards,
Heungjun Kim