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From: "Shuzhen Wang" <shuzhenw@codeaurora.org>
To: <linux-media@vger.kernel.org>
Subject: Zooming with V4L2
Date: Fri, 19 Nov 2010 15:22:23 -0800
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Sender: Mauro Carvalho Chehab <mchehab@gaivota>

Hello, 

I am working on a SOC V4L2 video driver, and need to implement zoom
functionality. 

>>From application, there are 2 ways to do zooming. The 1st way is to use
cropping and scaling as described in section 1.11.1. The application calls
VIDIOC_S_CROP to achieve zoom. The 2nd way is to use V4L2_CID_ZOOM_ABSOLUTE
and V4L2_CID_ZOOM_RELATIVE as described by Laurent in
http://video4linux-list.1448896.n2.nabble.com/RFC-Zoom-controls-in-V4L2-td14
51987.html.

Our camera hardware supports digital zoom. However, it acts LIKE optical
zoom because it doesn't do upscaling, so no video quality is sacrificed. As
a driver writter, is it okay to support only V4L2_CID_ZOOM_ABSOLUTE and
V4L2_CID_ZOOM_RELATIVE? 

I guess it also depends on how zooming is done for most of the V4L2 user
application out there. 

Your comments are appreciated.
-Shuzhen