Is this a framebuffer job?

Tormod Volden lists.tormod at
Thu Nov 7 13:44:46 PST 2013

On Thu, Nov 7, 2013 at 9:39 PM, Gene Heskett wrote:
> 4, throwing away the unwanted pixels should be a few lines of code,
> essentially free, and by reducing the amount of data to be processed from
> 5,000,000 pixels to 57,600 pixels gains me only .0868% times the data to
> process, which gains me many frames a second in processing speed, something
> your lens cannot not do.

This feature is called region of interest (ROI) and I would be
surprised if the V4L people are unfamiliar with that. It is a common
feature in industrical cameras and is often done directly on the
sensor chip [1]. Grepping for ROI in the Linux webcam driver source
tree indicates that the CPIA-based camera drivers have support for

Where there is no hardware support for this, it might be most
efficient to implement it in the hardware driver that pulls the image
data in over USB and decompresses it before exposing it to the V4L
stack etc. But a general software ROI functionality would fit
perfectly in V4L IMHO.



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