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Re: [pwc] Simplification of buffer handling

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Subject: Re: [pwc] Simplification of buffer handling
From: Jeff Cunningham <>
Date: Thu, 13 Dec 2007 08:06:17 -0800
Hi;

I haven't heard from anyone on this. Is this project still active? I 
would think someone would be interested in improvements to the driver.

--Jeff


Jeff Cunningham wrote:
> Hi;
>
> I've gotten a little positive and no negative feedback on the changes I 
> made to PWC (posted a couple weeks ago). I'd like to submit my changes 
> to the code base. Would this be the forum for doing so?
>
> To recapitulate, my goal was to reduce the latency which occurs when 
> snapshots are taken. Prior to my modification, the oldest frame in the 
> buffer list would be returned. I have added an ioctl mode which causes 
> the youngest frame to be returned instead, and the older frames to be 
> discarded. I also implemented another ioctl mode which waits until a 
> frame is finished being captured before returning, allowing one to sync 
> to the camera's clock, rather than trying to work the other way around. 
> This is independent of the existing sync ioctl used in mmap operations 
> and can be used whether actually reading a frame or not.
>
> In the process of implementing these changes, I believe I significantly 
> improved the frame buffer handling. both by simplifying it and thus 
> making it possible to run faster on slower hardware. I have tested these 
> changes on Intel PC's (both AMD and an Intel mini-ITX), and on an ARM-9 
> sbc. I have only tested them with a Philips 900NC camera, but nothing I 
> did should affect other devices so far as I can see.
>
> I modified three files: pwc.h, pwc-if.c and pwc-v4l.c.  A tarball of the 
> modified code set can be obtained from:
>
> http://cunningham.homeip.net/code.html
>
> Regards,
>
> --Jeff Cunningham
>
>
>   
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