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Date:      Fri, 17 May 2002 09:27:41 +0200
From:      Marco Molteni <molter@tin.it>
To:        Carlos Ugarte <cau@cs.arizona.edu>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: writing a driver for the IBM ultraport camera (USB)
Message-ID:  <20020517072741.9472.qmail@cobweb.example.org>
In-Reply-To: <15588.12506.65605.999864@pc-ugarte.research.att.com>
References:  <20020516091509.1671.qmail@cobweb.example.org> <15588.12506.65605.999864@pc-ugarte.research.att.com>

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On Thu, 16 May 2002 18:21:14 -0400, Carlos Ugarte <cau@cs.arizona.edu> wrote:

> I'm working on a similar project - a FreeBSD driver for the Philips
> webcams based on the Linux pwc driver.  It's nowhere near working yet,
> but I've learned a few things that may help you along the way.

[..]

Hi Carlos,

thanks for the detailed answer, and thanks for taking the time of
writing a real answer instead of quickly jotted words :-)

Thanks also for the suggestion on which driver to use as a starting
point.  I already thought of using USB snoopy to get a dump of the
protocol exchange.

Regarding the Philips webcam you are working on, I am wondering how you
will handle the decompression part, which as you know is done in Linux
by a binary only driver for NDA reasons.

I have a question on the USB architecture. From my limited understanding
the various USB devices are divided in "classes", for example storage,
or human interface like a mouse. Each class of device is supposed to
have a specific API in addition to the generic USB one. On the USB web
site I was able to find the class document for still video cameras, but
it seems there is nothing regarding, what's the english for it,
continuous video cameras. Are you aware of any standard for these devices?

> Further down the line there is the issue of what kind of interface
> should be provided to user space.

[..]

Exactly! I know nothing about video, but I understand it would be crazy
(or masochistic) to provide a different API per video driver. I am aware
too of video4linux, which good or bad is at least a standard. Looking
for a standard I found SANE (http://www.mostang.com/sane/) which is or
tries to be the Unix (better?) equivalent of TWAIN. Although SANE means
Scanner Access Now Easy, it talks also about video cameras.

Any ideas on this?

marco

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