From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx2.redhat.com ([66.187.237.31]:42656 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751586AbZFCI5m (ORCPT ); Wed, 3 Jun 2009 04:57:42 -0400 Message-ID: <4A263B42.1010006@redhat.com> Date: Wed, 03 Jun 2009 10:58:42 +0200 From: Hans de Goede MIME-Version: 1.0 To: Erik de Castro Lopo CC: linux-media@vger.kernel.org Subject: Re: Creating a V4L driver for a USB camera References: <20090603141350.04cde59b.erik@bcode.com> In-Reply-To: <20090603141350.04cde59b.erik@bcode.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi, On 06/03/2009 06:13 AM, Erik de Castro Lopo wrote: > Hi all, > > I'm a senior software engineer [0] with a small startup. Our product > is Linux based and makes use of a 3M pixel camera. Unfortunately, the > camera we have been using for the last 3 years is no longer being > produced. > > We have found two candidate replacement cameras, one with a binary > only driver and user space library and one with a windows driver > but no Linux driver. > > My questions: > > - How difficult is it to create a GPL V4L driver for a USB camera > by snooping the USB traffic of the device when connected to > a windows machine? The intention is to merge this work into > the V4L mainline and ultimately the kernel. > That depends mainly on the format of the image data by the cam, if the cam sends raw bayer data, or raw yuv / rgb then this is doable, if it uses plain JPEG it is also doable. If it uses some custom compression then you need a wizzkid to crack the code. I've tried this myself, and I failed, you really need someone with the right mindset to reverse engineer a compression algorithm. Merely being a good programmer is not enough. > - How much work is involved in the above for someone experienced > in writing V4L drivers? This can vary wildly, assuming the video data format is a known one, a wild estimate would be that this takes 2 fulltime weeks (with hands on hardware access). But it could be that it takes much longer if somehow the cam is strange (or worse, like buggy). > - Are there people involved with the V4L project that would be > willing to undertake this project under contract? > Your welcome to send me a couple of cams, that is usually all the payment I expect, I also don't make any promises (I do this on top of my dayjob). But first things first, what are the usb-id's of the cams, can you send me (offlist) the windows drivers ? Chances are the chipset used is already supported. Regards, Hans