From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n6OGAOKE009759 for ; Fri, 24 Jul 2009 12:10:25 -0400 Received: from mail-bw0-f216.google.com (mail-bw0-f216.google.com [209.85.218.216]) by mx3.redhat.com (8.13.8/8.13.8) with ESMTP id n6OGA8Kv013856 for ; Fri, 24 Jul 2009 12:10:08 -0400 Received: by bwz12 with SMTP id 12so1493215bwz.3 for ; Fri, 24 Jul 2009 09:10:08 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20090724124825.672be2d3@pedra.chehab.org> References: <20090717174101.GB15611@vanheusden.com> <20090723165929.64cf3933@pedra.chehab.org> <20090723201823.GS11865@vanheusden.com> <36c518800907240758k2a1d8e9btdd841323e4dc2492@mail.gmail.com> <20090724150727.GB11865@vanheusden.com> <20090724124825.672be2d3@pedra.chehab.org> Date: Fri, 24 Jul 2009 19:10:07 +0300 Message-ID: <36c518800907240910m93f253cv19efbdf489e0fb1e@mail.gmail.com> From: vasaka@gmail.com To: Mauro Carvalho Chehab Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Cc: video4linux-list@redhat.com Subject: Re: video4linux loopback device List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: video4linux-list-bounces@redhat.com Errors-To: video4linux-list-bounces@redhat.com List-ID: On Fri, Jul 24, 2009 at 6:48 PM, Mauro Carvalho Chehab wrote: > Em Fri, 24 Jul 2009 17:07:29 +0200 > Folkert van Heusden escreveu: > >> > >> > Any chance that the video4linux loopback device will be integrated in >> > >> > the main video4linux distribution and included in the kernel? >> > >> > http://www.lavrsen.dk/foswiki/bin/view/Motion/VideoFourLinuxLoopbackDevice >> > >> > or >> > >> > http://sourceforge.net/projects/v4l2vd/ >> > >> > or >> > >> > http://code.google.com/p/v4l2loopback/ >> > >> > This enables userspace postprocessors to feed the altered stream to >> > >> > applications like amsn and skype for videochats. >> > >> If the postprocessor application is LGPL, the better is to add it at libv4l. >> > > >> > > I don't agree as the postprocessor implements fun-effects: warhol, >> > > puzzle, circles, wobble, etc. >> > >> > and how one can make skype to get pictue from libv4l or alter the >> > picture which application is getting through libv4l? >> > again some proxy is needed here. >> >> Correct so we definately need some external video loopback device. >> It gives as a much greater flexibility. > > libv4l intercepts V4L2 calls by using LD_PRELOAD. Without it, skype doesn't > work with most of the cams, since it doesn't support several of the output > formats common on most cameras. I have lots of different webcam models here. I > think only one or two are directly supported by skype. > > libv4l already have some postprocessor effects (currently limited to image > enhancements like auto-gain/auto-bright and similar stuff), but I don't see why > not adding there other effects including the fun ones. > > Hans has several plans of improvements for it, including more post-processing > effects and the ability of duplicating a video to more than one application at > the same time. > > The big problem with a v4l2 loopback is that you're adding something that it is > not proper to kernel, since it were not designed to be a proxy between two > userspace applications. This is the space where libraries were designed. Due to > that, you can affect the machine performance, due to the usage of kernel memory > barriers. > > Also, you'll likely add extra buffering costs of copying control data and > stream mapping in order to access it  from/to kernel where you could just pass > a buffer between the effect processors and do a simple function call. > > > > Cheers, > Mauro > Sounds interesting. will libv4l have ability to provide video from sources other than v4l2 devices? One of the things I want to achieve is to provide talking head to video chatting programs instead of usual video stream. vasaka -- video4linux-list mailing list Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list