Date: Tue, 16 Sep 1997 21:20:22 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: lamaster@george.arc.nasa.gov Cc: multimedia@FreeBSD.ORG Subject: Re: X11 video grabber for vic... Message-ID: <199709161920.VAA06208@labinfo.iet.unipi.it> In-Reply-To: <199709162004.NAA00339@george.arc.nasa.gov> from "lamaster@george.arc.nasa.gov" at Sep 16, 97 01:04:17 pm
next in thread | previous in thread | raw e-mail | index | archive | help
> If I understand your criticism of the broadcast, vic actually well actually the broadcast only triggered my desire for a better method of transmitting slides prepared in advance. Of course if there is no docs prepared in advance, you are out of luck. I was just assuming that in some way the slides could be dumped to an X window for further use. > > Some time ago I started writing an x11 grabber for vic ... > > Do you mean a function that would grab an X11 window as a frozen > frame, or a changing series of frames? I sure I'm missing something > here, but, is this a totally separate question to the above, or it is, sorry for the confusion... > somehow related? I don't remember what nv did, but, if the nv did have an X11 grabber which worked really well since you could pick anything was on the screen, either a fixed window, or the area around the cursor etc. One problem I see with a program like vic which does its own data acquisition from the device is that it does not allow you to edit the matherial. E.g. in some cases you would like to have the full-screen image from the camera, or a small 'icon' in the corner of a bigger slide, or effects with an artificial background with a live image superimposed, etc. Of course you can do these things in the device driver, or in a process between the driver and the videoconferencing program; but, because of the typical resolution in use, and the fact that more often than not access to frame grabbers is through mmap()ed regions, it seems to me reasonably efficient to have a separate 'editing' program which can prepare the image on screen the way you like, and then just let the videoconferencing program select one of the available windows. Also for demos this is quite useful: you can capture the live output from some program by just moving the mouse to the new position, etc. > problem is that the presenter doesn't have computer-available > slides to begin with, I don't understand how an X11 grabber will > help. What format would the original material be in. Not postscript, Suppose the original matherial is not available electronically. The operator at the camera could just instruct the editing program to freeze the best image and let that one go through, or let it go live when the speaker is being filmed, etc. etc. You can of course put all of this in the videoconferencing program, but why bother, since these are in a sense orthogonal features (I know not completely, there is the quality/fps issue but that could also be made adaptive, e.g. the threshold could be lowered when the traffic goes down and increased when it goes too up...) ? Cheers Luigi -----------------------------+-------------------------------------- Luigi Rizzo | Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it | Universita' di Pisa tel: +39-50-568533 | via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 | http://www.iet.unipi.it/~luigi/ _____________________________|______________________________________
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199709161920.VAA06208>