Re: [GnomeMeeting-list] [PATCH] Better integration with Video4Linux for PWLIB



Am Dienstag, 23. September 2003 00:17 schrieb Derek Smithies:

> <rant>
>  One of the goals of linux people the world over is to replace MS with
> Linux. This is fine. Consequently, for linux to be usable by the masses,
> things like cameras, programs, drivers etc have to be installed simply.
> No requirements for fiddling around with new kernels, editing conf files,
> building from source.
>
> It should be
>    rpm -Uvh gnomemeeting.rpm
>    gnomemeeting
>
> Now, cameras (usb ones in particular) are easy to install. Just plug it in.
> Non usb camera may require a grabber card.
>
> You see - just plug it in and it goes. This is what the Microsoft
> interface is aiming for.
>
> In the four years that I have been involved in openh323, reading the
> list, helping people,
> my view is the biggest pain in the ass is camera and sound.
>
> Buggy drivers, (drivers that fail to meet the spec)
> Authors who say, my driver meets the spec - it works with xawtv.
> This is  a stupid and obnoxious comment.

But unfortunately pwlib is not following the spec. The spec can be found in 
the kernel sources (for me, this is 
/usr/src/linux/Documentation/video4linux/API.html), and citing from it:
---
|  The minimum and maximum sizes listed for a capture device do not imply all
|  that all height/width ratios or sizes within the range are possible. A 
|  request to set a size will be honoured by the largest available capture
|  size whose capture is no large than the requested rectangle in either
|  direction. For example the quickcam has 3 fixed settings.
---
This means, the driver can choose any smaller size, as the maximum size may 
depend on other circumstances, as frame size or colour format ...

Citing further:
---
|  A successful call to VIDIOCSWIN indicates that a suitable set of parameters
|  have been chosen. They do not indicate that exactly what was requested was
|  granted. The program should call VIDIOCGWIN to check if the nearest match
|  was suitable. 
---
So the correct solution is to ask for a size, see, what we get, and, in the 
case of pwlib, choose an appropriate converter.


> STOP the crap software. fix the driver. make the driver meet the spec.
> work harder. get it right.
>
> openh323 is criticised because it does not work. Why does openh323 not
> work? Cause the driver writer did not do his/her job correctly.

Sorry, IMHO pwlib is just not following the spec ...

> I don't want to know about adding extra options to conf files. The default
> option should always work.
>
> If linux video and sound drivers cannot work "out of the box", then there
> is no hope of overtaking microsoft.
>
> Yes, I know that microsoft code has many drivers that "don't work right".
> That is no excuse.
> The goal for linux is for all drivers to work.
> If we can achieve that goal, linux has a chance.
>
> </rant>
>
>
> Derek.
>
> P.S. sorry for venting/ranting, but I am sick of substandard driver code.
>     it wastes so much developer time, getting applications to work with
>      buggy drivers.

So lets just follow the specs (driver and application developers), so we can 
proof that something is wrong, making the life just easier for everyone.

Greetings,

Stefan

PS: The proposed behaviour for drivers in case of inappropriate size request 
will be the same for v4l2!
-- 
Stefan Brüns  /  Kastanienweg 6 - Zimmer 1206  /  52074 Aachen
mailto:lurch gmx li  http://www.kawo1.rwth-aachen.de/~lurchi/
   phone: +49 241 169-4206     mobile: +49 160 7532733 

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