In Layman's Terms Please Explain the CD/DVD Related Upper and Lower Registry Filters?

Windows 2000/XP/Vista provides a layered approach to device drivers. That is, a device driver developer can write a filter driver that sits above or below a function driver.In our case, we are checking for filter drivers above and below any Disk Drives and CD/DVD devices detected on your system. A developer can install their filter driver to filter I/O activity for all Disk/CD/DVD devices (e.g. Class filter), or on a per device basis (e.g. Device filter).

The driver can be specified as a lower filter or upper filter. IRPs (I/O Request Packets) are sent down the I/O stack, and processed by these filter drivers, in the following order: Upper class filters Upper device filters Function driver Lower class filters Lower device filters Bus driver/filters Filter drivers are often used to extend or alter the normal capabilities of Microsoft's CD/DVD device driver (function driver). For further information on this topic, we recommend you research Microsoft's Windows Driver Model (WDM).

Check out our links page for additional reference material. " In (sort of) layman's terms, they are layers of software that interact with a device attached to the operating system. Upper filters act on I/O signals above the function driver (it affects the I/O activity before it gets to the function driver).

Lower filters act between the function driver and the bus driver. Class filters act on ALL devices of a type, whereas the device filters are device-specific.So what happens is that when a software is uninstalled and doesn't remove the filters properly, or the filters are corrupted (during installation or operation), the device I/O stream no longer works properly, so the OS is no longer communicating with the device. For this reason, CD and DVD devices disappear sometimes altogether from the Device Manager or sometimes just quit working.

This happened in the past very frequently, in my personal experience with Roxio and Adaptec products a lot, and apparently iTunes causes it frequently now. If you remove the (in)correct filter registry, you can fix the problem sometimes. Various MS articles mention the upper and lower filter registry entries, but there is no given set of upper or lower filters that are universal to an XP system, that I'm aware of.

They will depend on the software you have installed. Also, you may have an upper filter without a lower or vice versa. Depends on the software.

Obviously, when upgrading to XP, a filter may not be XP compatible, and can therefore stop working right. The registry keys are not filters themselves, but pointers to drivers, as I understand it.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.