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Using Pre Filtering
You can add Pre Filtering to the capture by adding any installed DirectShow video filters to the Pre Filtering setup, the filters are added removed and re-ordered in the Filters Tab of the settings dialog.

This feature is designed to allow you to do some video processing to the video stream before it is compressed and saved to disk, this is useful for cropping etc.

Filters that come with Virtual VCR
There are a number of Direct Show video filters that come with the Virtual VCR application, they are located in the filters directory and can be installed by running the install.bat file that is also located in the filters directory.

Once installed Virtual VCR will use some of these filters to do things such as monitor the data throughput of the capture and show you the capture stats, you can also add some of these filters to the capture using the Pre Filter Settings to do things like crop the video to remove video noise around the edges of a video source etc.

Some of the filter included when used with Virtual VCR in the Pre Filter setup have persistent properties, that is these settings are saved and reloaded when you close down Virtual VCR and re open it again.

Packaged Filters
Here is a list of the current video filters that comes with the Virtual VCR application.

• Video Crop
• Colour Histogram
• Flow Meter
• Audio Scope

Pre Filter Notes
The pre filters are inserted into the Capture FilterGraph between the capture filter and the Smart Tee filter. This means that any filter added also effects the Preview as well so you can see what effect the filter had to the video in real time.

In nearly all situations it is better to do any pre capture filtering after you have captured the video footage, it is possible to do some cropping using the Video Crop DirectShow filter available as part of the Virtual VCR but apart from that due to performance it is best to do all filtering after the capture.

Please Note: (Colour Space)
When adding filters it is important that you know what type of filter you are adding, if the filter can only work on certain colour formats the intelligent connect feature of the DirectShow architecture will add the appropriate colour converter to your FilterGraph. This can have some disastrous effects to performance and quality.

Example:
If you add a filter that only accepts RGB24 and the capture format is set to YUY2, the FilterGraph will add a colour space converted to convert from YUY2 to RGB24. This will cause performance issues and percussion issues.

To see what filter graphed has been built connect to the running app using GraphEdit and look for colour space converters etc.