Gstreamer provides additional video and audio codec support to Windows applications running through Crossover.
You will first need to install the 32 & 64-bit Gstreamer packages on Linux.
These libraries need to be installed before a bottle is created in Crossover for the Windows app you want to use.
Next you need to edit the registry of the bottle you want to enable Gstreamer on, and set the registry key
[HKLM\Software\Microsoft\Windows NT\CurrentVersion\MCI Extensions] "avi"="MPEGVideo"
After that Windows applications in that bottle should be able to interface with Gstreamer to handle more multimedia formats.