In order for Dvbdream to show a codec as availble to use, you have to add the codec's CLSID number to Dvbdreams guids.ini file.
So let's say I want to add "DivX H264 Decoder Filter" to the guids file.
1) I use DirectShow Filter manager to display information about the codec filters I have installed.
2) Next I locate the codec filter I want to use form the list in DirectShow Filter Manager, and double click the line for that codec. This open the codec's properties page.
3) Then you open the guids.ini file with notepad (select all files type in notepad, while browsing for guids.ini). Each type of filter has it's own section in the guids file, I.E. Audio, Video and H264. So I add my new entry at the end of the existing H264 section. H264codec9 was in use, so the new entry becomes H264codec10
4) Between the Codec Properties Page and Guids.ini, cut and paste the following informatiom. IE. (my example)
H264codec10="name of codec filter from properties page", {CLSID number from properties page}
Note any lines starting with a semi-colon in the guids file do not get read. Don't add a codec after a line with a semi-colon or it will not get read.
Note there is no space between codec name and the = sign
Note there is a coma after the name of the codec and one space before the CLSID number, which is in {} brackets.
5) Save the changes to Guids.ini (under the "file" menu of notepad).