可能有一段差距
Q What are the differences between the three most common digital comb filters: 1) Digital Comb Filter; 2) Digital 3-Line Comb Filter; 3) Digital 3D Y/C Comb Filter.

A 1. A digital comb filter is one where the signal is routed through an A/D converter, then the separation is performed in the digital domain, and then the signal is routed through a D/A. If the A/D is not clean, this is a step where the picture quality can be degraded. The good news is that most such filters do a good job in this area.

2. A line 3-comb filter is also called a 2D digital comb filter. Both the Faroudja and Audio Alchemy filters are this type, and most other digital comb filters are this type. The process looks at the previous line and next line to determine what is the best way to separate the Y and C. Hence 3-line.

3. A 3D filter is a temporal filter. What it does is look ahead at the next field. (there are two fields for every frame of video, one field is the odd # lines and the other field is the even # lines from 1 to 525.) It then compares and separates accordingly. The problem with 3D filters is determining when to do field (3D) or line (2D) level comparing. The logic here is far from perfect and often introduces decoding errors. It works great on static images, but when there is motion, it must revert back to a 2D comb filter. So a 3D filter is both a 3D and 2D filter in one. Because of the cost of memory required to do 3D filtering, they often cut costs on the 2D portion, which, unfortunately, does most of the work.

詳細技術資料請參考
http://members.aol.com/ajaynejr/vidcomb.htm