In general, all software codecs produce high-quality images, provided they have been set to do so. If you need to enhance the film on the computer again, you'll need to have a codec that allows you to edit frame by frame. The best candidate for this is DV - a codec with a data rate of 3.6 MB per second, used by camcorders. Professional video editing systems also use DV to process the video later on the PC. The commercial Motion-JPEG Codec also allows frame by frame editing. Films compressed with it are only a fourth of the size of those compressed with DV. Virtual Dub doesn't open MPEG-2 files automatically; it takes the following detour: the software DVD2AVI stores the MPEG-2 source file as a new file with the extension *.D2V, which is in turn converted by Vfapiconf to an AVI file. Both programs are available at www.doom9.org . Or, if you prefer, you can download a modified version of Virtual Dub that already supports MPEG-2 streams from virtualdubmpg2.sourceforge.net.

Another alternative to DV, MJPEG and MPEG-2 is Huffyuv (math.berkeley.edu ). This free, lossless codec will compress videos in real time, even on slow 500 MHz PCs. Trouble is, you can't reduce the size of the original file by more than 50 percent.

Rock The Block With DV

Virtual Dub supports the DV codec. But because it uses the older Video-for-Windows standard, after you install the codec and make the register entries (see right column) it will only process DV type-2 films, in which audio and video data streams are separated. In DV type-1 videos, the audio and video data is combined into one stream. If you want to open type-1 videos, you'll first have to convert them with Edit Studio or a similar program. There are many places where you can get the DV codec, such as Mainconcept.

Virtual Dub users will also be happy to hear that they can download a free DV codec from Panasonic. One site offering this codec is bokova.lv . The Vfw-compatible software is installed in two steps: Windows 2000 and XP users must copy the 259 kB file pdvcodec.dll into the system23 Windows folder, then must create and import the following registry file.