Wednesday, February 18, 2004

VDub Filtering

Well, for relatively clean sources, where I only want to get rid of a touch of noise, it looks like VirtualDub's "Temporal Smoother" at strength 3 to 5 followed by the "Smoother" filter at strength 5 to 10 works very well. Throughput on my AthlonXP 2600+ is around 18-20fps. The temporal filter seems to do a good job of steadying up an image. In certain cases, you may want to really dial-back the smoother filter (3-5 or even disable it, just using the temporal smoother).

It also does wonders for the resulting bitrate. Encoded with TMPGEnc VBR 2-pass, with a target of 6000kbps, the resulting output is more like 4500kbps which allows me to pack a lot more on a disk (a touch over 2 hours). Normally, when I encode at 6000kbps in TMPGEnc, I only get 92 minutes per tape (enough to fit 2 episodes of Law and Order for instance if I cut commercials). However, unlike broadcast TV, the signal that I'm playing with at the moment has large black borders on all 4 sides that I've filled to solid black. Only the center 80% has a signal. That probably accounts for a good portion of the 33% change in bitrate.

Klaus Post's Smart Smoother HQ also works well. When I encoded some anime/cartoons earlier, I got better results using the Smart Smoother at "5 / 100 / 254/ 0 / weighted / withdifference" then I did with the temporal filter + smoother. Downside was the long cleanup time in VirtualDub (8fps or so). I may play around with trying to use just "average pixels" instead of weighted.

Update: Using the HiQ filter with just average ("with difference" is off), radius 7, threshold of 10 I get 15-18fps on my AthlonXP 2600+ (352x480 30fps source). That's competitive with my original temporal+smooth method. For cell drawn anime 7/10/average/nodiff seems to give very good results. Increasing the radius to 9 or 11 makes things a bit flatter but would also slow it down.

Update #2: I'm finding that I dislike what the "Smoother" filter does to the output at strength 10-20. The last VHS capture that I did was 352x480 with simply using "Temporal Smoother" at strength 5. I still may try the smoother at some lower single-digit values, or combine it with a sharpen filter.

posted by Wuphon's at 9:05 AM