Denoise3D in FFDShow

[Beak]

Hello. I hope this is posted in the correct section.

I have read this filter is adapted from an avisynth filter

I was hoping someone could explain the limitations and benefits of this filter, and the relative effects of the available settings which are Luma, Chroma, and Time.

I am attempting to filter light noise from blu=ray content prior to compressing to AVCHD. So far I have been using the default settings which are Luma 4, Chroma 3, and Time 6.

Thanks in advance for any help.

[MadRat]

Gee, I wish I could help you Beak but I haven't heard anything about Denoise3D. I hate to pass he buck but I'd say the first thing to do is go to the ffdshow guys and ask them what filter they were using. They may have even modified an avisynth filter beyond recognition.

[lych_necross]

Denoise3D was ported from a MPlayer filter with the same name. It was also ported to Avisynth a while back. In all cases, the functionally remains the same. Here is readme from the Avisynth port:

HQDN3D 0.11 by Loren Merritt, Copyright 2005.
Based on the MPlayer filter with the same name, by Daniel Moreno.

High Quality DeNoise 3D is an Avisynth 2.5 filter.
It performs a 3-way low-pass filter, which can completely remove
high-frequency noise while minimizing blending artifacts.


Notes:
Due to the linear nature of this filter, combined with the need to make the
result of a given frame independent of seeking, hqdn3d will run very slowly if
you continually request frames out of order.
However, when operating linearly, it can process 720x480 at about 80fps
on my Barton 2500.

This filter works only in the YV12 colorspace, simply because I haven't
bothered to code a YUY2 version.


Usage:
hqdn3d(clip, float ls, float cs, float lt, float ct, int restart)

ls: (default=4.0)
luma spatial filter strength.
cs: (default=3.0)
chroma spatial filter strength.
lt: (default=6.0)
luma temporal filter strength.
ct: (default=4.5)
chroma temporal filter strength.
restart: (default=lt+1)
Whenever a frame is requested out of order, restart filtering this many
frames before. While seeking still slightly affects the content of the frames
returned, this should reduce the disturbance to an unnoticable level.

Filter strengths vary from 0 (no filtering) to 255 (there will be nothing left
of your video).
If any options are omitted, they will assume a value based on any other
options that you did specify. For example, hqdn3d(2) is equivalent to
hqdn3d(2,1.5,3,2.25).

[MadRat]

Oh HQDN3D, I've heard of it but I haven't used it. I can tell you what most of the terms in the settings mean if that's any help.
The video has two parts, bright/dark and color. The bright and dark part (the intensity level) is called luma and the color part is called chroma. If you try cleaning the luma too much you'll start loosing details in your video. If clean the chroma too much you'll get color banding. Color banding is where the colors won't change smoothly from one to another (like from light blue to a darker blue in the sky) but look like strips or bands of colors (http://en.wikipedia.org/wiki/Color_banding). You can remove a lot more noise from the chroma than from the luma before you start noticing problems.
3D denoise filters work in two ways: they remove noise from each frame and they remove noise by comparing several frames. Removing noise from just one frame is called spatial filtering. Removing noise from several frames in a row is called temporal filtering (temporal means things that have something to do with time).

ls means how much noise to remove from the bright and dark level of each frame by itself
cs means how much noise to remove from the color part of each frame by itself
lt means how much noise to remove from from the bright and dark level of each frame by comparing several frames
ct means how much noise to remove from the color part of each frame by comparing several frames

[royia]

Does this algorithm has a feature to preserve edges?

Moreover, it says it works only on YV12, does it mean I should do something before I use it on AVI file?

Thanks.