On Mon, 26 Sep 2005, Luca Bonissi wrote:
> Make attenction: by default, the new yuvdenoise has a gaussian filter
> and a spatial filter on...
>
> I usually disable the spatial and gaussian filter (-s 0,0,0 -g 0,0,0).
> Maybe you can keep the gaussian filter for chroma only (-g 0,255,255).
It is not a good idea to dismiss those options too quickly.
When enhancing still images a well known technique is to apply a mild
blur followed by sharpening (most often with the unsharp mask filter).
Guess what? That technique works for motion pictures (video) as well.
For 'noisy' video data (and almost anything coming from the analog
domain is noisy) you can greatly enhance the visual quality by using
all of yuvdenoise's options (with moderate settings) followed by
'y4munsharp'.
'-g N,255,255' for values of N <=16 are almost identical and mild,
the effect increases slightly at N=32. It's only at 64 that the
softening becomes noticeable.
I was doing some test encoding using a DV capture of an old video
from a laserdisc. I won't bore you with the entire script (unless
you're curious ;)) but the yuvdenoise step was
... | yuvdenoise -s 3,4,4 -g N,255,255 -t 2,2,2 | \
y4munsharp | \
...
mpeg2enc -D 10 -G 12 -p --dualprime-mpeg2 -c -E -10 -f 8 -q 2
-K file=hi-tmpgenc -4 1 -2 1 -o rhrh.m2v
(hi-tmpgenc is a custom table combining tmpgenc and hi-res tables)
And I varied N thru 1, 2, 4, 8, 16, 32 and 64 and tabulated the
average bitrate of the final .m2v file. In all cases the visual
quality was excellent, at N=64 there the smallest degree of
softening beginning to be noticed. I did not try a N=128 (which
happens to be the default) though
(B frame size is 0 since I turn B frames off):
Average I Frame Size P Frame Size
N bits/sec bytes bytes
-- -------- ------------ -------------
00: 4338400 38985 21130
01: 4028000 37376 19513
02: 4028000 37376 19513
08: 4028000 37376 19513
16: 4027600 37373 19510
32: 4006800 37292 19400
64: 3876000 36727 18706
Even at the lowest bitrate the 'watchability' quality is very high.
yuvdenoise can be 'fine tuned' - I could have been a little less
agressive, perhaps '-s 2,4,4' would have given me a higher bitrate
Seems my problem these days is getting the bitrate high enough so
I don't waste space on a piece of DVD media :-)
The combination of yuvdenoise + y4munsharp is amazingly effective
at enhancing the image. And as an added bonus yuvdenoise is about 4x
faster than y4mdenoise - the speed is quite acceptable to me. For a
2hr movie (what's 8 hours of encoding time after 24 hours of render
time? ;))
Cheers,
Steven Schultz
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