[FFmpeg-user] denoise after scaling or before?

[Paul B Mahol]

On 4/24/19, Michael Koch <astroelectronic at t-online.de> wrote:
> Am 24.04.2019 um 10:43 schrieb Ulf Zibis:
>> Am 23.04.19 um 11:43 schrieb Jon bae:
>>> Makes it a different when I denoise after scaling a video, or is the
>>> quality better when I denoise before scaling.
>>>
>>> In terms of speed it would be better for me, denoising after scaling, but
>>> when the quality is better, then I would go that way.
>> If I see this correctly, most denoisers define a spacial area to work on.
>> So denoising before downscaling in the end will affect a smaller spacial
>> area then in opposite order.
>
> What are the pros and cons of the 8 available denoisers?
> Which of them is the best choice for which purpose?
> Are there any recommendations?
> I did try a few of them (but not all) and found that atadenoise is good
> for high-ISO videos of the night sky. This testing is very time
> consuming because most denoisers have several parameters that must also
> be optimized.

atadenoise: very fast, temporal only with no motion compensation; LGPL
hqdn3d: fast, both spatial and temporal, does basically lowpass by
destroying high frequencies, blurs with extreme settings; GPL
nlmeans: very slow, currently implemented as spatial only, algorithm
considered as one of the state of art denoisers; LGPL
bm3d: very very slow, currently implemented as spatial only, algorithm
considered as one of the state of art denoisers; LGPL
vaguedenoiser: slow, spatial only, pretty good, wavelet; LGPL
dctdnoiz: very very slow: spatial only, blurs too much; LGPL
fftdnoiz: slow, spatial and limited temporal, using Fast Fourier
Transform, may have introduce ringing with bad settings; LGPL
owdenoise: very very very slow, spatial only, wavelet; GPL
removegrain: fast, spatial only, limited usecase