[FFmpeg-user] ffmpeg noise command: How is noise level defined

[Paul B Mahol]

On 10/22/13, Armin Kappeler <arminkappeler2011 at u.northwestern.edu> wrote:
> Hi Lou,
>
> Thank you for the reply.
> Maybe I have to clarify. My code works fine, I don't have a question about
> an error message. It is information, that I need for my conference paper.
>
> I am referring to the following part of the documentation in section 9.53:
> *Set noise strength for specific pixel component or all pixel components in
> case all_strength. Default value is 0. Allowed range is [0, 100].*
> *
> *
> I added noise of different strength to my video with the following commands
> (4 examples):
> ffmpeg -i vid1.avi -vf noise=alls=0:allf=t -vcodec libx264 vid2.avi
> ffmpeg -i vid1.avi -vf noise=alls=25:allf=t -vcodec libx264 vid2.avi
> ffmpeg -i vid1.avi -vf noise=alls=50:allf=t -vcodec libx264 vid2.avi
> ffmpeg -i vid1.avi -vf noise=alls=100:allf=t -vcodec libx264 vid2.avi
>
> Here I choose 4 different noise levels (0,25,50,100).
> My question is now, how much noise is added to the video in each case?
> One possibility is e.g. this:
> For gaussian noise, the noise level corresponds to the variance of the
> gaussian noise (-> variance 0 = no noise)
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The strength sets amount of noise added to pixel and amount of pixels
that have noise added.

Thus 0 for strength should return unmodified video.