On Wed, Oct 13, 2021 at 10:51 PM Michael Koch <astroelectro...@t-online.de> wrote:
> Am 12.10.2021 um 19:29 schrieb Michael Koch: > > Am 12.10.2021 um 18:52 schrieb Paul B Mahol: > >> On Tue, Oct 12, 2021 at 10:55 AM Michael Koch > >> <astroelectro...@t-online.de> > >> wrote: > >> > >>> I have a question about the "fftfilt" filter. What's the default value > >>> of the weight_U and weight_V options? I'm asking because I get an > >>> unexpected result. > >>> > >>> This command line creates my input image for testing: > >>> > >>> ffmpeg -f lavfi -i color=black:s=300x50 -lavfi > >>> > drawgrid=c=white:y=-1:w=2:h=51,split[a][b];[b]crop=iw/2:x=0,scale=2*iw:ih:flags=neighbor,split[b][c];[c]crop=iw/2:x=0,scale=2*iw:ih:flags=neighbor,split[c][d];[d]crop=iw/2:x=0,scale=2*iw:ih:flags=neighbor,split[d][e];[e]crop=iw/2:x=0,scale=2*iw:ih:flags=neighbor,split[e][f];[f]crop=iw/2:x=0,scale=2*iw:ih:flags=neighbor[f];[a][b][c][d][e][f]vstack=6,split[h][v];[v]transpose[v];[v][h]hstack > > >>> > >>> > >>> -frames 1 -y test.png > >>> > >>> This is the fftfilt lowpass example from the official documentation: > >>> > >>> ffmpeg -i test.png -vf fftfilt=dc_Y=0:weight_Y='squish((Y+X)/100-1)' -y > >>> out1.png > >>> > >>> Problem: The output has a greenish tint. > >>> > >> Expressions by default for U and V are copied from Y if are unset. > >> filter works only in YUV or gray space thus in above combination one > >> gets > >> green tint. > > > > I'm trying to make the filter's cutoff frequency independant of the > image size. But that's not so easy because I don't know the size of the > FFT array. It's calculated in vf_fftfilt.c lines 185 and 297. > This calculation is difficult (and slow) to replicate in an expression, > because either a loop or a logarithm is required. > Would it be possible to add two new variables so that the FFT array size > can be used in an expression? > ARRAY_H = 1 << rdft_hbits > ARRAY_V = 1 << rdft_vbits > It the array size is known, things would become much easier. > What are you attempting to do? > Thanks, > Michael > > _______________________________________________ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".