[HELP] Downscaling/Resizing to ProRes 444: The Journey Begins

[Apprentice]

How does:

"/Applications/Hybrid.app/Contents/MacOS/ffmpeg" -y -threads 8 -i "/Volumes/CANON/DCIM/102_PANA/P1020699.MP4" -map 0:0 -c:a copy -sn -filter_complex "extractplanes=y+u+v[y][u][v]; [u] scale=w=4096:h=2160:in_range=full:flags=neighbor+bitexact [us]; [v] scale=w=4096:h=2160:in_range=full:flags=neighbor+bitexact [vs];[y][us][vs]mergeplanes=0x001020:yuv444p,format=pix_fmts=yuv444p10le,scale=w=1920:h=1014:flags=bicubic+full_chroma_inp+full_chroma_int,zscale=rangein=tv:range=tv" -sws_dither none -pix_fmt yuv444p10le -strict -1 -vcodec prores_ks -profile:v 4 -vtag ap4h -f mov "/Users/user/Desktop/P1020699_21_41_13_3910_01.mov"

behave?

It gave me 

[Parsed_mergeplanes_3 @ 0x7fb71e708700] input #1 link in1 SAR 15:16 does not match output link default SAR 1:1
[Parsed_mergeplanes_3 @ 0x7fb71e708700] Failed to configure output pad on Parsed_mergeplanes_3
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #0:0
Conversion failed!

But I changed the dimension "4096" back to 3840, and "1014" back to 1080, and it then went through the frames in Terminal and exported the video correctly. Thank you very much for your help! I've even learned a bit of ffmpeg command line.
The quality seems to be about the same, if even a little bit grainier, than the footage I got from simply importing the 4k MP4 into Adobe Premiere and exporting 1080 ProRes444 from there;I'm not sure if Premiere was correctly scaling the RGB data to conserve color information (4:4:4) or not, so the real test will be when I grade it. Do you know of any way to do this process easier, with or without Hybrid/ffmpeg?
Again, thank you very much! Sorry to be such a bother for just one specific feature of Hybrid.

[Selur]

Do you know of any way to do this process easier, with or without Hybrid/ffmpeg?

a. instead of installing Hybrid you could download ffmpeg from https://evermeet.cx/ffmpeg/
b. one could write a small shell script to do the job and use a few parameters to the script (like: inputFile, outputFile, inputResolution, outputResolution) so that one doesn't have to call the whole line at once.
Sadly I don't know of any application which does this sort of resizing that offers a gui for Mac OS X.
(Since I fixed the bugs related to this in my personal dev versions of Hybrid, next public release will allow to use Hybrid to do this on Linux and Windows.)

Cu Selur