@karl @Lpowell Could you make a template to be able to load it into GUI ffmpeg as AVANTI?. Scripts language and similars its not friendly for newbies as me. Thanks a lot

In case anyone is interested... Here is a script to defish, denoise and scale a 7,5mm Samyang Lens on GH4 UHD:

ffmpeg -i "$1" \ -filter_complex 'extractplanes=y+u+v[y][u][v]; [u] scale=w=3840:h=2160:flags=print_info+neighbor+bitexact [us]; [v] scale=w=3840:h=2160:flags=print_info+neighbor+bitexact [vs]; [y][us][vs]mergeplanes=0x001020:yuv444p,format=pix_fmts=yuv444p10le,hqdn3d=3:3:5:5,frei0r=lenscorrection:0.5:0.5:0.16:0.6,scale=w=1920:h=1080:flags=print_info+bicubic+full_chroma_inp+full_chroma_int' \ -sws_dither none \ -q 0 -quant_mat hq \ -c:v prores_ks \ -profile:v 4 \ -c:a copy \ -c:s copy \ -c:d copy \ -map 0 \ "$2/$1"

@paglez Sorry. I am running a homebrew ffmpeg compile in OSX. 1. You need to find/compile ffmpeg with frei0r plugin enabled 2. You need to find the part in the GUI where you can put in the complex filter chain (-filter_complex) 3. set your output codec for video stream and tell ffmpeg through the GUI to copy audio and metadata stream

@paglez i made the experience that GUI is not good here. And by the way (no offence): real men don't click! ;)

Even when downscaling "only" from 1080 to 720p @karl script makes files hold on well while heavy grading... but to be completely honest couldn't notice much difference when downscaling after grading; visually looked same quality. It might also be the previous added tweaking to the workflow, je je. Anyway as much as I tried I couldn't make a service script inside automator to apply karl's ffmpeg settings from the finder contextual menu and batch folders. If anyone around knows how to batch in ffmpeg from a (mac) terminal and has a bit of patience, I'm tired of reading and just feel too dumb :P

A little poopooza for closing =)

You've seen my scripts for "offline" downscaling using ffmpeg earlier in this thread.

Now today I've experimented quite a lot on how to achieve "live"/realtime downscaling while replaying 4k video on a 2k screen with very good quality. Using a software-scaler from ffmpeg is not an option for this use case, as it would simply be too slow.

Configuring hardware scalers, as available in all current GPUs, is not quite as trivial as it may seem, because down-scaling a crisp 4k picture to 2k can easily cause visible aliasing/ringing artifacts in moving pictures. After many experiments, I found that the following setting, when used with an Intel GPU and the OpenGL driver, as available from the marvellous mpv player, provides for the best visible quality - crispy sharp pictures reasonably free of artifacts:

-vo=opengl:lscale-down=mitchell:lparam1=0.3:lparam2=0.3:cscale-down=mitchell:cparam1=0.3:cparam2=0.3:scaler-resizes-only:fancy-downscaling:dither-depth=auto:fbo-format=rgba16

What I do with these options in prose is telling the OpenGL driver to (only when down-scaling) use Mitchell-Netravali filtering with a balanced parametrization on both luma and chroma pixels, and with a destination pixel format that will retain as much information as possible. (The Alpha channel in the output is not strictly needed, but it seems that more drivers support RGB with Alpha channel than without.)

Notice how above options are very different from the default options activated by choosing "-vo opengl-hq", which really don't look good when down-scaling 4k to 2k.

Luckily, one can use the above options while still using hardware h.264 decoding and the scaling stuff is done by the GPU, so I end up with only ~5% CPU consumption when replaying a 4k video on the 2k screen of my laptop.

(For more on the video output and scaler options available in mpv read on here.)

Hi! I've read thru this topic and just thought to invite everyone to try our plugin for ae and premiere called GPUResize.

You might consider it useful - it's really fast and it does gpu accelerated downscaling and upscaling using almost all actual algorithms, from nearest to convolution stuff like lanczos/kaiser. (I really hope that's ok to post such things here, Vitaliy?) Comments and suggestions are very welcome!

Just checked - it's all there. Well, this zip was downloaded and used several times already =) Zip file contains plugin_mac and plugin_windows folders with plugin binaries for osx/win, you're expected to manually copy content into Ae/Pr (described in readme.txt file and pdf).

Doh! It was actual 7z data in the .zip named file. :[ Reuploaded now, sorry.

@LPowell: To top it off, when you try to register an account on the Infognition user support forum, it trolls you with an unintelligible verification image:

http://forum.infognition.com/index.php?action=register

If you are still interested, the answer is quite simple: if you step through that very complicated formula (no need to solve it, nor did I bother) you only see 4 digits, so there's your answer: 4.

I've just registered.

I have read this thread with great interest, as I have been trying endlessly to downscale HD to SD (1920x1080 to 720x576). I have achieved great results in every aspect accept in the gamma / chroma / color shift area, in which I either get a color shift or very small green blotches. This is what I am currently using, which is producing very small green blotches.

ffmpeg -i /Users/myself/MOVS/source22.mov \ -map 0:v -vf colormatrix=bt709:bt601,scale=720:576:flags=lanczos \ -map 0:1 \ -map 0:2 \ -map 0:3 \ -map 0:4 \ -map 0:5 \ -map 0:6 \ -map 0:7 \ -map_channel 0.1.0:0.1 \ -map_channel 0.2.0:0.1 \ -map_channel 0.3.0:0.1 \ -map_channel 0.4.0:0.1 \ -map_channel 0.5.0:0.1 \ -map_channel 0.6.0:0.1 \ -vcodec prores_ks -profile:v 3 -vtag apcn -f mov -c:a pcm_s16le /Users/myself/MOVS/source22_Done.mov

Wonder if someone here can guide me or point me in the right direction of downscaling from 4k to 1080p 10bit in ffmpeg using a colour channel such as green into one of the 10bit formats in grayscale such as gray10le? As a side not in my experiments with ffmpeg I get nearly the same file sizes as in colour such as prores and yuv444. I was hoping using only one channel in grayscale would have some benefit in filesizes for editing.. Thank you in advance for any replies