Merging original PRORES and converted to h264 content: colorshift problem

[dogmydog]

Dear VH fellows,

I have a lot of h264 15mbps mp4 documentaries with burnt in subtitles that I need to reexport clean versions without the burnt in subtitles, but leaving the burnt in lower thirds (names and functions of every interviewee).

I have the textless original files in PRORES, but they are pure textless.
Meaning that I would have to re-edit these files to burn in the needed lower thirds.

To avoid having to re-edit the PRORESes, I tried to merge them with the h264 converted files, cropping about 20% the bottom to erase the subs and keep the lower thirds. However, when I export using Adobe Media Encoder, I get a color shift and a crop line dividing the two assets (see how the red on the map is divided):


[Attachment 65890 - Click to enlarge]

-- Remember that these converted h264 files were originally the exact same PRORES with burnt in subs and lower thirds, exported in 2019, 2020, with Adobe Media Encoder. --

I tried converting the PRORES to h264 to see if the color would match, but it produced a new h264 with different color than the old texted one.
Therefore the merging results are exactly the same.

I wonder if you could help me avoid this color shift problem so I can convert the PRORES to match the h264 color?
Here are the video examples so you can analyse.
https://drive.google.com/drive/folders/1sMzc-Dl9HVz4r7UFIt7UWYzba6nrU65I?usp=sharing
-colorshift: displays the problem
-h264: fully texted h264
-prores: original textless

Thank you so much for your attention and help!

[poisondeathray]

This is a colormatrix 709 vs. 601 mismatch.

To match it, you would either convert the prores shifting from 709 to 601; or the h264 from 601 to 709.

I would find out what the "proper" color is supposed to be and use that to guide your conversion. Or if you had colorbars on some of the clips it should tell you. My guess is the prores version is "correct", and the map colour should be more orange than red

One way would be to use a 601 to 709 LUT on the h264 MP4's in PP (as input LUT in lumetri color). I've attached 601 to 709 and 709 to 601. The original author is Adam Stanislav from the Creative Cow forum

Another way would be to batch convert one of the series in ffmpeg using zscale (e.g. the h264 clips from 601 to 709). If you need more info on this method, ask

[dogmydog]

Dear @poisondeathray, the LUT worked flawlessly!
Just out of curiosity, what would be the command line for ffmpeg to batch convert the h264 to 709?

Thank you so much and best regards from Rio,

[poisondeathray]

Just out of curiosity, what would be the command line for ffmpeg to batch convert the h264 to 709?

"170m" has the same values as "601" for matrix, so the zscale filter would look like

-vf zscale=matrixin=170m:matrix=709

You could encode to h264 again, or prores, or a different format, or using whatever settings you want.

In this example, a folder of MP4's are batch re-encoded using x264 @ crf18 to (change the PATH to the destination folder you want) using a batch file. The output files also have "new" appended to the original filename (you can change it)

for %%a in ("*.mp4") do ffmpeg -i %%a -vf zscale=matrixin=170m:matrix=709 -c:v libx264 -crf 18 -c:a copy "PATH\%%~na_new.mp4"

pause

[dogmydog]

[QUOTE=poisondeathray;2662595]

for %%a in ("*.mp4") do ffmpeg -i %%a -vf zscale=matrixin=170m:matrix=709 -c:v libx264 -crf 18 -c:a copy "PATH\%%~na_new.mp4"

pause

I will try this! Tysm again!