[Cin] HDR footage from images via ffmpeg

Andrew Randrianasulu randrianasulu at gmail.com
Wed May 31 21:35:35 CEST 2023

ср, 31 мая 2023 г., 14:09 Andrea paz <gamberucci.andrea at gmail.com>:

> > is HDR basically "some 8 or 10 bit tech + wide gamut light emitting"?
> I am not familiar with HDR. All I know is theoretical and dated
> (Brinkmann's book on compositing).
> HDR can only be in floating point, using a normalized color range (0-1
> instead of 0-255, etc.). In fact in floating point it is possible to
> have values above 1 while in 8, 10 -bit it is not possible to have
> values above the limits.
> Upon receiving an HDR video signal, there are algorithms to map and
> balance these values on SDR or HDR displays. This is called tone
> mapping.
> To summarize it is necessary:
> 1- An HDR video signal (usually obtained by merging multiple frames at
> different exposures).
> 2- A tone mapping tool
> 3- A suitable display (usually high nits, i.e., brilliance)

So, may be due to 1) modern smartphones have so many cameras!

I am looking at shotcut forums just for inspiration



Any editor working in HDR needs to be able to import BT.2100 HLG, BT.2100
PQ, BT.2020 and BT.709 files and map them to a common timeline format,
output to those 4 formats, and allow the user to calculate the HDR10
metadata if you choose to have a PQ output format (this isn’t automatic as
you need to know the gamut and peak brightness of the monitor you edited



=== quote ===

*HDR Support (x264 & x265):*

*Tagging DCI-P3:* --master-display

*Tagging BT.709:* --master-display

*TaggingBT2020:* --master-display

The L(?,1) indicates lux ratio (e.g., 1000:1). This value has no standard
and needs to be checked and written manually on each HDR video.

If tagging for the source vid is unknown, find 1 of the following format in
source video metadata:

DCI-P3: G(x0.265, y0.690), B(x0.150, y0.060), R(x0.680, y0.320),
WP(x0.3127, y0.329)

bt.709: G(x0.30, y0.60), B(x0.150, y0.060), R(x0.640, y0.330),

bt.2020: G(x0.170, y0.797), B(x0.131, y0.046), R(x0.708, y0.292),

*Content lumiance x265: *--max-cll <max content light level cd/m2, max
frame-avg light level cd/m2> e.g., 1000,640

*Content lumiance x264: *--cll <max content light level cd/m2, max
frame-avg light level cd/m2> e.g., 1000,640

CLL has no standard and needs to be checked and written manually on each
HDR video

*Indicate HDR10 content in supplemential enhance info (SEI)**, x264 **: *

*Optimize HDR10 content (increase video size) per block (optional, x264
[image: :(] *--hdr10-opt

*Indicate color range and transfer properties: *--colormatrix <as source>
--transfer <as source>

Color range can vary thanks for both compatibility and multple HDR
implementations, (e.g., gbr bt709 fcc bt470bg smpte170m YCgCo bt2020nc
bt2020c smpte2085 ictcp). Check the source video metadata for them



this answer says mastering-display is NOT for your editing display but for
ideal viewing display! Are they supposed to be the same?

Not sure how you calculate max-cll et all from your display / source ...
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