Am 08.11.2020 um 18:12 schrieb ZEITFELD:
Hello nice girls ans guys!
I have a highspeed camera that records raw data to DNG files. Now I try
to have the fastest possible preview video of what is recorded. I
succeeded using the GPU via FFMPEG, which is absolutely the fastest way
I found until now.
This is the command line I use:
FFMPEG -R 25 -F IMAGE2 -I FRAME_%06D.DNG -VCODEC LIBX264 -CRF 25
-PIX_FMT YUV420P PREVIEW.MP4
This gives me a MP4, but the colors are broken, the image is too dark
and green and the quality is very bad, with a lot of banding and
artifacts.
Does anyone know how to make ffmpeg apply reasonably balanced settings
when reading the DNGs?
did you (or anybody else) find a solution for this problem?
Paul did already give a few hints:
-- swscale is old and ignores color_trc metadata that is required for
correct display
-- use zscale for converting pixel formats
-- set output trc
-- make sure to set right pixel format prior to calling zscale as it
does not support bayer formats
Open questions:
-- How can zscale be used for converting the pixel format, if it doesn't
support the "bayer_rggb16le" format that the input images have? zscale
doesn't have any options for pixel formats.
-- Is "output trc" a synonym for "transfer characteristic"? Is that the
"transfer" option in zscale? To which value must it be set?
-- How can the pixel format be set prior to calling zscale? With
"-pix_fmt" before the input? Or after the input? Or with
"-pixel_format"? Or with "format=" at the beginning of the filter chain?
-- The input color space is "sRGB". How can this be set?
I did already spend about 20 hours of try-and-error on this problem
before I gave up.
Part of the problem is the missing documentation for the zscale filter.
That's only a list of options and possible values. No explanations what
the options mean, and no examples.
Michael
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