[FFmpeg-user] Directly converting DNGs to MP4

[Paul B Mahol]

On Sun, Nov 22, 2020 at 11:35 AM Michael Koch <astroelectronic at t-online.de>
wrote:

> 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?
>

There is a solution, but I gave up teaching unteachable.


>
> 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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