[FFmpeg-user] rgb8

[Paul B Mahol]

On Wed, May 31, 2023 at 8:28 AM Michael Koch <astroelectronic at t-online.de>
wrote:

> Am 31.05.2023 um 08:15 schrieb Kieran O Leary:
> > On Wed 31 May 2023 at 06:18, Michael Koch <astroelectronic at t-online.de>
> > wrote:
> >
> >> Am 30.05.2023 um 22:53 schrieb Paul B Mahol:
> >>> On Tue, May 30, 2023 at 8:32 PM Michael Koch <
> >> astroelectronic at t-online.de>
> >>> wrote:
> >>>
> >>>> Am 30.05.2023 um 20:28 schrieb Reindl Harald:
> >>>>> Am 30.05.23 um 20:21 schrieb Michael Koch:
> >>>>>> ffmpeg -f dshow -video_size 1280x800 -framerate 5 -pixel_format rgb8
> >>>>>> -i video="ASI178MM Camera (ZWO Design)" -f rawvideo -frames 1 -y
> >>>>>> test.raw
> >>>>>>
> >>>>>> Then I did read this file, assuming that the pixel format is gray:
> >>>>>>
> >>>>>> ffmpeg -s 1280x800 -pixel_format gray -f rawvideo -i test.raw -y
> >>>>>> gray.png
> >>>>>>
> >>>>>> The result looks correct. Is it possible to do this in one command
> >>>>>> line? I mean just tell FFmpeg that the pixel format isn't rgb8 but
> >>>>>> gray, without making any modifications to the data?
> >>>>> parameters before the input file are *input params*
> >>>>>
> >>>>> so why don't you change "-pixel_format rgb8" to "-pixel_format gray"
> >>>>> in the first command line when you say it works in the second one?
> >>>> When reading from the camera, the pixel format must be rgb8 because
> this
> >>>> is the only format supported by the DirectShow driver. All other pixel
> >>>> formats give error message.
> >>>>
> >>> Yes, looks like buggy code, the rgb8 is actually gray and not color.
> >> Is it possible to get correct gray data from the buggy driver in one
> >> FFmpeg command line? I mean the data can only be read from the driver as
> >> rgb8. Is it possible to tell FFmpeg that it's actually gray? It works as
> >> a two-step process with an intermediate raw file, but I'd like to do the
> >> same thing in one command line in realtime.
> >
> >
> > I’m not as familiar with this kind of usage but does adding “-pix_fmt
> gray
> > “ as an output option not work for you?
>
> Then FFmpeg does convert from rgb8 to gray, which gives wrong noisy
> output. Because the data is already gray. It's only incorrectly labeled
> as rgb8.
>
>
Once I push extractplanes commit you will be able to extract r/g/b
component from rgb8.
And after that is just matter of using mergeplanes and geq filters.


> Michael
>
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