[FFmpeg-user] rgb8

Michael Koch astroelectronic at t-online.de
Wed May 31 09:27:50 EEST 2023

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.


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