[FFmpeg-user] rgb8

[Michael Koch]

Am 31.05.2023 um 09:16 schrieb Reindl Harald:
>
>
> Am 31.05.23 um 09:14 schrieb Michael Koch:
>> Am 31.05.2023 um 08:56 schrieb 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.
>>
>> Couldn't this be simplified with a new filter "set_pixel_format" 
>> which tells FFmpeg to interpret the data as a different pixel format, 
>> without making any modifications to the data?
>> In my case the data is already correct. It's only labeled incorrectly.
>
> "-pixel_format rgb8" as input parm tells ffmpeg exactly that

yes, but I can't use "-pixel_format gray" because the DirectShow driver 
accepts only those pixel formats that are listed with "ffmpeg 
-list_options 1 -f dshow -i video="ASI178MM Camera (ZWO Design)"
There is only one pixel format listed and that's "rgb8".

Michael