[FFmpeg-user] fftfilt

[Michael Koch]

Am 14.10.2021 um 13:23 schrieb Paul B Mahol:
> On Thu, Oct 14, 2021 at 1:18 PM Michael Koch <astroelectronic at t-online.de>
> wrote:
>
>> Am 14.10.2021 um 13:11 schrieb Paul B Mahol:
>>> On Thu, Oct 14, 2021 at 1:08 PM Michael Koch <
>> astroelectronic at t-online.de>
>>> wrote:
>>>
>>>> Am 14.10.2021 um 13:01 schrieb Paul B Mahol:
>>>>> On Thu, Oct 14, 2021 at 12:59 PM Michael Koch <
>>>> astroelectronic at t-online.de>
>>>>> wrote:
>>>>>
>>>>>> Am 14.10.2021 um 12:53 schrieb Paul B Mahol:
>>>>>>> On Thu, Oct 14, 2021 at 12:29 PM Michael Koch <
>>>>>> astroelectronic at t-online.de>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Am 14.10.2021 um 12:07 schrieb Paul B Mahol:
>>>>>>>>> Sorry but I'm not on windows, so I can not use your script.
>>>>>>>> Then try the below (slightly improved) version. It would become much
>>>>>>>> simpler with variables:
>>>>>>>> ARRAY_H = pow(2,ceil(log(ceil(W*10/9))/log(2)))
>>>>>>>> ARRAY_V = pow(2,ceil(log(ceil(H*10/9))/log(2)))
>>>>>>>>
>>>>>>>> The test image contains wavelengths from 4 to 8 (in the center) to
>> 16
>>>>>>>> pixels per linepair.
>>>>>>>> The filter wavelength is independant of input size. You can change
>> the
>>>>>>>> size in the first command (but it must be 1:1 aspect ratio,
>> otherwise
>>>>>>>> hstack would fail)
>>>>>>>>
>>>>>>> Since when hstack fails because of different aspect ratio?
>>>>>> Because I first make the left half of the test image, then transpose
>> it
>>>>>> and then hstack them together
>>>>>>
>>>>>> The fftfilt examples do of course work with any aspect ratio.
>>>>>>
>>>>> I think you do not understand what aspect ratio really means.
>>>> width / height
>>>>
>>> Doesn't all this introduces aliasing if not using power of 2 width and
>>> height square dimensions?
>> I'm not sure if I understand what you mean. Do you see a significant
>> difference if you make the input size 250x250 or 256x256?
>>
>
> it did for first test.png  you sent

The first version was with square waves. It's better to test with the 
last version which uses sine waves and the wavelength changes continuously.

Michael