[FFmpeg-user] bwdif filter question

Mark Filipak (ffmpeg) markfilipak at bog.us
Wed Sep 23 23:26:27 EEST 2020

On 09/23/2020 03:53 PM, Carl Eugen Hoyos wrote:
> Am Di., 22. Sept. 2020 um 00:47 Uhr schrieb Mark Filipak (ffmpeg)
> <markfilipak at bog.us>:
>> On 09/21/2020 06:07 PM, Carl Eugen Hoyos wrote:
>>> Am Mo., 21. Sept. 2020 um 14:16 Uhr schrieb Mark Filipak (ffmpeg)
>>> <markfilipak at bog.us>:
>>>> Here is what you wrote:
>>>> "The following makes little sense, it is just meant as an example:
>>>> $ ffmpeg -f lavfi -i testsrc2,field -vf bwdif -f null -"
>>>> That "explains" nothing. Worse, it seems crass and sarcastic.
>>> No.
>>> This was an example to show you how you can feed one field to
>>> a filter in our system, this is what you had asked for ...
>> I didn't ask for that.
> This is not true:
>> How can a frame contain just one field?

I did not ask for an example to see "how you can feed one field to a filter". I asked how a frame 
can contain just one field. You have yet to answer that. I think it's impossible. You may be 
referring to a frame that is deinterlaced and cut in half (e.g. from 720x576 to 720x288), in which 
case the frame contains no field.

You wrote: "(If you provide only one field, no FFmpeg deinterlacer will produce useful output.)". Of 
course I agree with the "no...useful output" part, however, how can a person "provide only one 
field"? That implies that "provide only one field" is an option. I think that's impossible, so I 
asked you how it was possible. I did not ask how to implement that impossibility on the command line 
(which I think is likewise impossible). It is along these lines that misunderstanding and confusion 
and novice angst ensues.

Am I nitpicking? I think not. You are an authority. When an authority uses loose language, 
misunderstanding and confusion and angst must follow. But MPEG and ffmpeg seems to be primed to 
require loose language. That needs to end.

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