[FFmpeg-user] ffmpeg architecture question

[Michael Koch]

Am 17.04.2020 um 08:02 schrieb Mark Filipak:
> Thanks to pdr0 -at- shaw.ca, My quest for the (nearly perfect) 
> p24-to-p60 transcode has concluded.
>
> But remaining is an ffmpeg behavior that seems (to me) to be key to 
> understanding ffmpeg architecture, to wit: The characteristics of 
> frame traversal through a filter chain.
>
> From a prior topic:
> -----
> Filter graph:
>
> split[A]    select='not(eq(mod(n+1\,5)\,3))'       [C]interleave
>      [B]split[D]select='eq(mod(n+1\,5)\,2)'[F]blend[D]
>              [E]select='eq(mod(n+1\,5)\,3)'[G]
>
> What I expected/hoped:
>
> split[A]         0 1 _ 3 4         [C]interleave 0 1 B 3 4  //5 frames
>      [B]split[D] _ 1 _ _ _ [F]blend[D]               |
>              [E] _ _ 2 _ _ [G]                       blend of 1+2
>
> What appears to be happening:
>
> split[A]         0 1 _ 3 4         [C]interleave 0 1 _ 3 4  //4 frames
>      [B]split[D] _ _ _ _ _ [F]blend[D]
>              [E] _ _ 2 _ _ [G]
>
> The behavior is as though because frame 1 (see Note) can take the 
> [A][C] path, it does take it & that leaves nothing left to also take 
> the [B][D][F] path, so blend never outputs.

Only an untested idea, what happens when you change the order of the 
inputs of the blend filter, first [G] and then [F]?

Michael