[FFmpeg-user] ffmpeg architecture question

[Michael Koch]

Am 17.04.2020 um 09:44 schrieb Mark Filipak:
> On 04/17/2020 02:41 AM, Michael Koch wrote:
>> 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]?
>
> This would be an important topic for someone writing a book, eh?
>
> I assume you mean this, Michael:
>
> 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]
>
> split[A]         0 1 _ 3 4         [C]interleave 0 1 _ 3 4  //4 frames
>      [B]split[D] _ _ 2 _ _ [F]blend[D]
>              [E] _ _ _ _ _ [G]
>

no, I meant replace [F][G]blend[D] by [G][F]blend[D] and leave 
everything else as it is.

Michael