[FFmpeg-user] Decombing via screening - 'tblend' bug (?)

[Paul B Mahol]

On 4/15/20, Mark Filipak <markfilipak.windows+ffmpeg at gmail.com> wrote:
> Request for bug confirmation is included.
>
> Correction: I had datascope in #2 just 1 time. I don't know how it got into
> the original post twice.
> Sorry. - M.
>
> On 04/14/2020 10:24 AM, Paul B Mahol wrote:
>> On 4/14/20, Mark Filipak <markfilipak.windows+ffmpeg at gmail.com> wrote:
>>> In the command line below,
>>>                  I will eventually insert a screen maker --+
>>>                                                            ¦
>>> separatefields,scale=height=2*in_h:sws_flags=neighbor,--HERE--,tblend=normal[D]
>>>
>>> but first, I need to persuade 'tblend' to accept the 2 frames made by
>>> 'separatefields' (and scaled
>>> by 'scale').
>>> But as you can see in the next section (extracted from the log), though
>>> the
>>> 'height=2*in_h'
>>> directive works (i.e., the 1920x540 frames from 'separatefields' are
>>> scaled
>>> to 1920x1080), ffmpeg is
>>> not happy. Is it because the SARs don't match? How can I overcome that?
>>> Thanks!
>>
>> Insert setsar=1 after scale?
>
> Thank you, Paul. It works. I apologize for not finding that solution on my
> own ...how embarrassing.
>
> Next problem: 'tblend' appears to be malfunctioning.
>
> "The tblend (time blend) filter takes two consecutive frames from one single
> stream, and outputs the
> result obtained by blending the new frame on top of the old frame."
>
> #1 - This works as expected:
> ffmpeg -i IN -filter_complex "telecine=pattern=5, split[A][B],
> [A]select='not(eq(mod(n+1\,5)\,3))'[C], [B]select='eq(mod(n+1\,5)\,3)',
> datascope=size=1920x1080:x=45:y=340:mode=color2[D], [C][D]interleave" OUT
>
> #2 - This malfunctions:
> ffmpeg -i IN -filter_complex "telecine=pattern=5, split[A][B],
> [A]select='not(eq(mod(n+1\,5)\,3))'[C], [B]select='eq(mod(n+1\,5)\,3)',
> separatefields,
> scale=height=2*in_h:sws_flags=neighbor, setsar=1, tblend,
> datascope=size=1920x1080:x=45:y=340:mode=color2, [C][D]interleave" OUT
>
> #1 brings up datascope in frames (n, zero-based): 2 7 12 17 etc., as
> expected.
> #2 brings up datascope in frames (n, zero-based): 4 7 10 13 etc.
>
> Another clue is:
> #1 OUT has 598 frames.
> #2 OUT has 716 frames.
>
> Would someone who has the latest nightly build kindly confirm this. I can
> supply the test video --
> contact me off-list.

You still can not read documentation? Why?

interleave filter simply picks frames from several streams.
This is obviously explained in documentation.
tblend filter blend successive frames, this is obviously different
from interlace filter as that will not drop any frame like interlace
does.

>
> Thanks,
> Mark.
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