[FFmpeg-user] simple bob -- How?

[Mark Filipak (ffmpeg)]

On 12/29/2020 04:39 AM, Paul B Mahol wrote:
> On Tue, Dec 29, 2020 at 10:32 AM Mark Filipak (ffmpeg) <markfilipak at bog.us>
> wrote:
> 
>> On 12/29/2020 04:09 AM, Mark Filipak (ffmpeg) wrote:
>>> On 12/29/2020 04:04 AM, Paul B Mahol wrote:
>>>> On Tue, Dec 29, 2020 at 9:56 AM Mark Filipak (ffmpeg) <
>> markfilipak at bog.us>
>>>> wrote:
>>>>
>>>>> On 12/29/2020 03:41 AM, Paul B Mahol wrote:
>>>>>> On Tue, Dec 29, 2020 at 5:51 AM Mark Filipak (ffmpeg) <
>>>>> markfilipak at bog.us>
>>>>>> wrote:
>>>>>>
>>>>>>> I seek a way to do simple bob (i.e. repeat fields at 2xFPS) with no
>>>>> other
>>>>>>> filtering. Can you help me?
>> -snip-
>>>>>> After so much time you still struggle a lot, buy some GUI tools and be
>>>>>> happy ever after.
>>
>> Here's what I've tried so far:
>> -filter_complex
>> "split[a][b],[a]separatefields[c],[b]separatefields[d],[c][d]join"
>> -filter_complex
>> "split[a][b],[a]separatefields[c],[b]separatefields[d],[c][d]interleave"
>> -vf "separatefields,shuffleframes=0 0,weave"
>> -vf separatefields,scale=720x480
>> -vf separatefields,scale=w=iw:h=2*ih
>> -filter_complex "split[a][b],[a]separatefields[c],[c][b]scale2ref"
>>
> 
> Do you want interlacer or deinterlacer? It is very unclear from your
> subject what you need.
> 
> Simple bob deinterlacer takes every single field and than interpolates
> missing fields with bilinear interpolation iirc.

I think that bob just separates fields (e.g. [720x480] -> [720x240][720x240]), then line doubles 
(e.g. [720x240][720x240] -> [720x480][720x480]). When it is played back, horizontal lines in the 
video appear to bob up and down (but at 60Hz, that's not very noticeable).