[FFmpeg-user] ffmpeg architecture question #2

[Carl Eugen Hoyos]

> Am 24.04.2020 um 19:34 schrieb pdr0 <pdr0 at shaw.ca>:
> 
> Carl Eugen Hoyos-2 wrote
>>> Am 24.04.2020 um 11:10 schrieb Mark Filipak <
> 
>> markfilipak.windows+ffmpeg@
> 
>> >:
>>> 
>>> I've been told that, for soft telecined video the decoder is fully
>>> compliant and therefore outputs 30fps
>> 
>> (“fps” is highly ambiguous in this sentence.)
>> 
>> This is not correct.
>> I believe I told you some time ago that this is not how the decoder
>> behaves. I believe such a behaviour would not make sense for FFmpeg
>> (because you cannot connect FFmpeg’s output to an NTSC CRT). The telecine
>> filter would not work at all if above were the case.
>> Or in other words: FFmpeg outputs approximately 24 frames per second for
>> typical soft-telecined program streams.
>> 
>> The only thing FFmpeg does to be “compliant” is to forward the correct
>> time base.
> 
> 
> If you use direct encode, no filters, no switches, the output from soft
> telecine input video is 29.97p, where every 5th frame is a duplicate

No

> e.g
> ffmpeg -i input.mpeg -c:v rawvideo -an output.yuv

(Consider to test with other output formats.)

> But you can "force" it to output 23.976p by using -vf fps
> 
> Is this what you mean by "forward the correct time base" ?

No.

Carl Eugen