[FFmpeg-user] ffmpeg architecture question #2

[Mark Filipak]

On 04/24/2020 01:28 PM, pdr0 wrote:
> Mark Filipak wrote
>>> I've been told that, for soft telecined video
>>>   the decoder is fully compliant and therefore outputs 30fps
>>> I've also been told that the 30fps is interlaced (which I found
>>> surprising)
>>> Is this correct so far?
> 
> Yes
> 
> If you take a soft telecine input, encode it directly to rawvideo or
> lossless output, you can confirm this.
> The output is 29.97 (interlaced content) .
> 
>> When I do 'telecine=pattern=5', I wind up with this
>>
>> |<--------------------------1/6s-------------------------->|
>> [A/a_][A/a_][A/b_][B/b_][B/b_][C/c_][C/c_][C/d_][D/d_][D/d_] 55-telecine
>>
>> I have confirmed it by single-frame stepping through test videos.
> 
> No.

The above timing is for an MKV of the 55-telecine transcode, not for the decoder's output.

> Pattern looks correct, but unless you are doing something differently , your
> timescale is not correct
> 
> When input is vob, mpeg2-ps or mpeg-es using soft telecine in my test, using
> telecine=pattern=5 the output frame rate is 74.925 as expected  (2.5 * 29.97
> = 74.925).

Not for me. I've seen 74.925 FPS just one time. Since I considered it a failure, I didn't save the 
video and its log, so I don't know how I got it.

> This mean RF flags are used, 29.97i output from decoder. Since
> its 74.925fps, the scale in your diagram for 1/6s is wrong for
> telecine=pattern=5

For this command line:

ffmpeg -report -i "00001.018.m2ts" -filter_complex 
"telecine=pattern=5,split=5[A][B][C][D][E],[A]select='eq(mod(n+1\,5)\,1)'[F],[B]select='eq(mod(n+1\,5)\,2)'[G],[C]select='eq(mod(n+1\,5)\,3)'[H],[D]select='eq(mod(n+1\,5)\,4)'[I],[E]select='eq(mod(n+1\,5)\,0)'[J],[F][G][H][I][J]interleave=nb_inputs=5" 
-map 0 -c:v libx264 -crf 20 -codec:a copy -codec:s copy "C:\AVOut\00001.018.4.MKV"

MPV playback of '00001.018.4.MKV' says "FPS: 59.940 (estimated)" (not 74.925fps).

> Both ffplay and mpv look like they ignore the repeat field flags, the
> preview is progressive 23.976p

I use MPV. I'm unsure what you mean by "preview". ...and "preview" of what? The decoder output or 
the MKV output video?