I would like to convert a high quality non interlaced input video into a less quality but wider distributable H.264/MP4 format. The output should have some constraints - in particular: it should be **interlaced**!

I tried the following command, where `mandelbrot` is a synonymous for the high quality input:

```
ffmpeg -hide_banner \
    -t 10 -y \
    -f lavfi \
    -i anullsrc=r=48k:cl=stereo \
    -f lavfi \
    -i mandelbrot=r=50:size=1920x1080 \
    -vf 'interlace=scan=tff:lowpass=complex,format=yuv420p' \
    -codec:a aac \
    -b:a 128k \
    -aac_coder twoloop \
    -codec:v libx264 \
    -preset veryfast \
    -tune animation \
    -profile:v high \
    -crf 35 \
    -level 5.2 \
    -x264opts interlaced=1 \
    -shortest \
    mandelbrot.mp4

```

My ffmpeg is `ffmpeg version 3.4.2-2`.

However, I am not sure that the command line is correct.

* `libx264` does not detect an interlaced input by itself. I have to insert `-x264opts interlaced=1`.
* Other faq's tell something about `-flags +ilme+ildct`...

Can you confirm my parameters? Thank you very much.