FFMPEG: using video filter with complex filter

Question

I'm using the fluent-ffmpeg Node.js library to perform batch manipulations on video files. The video filter which crops a 16:9 input, adds padding and burns subtitles into the padding.

In the next step, I would like to use a complex filter to overlay an image as a watermark.

ff.input(video.mp4)
ff.input(watermark.png)
ff.videoFilter([
  'crop=in_w-2*150:in_h',
  'pad=980:980:x=0:y=0:color=black',
  'subtitles=subtitles.ass'
])
ff.complexFilter([
  'overlay=0:0'
])
ff.output(output.mp4)

However, running this, I get the following error:

Filtergraph 'crop=in_w-2*150:in_h,pad=980:980:x=0:y=0:color=black,subtitles=subtitles.ass' was specified through the -vf/-af/-filter option for output stream 0:0, which is fed from a comple.
-vf/-af/-filter and -filter_complex cannot be used together for the same stream.

From what I understand the video filter and complex filter options can't be used together. How does one get around this?

Answer 1

Solved this by learning some basics about filter graphs. Here's the full ffmpeg command. I find the filter strings easier to read when they are written out line-by-line.

ffmpeg \
-i video.mp4 \
-i watermark.png \
-filter_complex " \
  [0]crop = \
    w = in_w-2*150 : \
    h = in_h \
    [a] ;
  [a]pad = \
    width = 980 : \
    height = 980 : \
    x = 0 :
    y = 0 :
    color = black
    [b] ;
  [b]subtitles = 
    filename = subtitles.ass
    [c] ;
  [c][1]overlay = \
    x = 0 :
    y = 0
  " \
output.mp4

Explanation:

[0]crop=...[a]; => Begin by applying crop filter to video input 0. Name the result a.

[a]pad=...[b]; => Apply the pad filter to the a stream. Name the result b.

[b]subtitles=...[c] => Apply the subtitles filter to the b stream. Name the result c.

[c][1]overlay... => Apply the overlay filter to stream c using input 1 (the png file).

Hope this helps someone struggling with filter graphs.