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custom_filters.md

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Custom filter

ffplayout allows the definition of a custom filter string. For this, the parameter custom_filter is available in the playout configuration under processing. The playlist can also contain a custom_filter parameter for each clip, with the same usage.

The filter outputs should end with [c_v_out] for video filters and [c_a_out] for audio filters. The filters will be applied to every clip and after the filters that unify the clips.

It is possible to apply only video filters, only audio filters, or both. For a better understanding, here are some examples:

Apply Gaussian blur and volume filter:

custom_filter: "gblur=5[c_v_out];volume=0.5[c_a_out]"

Apply loudnorm filter:

custom_filter: "loudnorm=I=-18:TP=-1.5:LRA=11[c_a_out]"

Dynamic Audio Normalizer | Compressor | Limiter

This filter should be used in preference to the loudnorm filter.

custom_filter: "dynaudnorm=f=200:g=15,acompressor=threshold=0.2:ratio=4:attack=20:release=250:knee=2.5,alimiter=level_in=1.0:limit=0.9:level_out=0.95:release=50[c_a_out]"

Add lower third:

custom_filter: "[v_in];movie=/path/to/lower_third.png:loop=0,scale=1024:576,setpts=N/(25*TB)[lower];[v_in][lower]overlay=0:0:shortest=1[c_v_out]"

Overlay current time:

custom_filter: "drawtext=text='%{localtime\:%H\\\:%M\\\:%S}':fontcolor=white:fontsize=40:x=w-tw-20:y=20:box=1:[email protected]:boxborderw=10[c_v_out]"

Scrolling text with static background:

custom_filter: "drawbox=x=0:y=in_h-(in_h/6):w=in_w:h=60:t=fill:color=#000000@0x73,drawtext=text='Hello World':x='ifnot(ld(1),st(1,t));if(lt(t,ld(1)+1),w+4,w-w/12*mod(t-ld(1),12*(w+tw)/w))':y='main_h-(main_h/6)+20':fontsize=24:fontcolor=#f2f2f2"

Pay attention to the filter prefix [v_in];, this is necessary to get the output from the regular filters.

Paint effect

custom_filter: "edgedetect=mode=colormix:high=0[c_v_out]"

Where the filters applied in stream mode

The custom filter from config -> processing and from playlist got applied in the decoder instance on every file:

flowchart LR

    subgraph fileloop["file loop"]
        direction LR
        Input --> dec
        subgraph filter["start new on file change"]
            direction LR
            dec["decoder / filtering / custom filter"]
            end
        end
    subgraph fileout["constant output"]
        direction LR
        enc["encoder / text overlay"]
    end
    dec -- PIPE --> enc
    enc --> output
Loading

When take which

  • If you want to use for every clip a different filter chain, you should use the custom filter parameter from playlist.
  • When you want to use the same filter for every clip you can use the custom filter from config -> processing.

Complex example

This example takes a image and a animated mov clip with alpha and overlays them two times on different positions in time:

custom_filter: "[v_in];movie=image_input.png:s=v,loop=loop=250.0:size=1:start=0,scale=1024:576,split=2[lower_1_out_1][lower_1_out_2];[lower_1_out_1]fifo,fade=in:duration=0.5:alpha=1,fade=out:start_time=9.5:duration=0.5:alpha=1,setpts=PTS+5.0/TB[fade_1];[v_in][fade_1]overlay=enable=between(t\,5.0\,15.0)[base_1];[lower_1_out_2]fifo,fade=in:duration=0.5:alpha=1,fade=out:start_time=9.5:duration=0.5:alpha=1,setpts=PTS+30.0/TB[fade_2];[base_1][fade_2]overlay=enable=between(t\,30.0\,40.0)[base_2];movie=animated_input.mov:s=v,scale=1024:576,split=2[lower_2_out_1][lower_2_out_2];[lower_2_out_1]fifo,setpts=PTS+20.0/TB[layer_1];[base_2][layer_1]overlay=repeatlast=0[base_3];[lower_2_out_2]fifo,setpts=PTS+50.0/TB[layer_2];[base_3][layer_2]overlay=repeatlast=0[c_v_out]"

And here are the explanation for each filter:

# get input from video
[v_in];

# load the image, loops it for 10 seconds (25 FPS * 10), scale it to the target resolution, splits it into two outputs
movie=image_input.png:s=v,loop=loop=250.0:size=1:start=0,scale=1024:576,split=2[lower_1_out_1][lower_1_out_2];

# take output one from image, fades it in for 0.5 seconds, fades it out for 0.5 seconds, shift the start time to 00:00:05 (5 seconds)
[lower_1_out_1]fifo,fade=in:duration=0.5:alpha=1,fade=out:start_time=9.5:duration=0.5:alpha=1,setpts=PTS+5.0/TB[fade_1];

# overlay first output on top of the video, between second 5 and 15
[v_in][fade_1]overlay=enable=between(t\,5.0\,15.0)[base_1];

# take output two from image, fades it in for 0.5 seconds, fades it out for 0.5 seconds, shift the start time to 00:00:30 (30 seconds)
[lower_1_out_2]fifo,fade=in:duration=0.5:alpha=1,fade=out:start_time=9.5:duration=0.5:alpha=1,setpts=PTS+30.0/TB[fade_2];

# overlay second output on top of output from last overlay, between second 30 and 40
[base_1][fade_2]overlay=enable=between(t\,30.0\,40.0)[base_2];

# load the animated clip with alpha, scale it to the target resolution, splits it into two outputs
movie=animated_input.mov:s=v,scale=1024:576,split=2[lower_2_out_1][lower_2_out_2];

# shift the start from first animated clip to second 20
[lower_2_out_1]fifo,setpts=PTS+20.0/TB[layer_1];

# overlay the shifted animation on top of the last image overlay
[base_2][layer_1]overlay=repeatlast=0[base_3];

# shift the start from second animated clip to second 50
[lower_2_out_2]fifo,setpts=PTS+50.0/TB[layer_2];

# overlay the second shifted animation on top of the last overlay
[base_3][layer_2]overlay=repeatlast=0[c_v_out]

Check ffmpeg filters documentation, and find out which other filters ffmpeg has and how to apply.