I am trying to add two overlays using ffmpeg as below:

[v0][1:v] overlay=21:24:enable='between(t,0.000, 1.135)' [v1];
[v1][2:v] overlay=120:24:enable='between(t,0.000, 1.135)' " 

These two images [1:v] and [2:v] are below pngs:

enter image description here enter image description here

The first png is 99px wide and I want to place it on x=21

The second png I want to place right behind the first one x=21+99=120

But I am getting the output as below: It seems that there is 1px gap between them and I have no idea where is it coming from.

enter image description here

How can I ensure it is pixel perfect and there is no gap?

Also I noticed that if the image is 98px and I use:

[v0][1:v] overlay=21:24:enable='between(t,0.000, 1.135)' [v1];
[v1][2:v] overlay=119:24:enable='between(t,0.000, 1.135)' " 

then suprisingly it is fine, same for 100px wide and next images x=121

The whole command to give more context (remove newlines to execute):

.\bin\ffmpeg.exe -ss 0 -to 5.681 
-i C:\Users\Radoslaw\Videos\ttt.mp4 
-i .\tempAssets\player1.png 
-i .\tempAssets\serving.png 
[0:v] select='between(t,1.247,2.550)+between(t,4.181,5.681)', setpts='PTS-STARTPTS-((gt(T,2.550)*1.630))/TB' [v0]; 
[0:a] aselect='between(t,1.247,2.550)+between(t,4.181,5.681)', asetpts='PTS-STARTPTS-((gt(T,2.550)*1.630))/TB'; 
[v0][1:v] overlay=21:21:enable='between(t,0.000, 2.803)' [v1];
[v1][2:v] overlay=120:21:enable='between(t,0.000, 2.803)' 

@Gyan your answer helped for the mentioned simple scenario but if I change the order:

[v0][2:v] overlay=120:24:enable='between(t,0.000, 1.135)':format=auto,format=yuv444p [v1];
[v1][1:v] overlay=21:24:enable='between(t,0.000, 1.135)' " 

then I get the 1px gap again. Any suggestions?

  • 1
    Looks to be related to chroma subsampling of the base video. Share full command.
    – Gyan
    Feb 6, 2023 at 4:25
  • updated the question with the full command
    – RadekJ
    Feb 6, 2023 at 7:30

1 Answer 1


Change base video to full chroma sampling and try.

[0:v] select='between(t,1.247,2.550)+between(t,4.181,5.681)', setpts='PTS-STARTPTS-((gt(T,2.550)*1.630))/TB',format=yuv444p[v0];


[v0][1:v] overlay=21:21:enable='between(t,0.000, 2.803)':format=auto,format=yuv444p [v1];
[v1][2:v] overlay=120:21:enable='between(t,0.000, 2.803)'
  • Yes, that helped. Thanks a lot! Also after experimenting - turns out that it is enough to add :format=auto without specyfing the chroma sampling. Do you think it is enough to add :format=auto to each png overlay or should I add that chroma too?
    – RadekJ
    Feb 7, 2023 at 7:26
  • You shouldn't add auto format to the last overlay. The format after the first overlay may be removed.
    – Gyan
    Feb 7, 2023 at 7:35
  • hmm but if i change the order so [2:v] goes first and then [1:v] and put :format=auto,format=yuv444p on the first one (2:v) then the problem remains as before
    – RadekJ
    Feb 7, 2023 at 7:56

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