I have a lot of videos that are either 720x1280 or 1280x720. I want to convert all of them to 1280x720, but for the ones that are portrait I would like to show the full video with the remaining space to the left and right being a darkened, blurred version of the video.

I think this is pretty close to that, but it seems to go on forever (maybe because the color keeps providing frames?)

ffmpeg -i video.mp4 -lavfi "\
    [email protected]:size=720x405[dark];
    [bg][fg]overlay=(W-w)/2:(H-h)/2" \
    -vb 800K video_out.mp4

You can see that it just starts adding duplicate frames after it hits the end of the video (in the logging below the video is ~24 sec):

Stream mapping:
  Stream #0:0 (h264) -> crop (graph 0)
  Stream #0:0 (h264) -> scale (graph 0)
  overlay (graph 0) -> Stream #0:0 (libx264)
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Past duration 0.999992 too large    2256kB time=00:00:24.33 bitrate= 759.4kbits/s dup=1 drop=0 speed=1.36x
Past duration 0.799995 too large
frame= 3177 fps=101 q=-1.0 Lsize=    3797kB time=00:01:45.80 bitrate= 294.0kbits/s dup=407 drop=0 speed=3.37x

How do I fix the issue of the encoding not completing when the end of the video file is reached?

Also, is there a way to conditionally only do the blurred background work if the video is portrait so landscape videos don't spend a lot of unnecessary CPU on blurring the video?

  • 3
    Just a suggestion: Instead of a target bitrate (-vb 800k), use a target quality value, e.g. -crf 18, or two-pass encoding. This will provide an overall better quality / bitrate efficiency. See trac.ffmpeg.org/wiki/Encode/H.264
    – slhck
    Jul 2, 2017 at 7:48
  • @slhck Thank you! I'll change that, appreciate it!
    – Blixt
    Jul 3, 2017 at 3:00

1 Answer 1


Limit the color output to a few frames. In the first overlay, it will repeat the last frame of the color once that stream ends. So, [email protected]:size=720x405:d=1[dark];

Filters can't be executed conditionally, so you will need to probe the input in a separate command beforehand and then execute a command with the filters or one without.

The command below

ffprobe in.mp4 -show_entries stream=display_aspect_ratio -of compact=p=0:nk=1 -v 0

will produce an output like this:


Just wrap a script to check that value.

  • 1
    Thanks! For me, since my video was from Zoom Cloud Recordings and had black bars on the sides, I first needed to crop it to actual portrait mode with ffmpeg -i input.mp4 -vf "crop=270:360" portrait_cropped.mp4 and then ran ffmpeg -i portrait_cropped.mp4 -lavfi "[email protected]:size=270x360:d=1[dark];[0:v]crop=270:360[blurbase]; [blurbase]boxblur=luma_radius='min(h,w)/20':luma_power=1:chroma_radius='min(cw,ch)/20':chroma_power=1[blurred]; [blurred][dark]overlay[darkened]; [darkened]scale=640:360[bg]; [0:v]scale=-1:360[fg]; [bg][fg]overlay=(W-w)/2:(H-h)/2" with_dark_blur.mp4
    – Ryan
    Feb 1, 2018 at 0:18

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