am trying to cut a part of Video

Here is the code i have tried Let's say i have 6 seconds video and i want to slow down 2:5 seconds video that 3 second video

First approach after searching is, Cut the video, then apply slow filter then concat it with original video. But this is a mid part not entire video. How can i modify below code

ffmpeg -i Soon.mp4 -filter_complex [0:v]trim=2:5,setpts=PTS-STARTPTS[v1];[v1]setpts=0.5PTS[v1];[0:a]atempo=2[a] concat=n=1:v=1:a=1 -map "[v]" -map "[a] -preset superfast -profile:v baseline output.mp4

3 Answers 3


This slows down one part of a video and keeps the rest as is.

ffmpeg -i Soon.mp4
  -preset superfast -profile:v baseline output.mp4

How does it work?

  • The trim and atrim filters cut the video into different parts, from 0–2 seconds, from 2–5, and from 5 to the end.
  • In each part a setpts/asetpts filter is applied, which, when using the option PTS-STARTPTS, "resets" the presentation timestamps of each frame in each part, so that they can later be concatenated easily.
  • Each part is given an output label (e.g. [v1] through [v3]).
  • For the video parts that need to be slowed down, every presentation timestamp is doubled (2*(…)), which effectively halves the speed of the video. If you wanted to speed up the video, use a multiplier lower than 1.
  • For audio parts to be sped up / slowed down, use the atempo filter, whose parameter is the speedup (e.g., 0.5 = half speed).
  • These parts are finally concatenated using the concat filter.
  • Hi Thanks for this code :) can u please explain this part [0:a]atrim=2:5,asetpts=2*(PTS-STARTPTS),atempo=0.5[a2]; what is 2 and 0.5? Commented Jun 27, 2017 at 20:19
  • If you're slowing down part of a video, you'll want to slow down corresponding audio as well. But not the other parts of the audio. That 2 is not needed. Removed. 0.05 is to slow down the audio by 2.
    – Gyan
    Commented Jun 28, 2017 at 4:57
  • 1
    Note: -preset superfast -profile:v baseline will usually result in very bad quality and/or high file sizes. Unless you know that you need these options, it's better to not use them and let ffmpeg use the default settings.
    – slhck
    Commented Aug 18, 2019 at 15:46
  • Worked perfectly! Thanks so much. Commented Jul 11, 2020 at 16:11

Thanks to Gyan's answer! Taking that plus a bit research, I have applied it to speed up a video with audio by 6 times. Be aware that atempo argument has a value ranging between 0.5 and 2. So three atempo were used to make up 6 (2 x 2 x 1.5). So the idea is to make the video from 00:00:00 to 00:17:30, a total of 1050 seconds, to play 6 times faster and the rest stays unchanged. Code example as follows:

ffmpeg -i in_file.mp4 -filter_complex \
   [v1][a1][v2][a2]concat=n=2:v=1:a=1" \

@ slhck

This slows down one part of a video and keeps the rest as is.

I've never seen PTS-STARTPTS before. I have always used just PTS for this purpose. I have a recent script that hangs with just PTS but it works with PTS-STARTPTS. Can you explain why?

With PTS

ffmpeg -i "input.mkv" \
-filter_complex \
" \
[0:v]trim='00\:08\:23.961':'00\:08\:24.379',setpts=4*PTS,curves=psfile=curves40.acv,unsharp=13:13:1.5:13:13:1.5[v0]; \
[0:a]atrim='00\:08\:23.961':'00\:08\:24.379',asetpts=PTS,atempo=0.5,atempo=0.5[a0]; \
[0:v]trim='00\:08\:23.961':'00\:08\:24.379',reverse,setpts=4*PTS,curves=psfile=curves40.acv,unsharp=13:13:1.5:13:13:1.5[v1]; \
[0:a]atrim='00\:08\:23.961':'00\:08\:24.379',areverse,asetpts=PTS,atempo=0.5,atempo=0.5[a1]; \
[v0][a0][v1][a1]concat=n=2:v=1:a=1[out] \
" \
-map "[out]" \
-r $fps -c:v libx264 -preset slow -crf 10 -map_chapters -1 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 \
-movflags faststart "otput.mp4"


ffmpeg -i "input.mkv" \
-filter_complex \
" \
[0:v]trim='00\:08\:23.961':'00\:08\:24.379',setpts=4*(PTS-STARTPTS),curves=psfile=curves40.acv,unsharp=13:13:1.5:13:13:1.5[v0]; \
[0:a]atrim='00\:08\:23.961':'00\:08\:24.379',asetpts=PTS-STARTPTS,atempo=0.5,atempo=0.5[a0]; \
[0:v]trim='00\:08\:23.961':'00\:08\:24.379',reverse,setpts=4*(PTS-STARTPTS),curves=psfile=curves40.acv,unsharp=13:13:1.5:13:13:1.5[v1]; \
[0:a]atrim='00\:08\:23.961':'00\:08\:24.379',areverse,asetpts=PTS-STARTPTS,atempo=0.5,atempo=0.5[a1]; \
[v0][a0][v1][a1]concat=n=2:v=1:a=1[out] \
" \
-map "[out]" \
-r $fps -c:v libx264 -preset slow -crf 10 -map_chapters -1 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 \
-movflags faststart "otput.mp4"

In both cases I get frame= 0 fps=0.0 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A speed= 0x but it works in this case.

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