Using ffmpeg to cut up video

Question

I am using ffmpeg to cut out a section of a large file like this:

ffmpeg -i input.wmv -ss 60 -t 60 -acodec copy -vcodec copy output.wmv

The -ss part works fine but the -t is ignored. It correctly removes the initial specified seconds specified with -ss but then keeps going to the end of the input with the copy.

Is there a way to use ffmpeg to cut off the end of a video without recoding it?

Answer 1

You can use the -ss option to specify a start timestamp, and the -t option to specify the encoding duration. The timestamps need to be in HH:MM:SS.xxx format or in seconds (s.msec).

The following would clip the first 30 seconds, and then clip everything that is 10 seconds after that:

ffmpeg -ss 00:00:30.0 -i input.wmv -c copy -t 00:00:10.0 output.wmv
ffmpeg -ss 30 -i input.wmv -c copy -t 10 output.wmv

Note that -t is an output option and always needs to be specified after -i.

Some tips:

• For older ffmpeg versions, if you use -ss after -i, you get more accurate seeking at the expense of a slower execution altogether. See also: Seeking with FFmpeg

• You can use -to instead of -t to specify the timestamp to which you want to cut. So, instead of -i <input> -ss 30 -t 10 you could also do -i <input> -ss 30 -to 40 to achieve the same thing.

• If your ffmpeg does not support -c, or -to, it is likely very outdated. Compile a new version yourself or download a static build from their homepage. It's really not complicated.

Answer 2

As other people mentioned, putting -ss before (much faster) or after (more accurate) the -i makes a big difference. The section "Fast And Accurate Seeking" on the ffmpeg seek page tells you how to get both, and I have used it, and it makes a big difference. Basically you put -ss before AND after the -i, just make sure to leave enough time before where you want to start cutting to have another key frame. Example: If you want to make a 1-minute clip, from 9min0sec to 10min 0sec in Video.mp4, you could do it both quickly and accurately using:

ffmpeg -ss 00:08:00 -i Video.mp4 -ss 00:01:00 -t 00:01:00 -c copy VideoClip.mp4

The first -ss seeks fast to (approximately) 8min0sec, and then the second -ss seeks accurately to 9min0sec, and the -t 00:01:00 takes out a 1min0sec clip.

Also note this important point from that page: "If you use -ss with -c:v copy, the resulting bitstream might end up being choppy, not playable, or out of sync with the audio stream, since ffmpeg is forced to only use/split on i-frames."

This means you need to re-encode the video, even if you want to just copy it, or risk it being choppy and out of sync. You could try just -c copy first, but if the video sucks you'll need to re-do it.

Answer 3

I found that -ss combined with -c copy resulted in a half-second chop at the start.

To avoid that, you have to remove the -c copy (which admittedly will do a transcode).

Answer 4

MANUALLY

Open the file in a media player that will frame by frame advance and play an AVISynth file with data such as:

DirectShowSource(("C:\Downloads\Video\Do you want him.flv"), Pixel_Type="yuy2").Crop(0,0,-0,-0)
Subtitle("C:\Downloads\Video\Do you want him.flv", font="Arial", size=24, text_color=$ff0000, align=3)
ShowFrameNumber(scroll=true, x=336, y=27, font="Arial", size=24, text_color=$ff0000)
ShowTime(x=398, y=44, font="Arial", size=24, text_color=$ff0000)

Then cut with the EXACT time format:

ffmpeg -i "Path\do you want him.flv"        \
       -ss 00:00:05.240 -to 00:00:08.360    \
       -vcodec libx264 -acodec libvo_aacenc \
       "Path\Do you want him1.flv"

and

ffmpeg -i "Path\do you want him.flv"        \
       -ss 00:00:10.240 -to 00:00:14.360    \
       -vcodec libx264 -acodec libvo_aacenc \
       "Path\Do you want him2.flv"

Now make a txt file with the video files with contents like:

file 'C:\Downloads\Video\Do you want him1.flv'
file 'C:\Downloads\Video\Do you want him2.flv'

Run ffmpeg:

ffmpeg -f concat -i FileList.txt -c copy "Path\NewName_joined.flv"

Answer 5

For me -t option didn't work, but -vframes worked. I prefer using #frames, since I would rather cut at I-Frames and I found out GOP for video using ffprobe.

The command line that worked for me is:

ffmpeg -ss 60s -i input.wmv -vframes 1800 -acodec copy -vcodec copy output.wmv

By the way, putting -ss in the front of -i makes a big difference in execution time.

Answer 6

As with user225366, the -t option doesn't work for short videos, but it does for longer videos. For short videos it seems that -frames:v is better. This is what worked for me.

ffmpeg -ss 4 -i input.mp4 -frames:v 200 -vcodec copy output.mp4

-acodec copy needs to added if the video has audio, as the other answers show.

Answer 7

I see not many mention this (I'm no expert so maybe there is a catch), but if your file has other streams like subtitles and other metadata like chapters and so on, it's possible to cut/trim and keep all streams with the following command

ffmpeg -to 60 -i input.mkv -map 0 -c copy output.mkv

With -map 0 you take all the streams in the file, and with -c copy you copy all them as they are.
Using -to omitting the start via -ss will cut the input video from start to second 60.

Fiddling with map is useful also if you want only specific streams to be kept in the cut (maybe you don't need all the audio sources in the file, or only some subtitles).

I use this when I need to split big MKV files that can't be stored in FAT32 storage.

Answer 8

use this format:

ffmpeg <start time> <input file> <cut duration> <out file>

eg. cut 60 second clip after 1 minute of video

ffmpeg.exe -ss 00:01:00 -i "in file.mp4" -to 00:01:00 -c copy out.mp4