FFmpeg – tips and tricks

Over the years, and in particular with preparing videos of a conference for publication on YouTube, I have accumulated a few reminders how to do things with FFmpeg. It is such a fantastic beast full of features, that I will never run out of new things to learn.
(Update 2022-11-30: Found that excellent lengthy intro: FFmpeg – The Ultimate Guide)

So here we go, in some rather random order:

split at time stamps

Basic usage:

ffmpeg -i INPUT -ss STARTTS -to ENDTS -c copy OUTFILE

WARNING: since splitting is only possible at keyframes, this will by default set an “editlist” and start at the previous keyframe, and tell the player to start playing after the required difference.

Now that is a pain, because watermarking (see below) requires
--ignore_editlist 1
and then the audio gets out of sync!!!!

In this case one need to do the splitting already in addition to recoding and resizing so that it splits at the exact time!!!

concat two mp4 files

ffmpeg -i input1.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts
ffmpeg -i input2.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate2.ts
ffmpeg -i "concat:intermediate1.ts|intermediate2.ts" -c copy -bsf:a aac_adtstoasc output.mp4

see Concatenation of files with same codecs, at concat protcocol

cut out a part from STARTCUT – ENDCUT

This is done by creating two intermediate files by rendering only the initial or end part and at the same time encoding to mpeg-2 transport streams:

ffmpeg -i INPUT -ss 00:00:00 -to STARTCUT -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts
ffmpeg -i INPUT -ss ENDCUT -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts
ffmpeg -i "concat:intermediate1.ts|intermediate2.ts" -c copy -bsf:a aac_adtstoasc output.mp4

concat different formats

ffmpeg -i file1.mp4 -i file2.mp4 -i file3.mp4 \
  -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0][2:v:0][2:a:0]concat=n=3:v=1:a=1[outv][outa]"	\
  -map "[outv]" -map "[outa]" output.mp4

see here.

watermark

ffmpeg -i INPUT.mp4 -i TUG-33.png -filter_complex "overlay=x=(main_w-overlay_w-30):y=(main_h-overlay_h-30)" OUTPUT.mp4

If there is an error like

Could not find codec parameters for stream 0 ...
unspecified pixel format

one needs to add -ignore_editlist 1 which in turn requires proper cutting, see above.

(if necessary, add -analyzeduration 100M -probesize 100M)

simple scaling

ffmpeg -i input.avi -vf scale=320:240 output.avi

scale and watermark

ffmpeg -ignore_editlist 1 -i INPUT -i TUG-33.png -filter_complex "[0:v]scale=1920:1080 [mnn], [mnn][1:v]overlay=x=(main_w-overlay_w-30):y=(main_h-overlay_h-30)" OUTPUT

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 -ss 30 -t 10 you could also do -i -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.

still image (screenshot) from video

Trivial solution would be

ffmpeg -y -ss 00:$i -i $INPUT -frames:v 1 -q:v 2 ${OUTPUT}.jpg

but that does not keep aspect ratio (DAR Display Aspect Ratio). To get correct output:

ffmpeg -y -ss 00:$i -i $INPUT -vf scale='trunc(ih*dar):ih',setsar=1/1 -frames:v 1 -q:v 2 ${OUTPUT}.jpg