FFMpeg Notes

FFMpeg is a really cool command line utility for converting videos

ffmpeg -i input [options] output

Codec options

-acodec (-c:a)

• aac

-vcodec (-c:v)

• h264
• libx265
• copy (skip encoding, i.e for rotating or muting video)

Common Options:

-ss [start timestamp] -t [duration] -an (no audio) -vf [filter], -filter:v

Using CRF with H264/265 encoding:

-crf (constant rate factor) -crf 24 (lower quality) -crf 15 (higher quality)

Cut frame x/y in half to save storage

-vf scale=iw/2:ih/2

• 1080p becomes 960x540
• 720p becomes 640x360

Scale video

-vf scale=1280:720

https://trac.ffmpeg.org/wiki/Scaling:

“If you need to simply resize your video to a specific size (e.g 320 x 240), you can use the scale filter in its most basic form:

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

Speed up video for time lapse

Either drop every Xth frame, or change the frame rate of the video, or both. Dropping frames (changing PTS values) will NOT change the audio, so either mute it with -an, or speed it up to match the video with the atempo filter.

To double the speed of the video while keeping the same framerate, you can use:

ffmpeg -i input.mkv -filter:v "setpts=0.5*PTS" -an output.mkv (`setpts=0.5*PTS` will drop every other frame)

Drop every other frame and also double frame rate from 1080p30 video (4x speed, 60fps)

ffmpeg -i GOPRXXXX.MP4 -r 60 -filter:v setpts=0.25*PTS -an timelapse.mp4

https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video

Generate time lapse from sets of images

With a directory structure like this on a GoPro:

119GOPRO/
120GOPRO/
121GOPRO/
122GOPRO/
...

Use this to stitch them together, set fps to 60, and set the CRF to 30:

ffmpeg -i "%*GOPRO/%*.JPG" -r 60 -crf 30 output.mkv

Stabilize video (or time lapse!)

• Easy fast version:

    ffmpeg -i input.mov -vf deshake output.mov
  

• Harder (better) slower stronger version:

    ffmpeg -i timelapse.mp4 -vf vidstabdetect=stepsize=32:shakiness=10:accuracy=10:result=transform_vectors.trf -f null -
  
    ffmpeg -i input.mp4 -vf vidstabtransform=input=transform_vectors.trf:zoom=0:smoothing=10,unsharp=5:5:0.8:3:3:0.4 -vcodec libx264 -tune film -an stabilized.mp4
  

https://www.imakewebsites.ca/posts/2018/02/17/stabilizing-gopro-video-with-ffmpeg-and-vid.stab/

Video compression for GoPro 1080p30 and 720p60

ffmpeg -i GOPRXXXX.MP4 -crf 35 -vf "scale=iw/2:ih/2" -filter:v fps=fps=24 -vcodec libx265 compressed.mp4

Hardware encoding

ffmpeg -i input.mkv -vaapi_device /dev/dri/renderD128 -vf "format=nv12,hwupload" -c:v h264_vaapi output.mkv

Motion interpolation

ffmpeg -i input.mkv -filter:v "minterpolate='mi_mode=mci:mc_mode=aobmc:vsbmc=1:fps=240'" output.mkv

…and then change the frame rate to 30fps (30/240 = 1/8 speed)

ffmpeg -i output.mkv -r 30 slow.mkv

Stack videos vertically or horizontally

ffmpeg -i a.mp4 -i b.mp4 -filter_complex vstack merged.mp4
ffmpeg -i a.mp4 -i b.mp4 -filter_complex hstack merged.mp4

August 5, 2019

Galen Asphaug