ffmpeg-imagemagick.md

Combine a folder of .m4a files into a single .m4a

folder="$1"

tmp_file='/Users/xiuming/Desktop/tmp.aac'
out_file='/Users/xiuming/Desktop/combined.m4a'

for f in "$folder"/*.m4a; do
    aac_file="$f.aac"
    ffmpeg -i "$f" -acodec copy "$aac_file" -y
    cat "$aac_file" >> "$tmp_file"
done

ffmpeg -i "$tmp_file" -bsf:a aac_adtstoasc "$out_file" -y

Resize video to 720p

ffmpeg -i nlt_v21.mp4 -vf scale=-1:720 -c:v libx264 -crf 18 -preset veryslow -c:a copy nlt_v21_720p.mp4

Cut video

ffmpeg -i input.mkv -ss 1:40:00.0 -c copy -to 1:59:15.30 output.mkv

• To also remove sound and convert format

   ffmpeg -i sintel.avi -ss 0:9:37.0 -c copy -to 0:9:40.50 -an bigFight.mp4

Change Frame Rate

• Speed up by 2x

  ffmpeg -i input.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mp4

Scale image

• Specify width

   ffmpeg -i in.png -vf scale=iw/2:-1 out.png

• Specify height

   ffmpeg -i in.png -vf scale=-1:ih/2 out.png

Convert format

ffmpeg -i dense.avi -c:v libx264 noDepth.mp4

Reverse video

ffmpeg -i video.mp4 -vf reverse video_rev.mp4

Concatenate videos

ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v] [1:v] concat=n=2:v=1 [v]" -map "[v]" video_concat.mp4

Change FPS

ffmpeg -i video.mp4 -filter:v "setpts=0.5*PTS" video_2xfps.mp4

Images to video

• Numeric filename

   ffmpeg -framerate 20 -start_number 1 -i %3d_0zz.png -vf fps=20 -pix_fmt yuv420p output.mp4

• Character filename

   ffmpeg -framerate 2 -pattern_type glob -i "*.png" -pix_fmt yuv420p output.mp4

• Filename of certain length

   ffmpeg -framerate 2 -pattern_type glob -i "???.png" -pix_fmt yuv420p -y output.mp4

  ???.png matches with all filenames of length 3. -y overwrites without asking.

• If not divisible by 2 (specify height)

   ffmpeg -framerate 10 -pattern_type glob -i "*.png" -vf scale=-2:720 -pix_fmt yuv420p output.mp4

• If not divisible by 2 (specify width)

   ffmpeg -framerate 10 -pattern_type glob -i "*.png" -vf scale=1280:-2 -pix_fmt yuv420p output.mp4

• Start from and end at

   ffmpeg -start_number 250 -i img_%4d.jpg -vframes 500 -vcodec mpeg4 output.mp4

  combines img_0250.jpg through img_0750.jpg.

• If high quality is required

  Set bitrate (around 5 Mbits/s for DVD) and codec by adding flags:

   -b 5000k -vcodec libx264

  If no H.264 support, use -vcodec mpeg4.

Make GIF

convert -delay 20 -loop 0 *jpg animated.gif

Crop GIF

convert in.gif -coalesce -repage 0x0 -crop WxH+X+Y +repage out.gif

Make GIF loop

convert -delay 20 -loop 0 nonloopingImage.gif loopingImage.gif

Overlay A on top of B

ffmpeg -i B.png -i A.png -filter_complex "[0:v][1:v] overlay" out.png

[0:v][1:v] means that we want the first video or image file we import with -i to be under the second video or image file.

• Scale A before overlaying

   ffmpeg -i B.png -i A.png -filter_complex "[1]scale=iw/2:-1[b];[0:v][b] overlay" out.png

  [1] is short for "pick the best matching stream" ([1:v] is short for pick the best matching video stream -- same thing in this case) and [b] is the label for the scale output which is then fed to the overlay.

• Make transparent A before overlaying

   ffmpeg -i B.png -i A.png -filter_complex "[1]format=argb,geq=r='r(X,Y)':a='0.5*alpha(X,Y)'[b];[0:v][b] overlay" out.png

  0.5 is the opacity factor. I'm including format=argb so that it also works with overlay images that don't have an alpha channel of themselves.

Horizontally stack two images/videos

ffmpeg -i a.jpg -i b.jpg -filter_complex hstack output

Horizontally stack two images/videos; need to rescale one

ffmpeg -i left.png -i right.png -filter_complex '[1][0]scale2ref=ih*(W/H):ih[2nd][ref];[ref][2nd]hstack' out.png

where H and W should be replaced with the height and width of right.png, respectively.

If calling this from Python, you may need to remove the quotes.

Vertically stack two images/videos; need to rescale one

ffmpeg -i top.png -i bottom.png -filter_complex '[1][0]scale2ref=iw:iw*(H/W)[2nd][ref];[ref][2nd]vstack' out.png

where H and W should be replaced with the height and width of bottom.png, respectively.

Overlay text on image

convert in.png -pointsize 40 -fill red -annotate +100+100 'My Text' out.png

Rotate images in a folder

for file in ./*.png; do
    convert "$file" -rotate 90 "${file%.png}"_rotated.png
done

Crop a video

ffmpeg -i gump_orig.mp4 -vf "crop=<out_w>:<out_h>:<x>:<y>" gump.mp4

Crop an image

ffmpeg -i in.png -vf "crop=<out_w>:<out_h>:<x>:<y>" out.png

Get image info

identify -verbose im.tif

Photo montage

montage [0-5].png -tile 5x1 -geometry +0+0 out.png

ImageMagick ships with the montage utility. Montage will append each image side-by-side allowing you to adjust spacing between each image (-geometry), and the general layout (-tile).

Replace alpha/transparent background with solid color

convert image.png -background white -alpha remove white.png

Change video speed

ffmpeg -i input.mkv -filter:v "setpts=PTS/60" output.mkv 

speeds up the video by 60x.

Replace image alpha background with a pure color

ffmpeg -i in.png -filter_complex "color=black,format=rgb24[c];[c][0]scale2ref[c][i];[c][i]overlay=format=auto:shortest=1,setsar=1" out.png

overlays the image with alpha on top of a black canvas.

Extract audio from video

ffmpeg -i input-video.avi -vn -acodec copy output-audio.aac

Replace audio in video

ffmpeg -i v.mp4 -i a.wav -c:v copy -map 0:v:0 -map 1:a:0 new.mp4

-map 0:v:0 maps the first (index 0) video stream from the input to the first (index 0) video stream in the output. -map 1:a:0 maps the second (index 1) audio stream from the input to the first (index 0) audio stream in the output.

.webm to .mp4, with high quality

ffmpeg -i video.webm -crf 1 -c:v libx264 video.mp4