FFMPEG

Comprehensive guide: ffmpeg.org

Trim videos

ffmpeg  -i <input_video> -ss <hh:mm:ss.mmm> -to <hh:mm:ss.mmm> -c copy <output_video>

This trims the video from the time mentioned after -ss to -to. -c copy This is an option to trim via stream copy which prevents re-encoding. Do not use if the input type is different from the output type. You can also use -t rather than -to to specify the length of the trim rather than a timestamp.

Crop videos

ffmpeg -i in.mp4 -filter:v "crop=out_w:out_h:x:y" -c:a copy out.mp4

NOTE: DO not use -c:a copy if the output is not the same type as input. This is used to prevent re-encoding which is necessary in case of changing type.

Where the options are as follows:

• out_w is the width of the output rectangle
• out_h is the height of the output rectangle
• x and y specify the top left corner of the output rectangle

To crop the bottom right quarter:

ffmpeg -i in.mp4 -filter:v "crop=in_w/2:in_h/2:in_w/2:in_h/2" -c:a copy out.mp4

You can refer to the input image size with in_w and in_h as shown in this first example. The output width and height can also be used with out_w and out_h.

Crop 20 pixels from the top, and 20 from the bottom:

ffmpeg -i in.mp4 -filter:v "crop=in_w:in_h-40" -c:a copy out.mp4

The filter will automatically center the crop if x and y are omitted such as in this example.

Transform

ffmpeg -i <input_video> -vf <transformation>
vf is an alias -filter:v.

Options for transformation:

• hflip -> horizontally flip the video.
• vflip -> vertically flip the video
• transpose=x -> rotate a video.
  • 0 -> 90CounterClockwise and vertical flip.
  • 1 -> 90Clockwise.
  • 2 -> 90CounterClockwise.
  • 3 -> 90Clockwise and Vertical flip.

Note: This will re-encode the audio and video parts. You can use -c:a copy to copy the audio without touching it.

Previewing Videos

ffplay -i input -vf "crop=in_w:in_h-40"

Convert video to different types

ffmpeg -i <input.mp4> <output.gif>

Just using the file extensions for the input and output will automatically recognize the type and convert it.

Audio Controls

Extract Audio

ffmpeg -i <input.mp4> -f mp3 -ab 192000 -vn <output.mp3>

The -i option in the above command is simple: it is the path to the input file. The second option -f mp3 tells ffmpeg that the output is in mp3 format. The third option i.e -ab 192000 tells ffmpeg that we want the output to be encoded at 192Kbps and -vn tells ffmpeg that we dont want video. The last param is the name of the output file.