What is ffmpeg ? And how to resize your video ?

ffmpeg ¹⁾ is a command line to record, convert and stream audio and video.

This is the simple tool to manipulate and convert any video.

You can download it or install it via your package manager.

Example on linux ubuntu with apt

sudo apt install ffmpeg

To get information about your video, you would use the ffrpobe utility (installed with ffmped)

ffprobe video.mp4

Example of output where you can see the aspect ratio of 1920×1080

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    title           : Video Gifts
    artist          : Gerard nico
    encoder         : Lavf58.29.100
    keywords        : Video-Gifts
  Duration: 00:00:39.27, start: 0.000000, bitrate: 3067 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 2933 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
    Metadata:
      handler_name    : Core Media Video
      timecode        : 00:00:00;00
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
    Stream #0:2(eng): Data: none (tmcd / 0x64636D74)
    Metadata:
      handler_name    : Core Media Video
      timecode        : 00:00:00;00

The command is pretty simple

ffmpeg -i input.mp4 output.avi

The command may also add more information such as the codec

ffmpeg -i {in-video}.mov -vcodec h264 -acodec aac {out-video}.mp4

In this example, we show you how to preserve aspect ratio which is almost what you want.

Example:

• video

ffmpeg -i output.mp4 -vf scale=960:-1 output_960.mp4

• A image

ffmpeg -i input.jpg -vf scale=320:-1 output_320.png

• To encode a movie to frame (single pictures) sampled (every n frames) ²⁾

ffmpeg -i movie.mpg movie%d.jpg

• Extract the first 20 frames

ffmpeg -i input.mp4 -vframes 20 output_image_%03d.jpg

• To extract the 30 frame

ffmpeg -i input.mp4 -vf "select=eq(n\,30)" -vframes 1 output_image.jpg