FFmpeg: changing aspect ratio

Posted on: 05 Jun 2024

Twitter has specific requirements for video dimensions. It’s essential to have a reasonable aspect ratio like 16:9 or 4:3, and the platform doesn’t allow odd numbers of pixels in the width or height. It’s also recommended to upload MP4 files for better compatibility.

Step 1: Install FFmpeg on Windows

  1. Open your command prompt.
  2. Type winget install ffmpeg and press enter.
  3. Say yes to all prompts and restart the terminal when installation is complete.

Method 1: Padding

Padding involves adding black bars to the height of your video to meet Twitter’s aspect ratio requirements. Here’s how to do it:

  1. Calculate the padding pixels. If your video’s width (iw) is 680 and the height (ih) is 480 (4:3 aspect ratio), the padding would be ((680*3 - 480*4)/8).

  2. Use the following FFmpeg command for padding:

    ffmpeg -i input.mp4 -vf "pad=width=iw:height=ih+padding:x=0:y=padding/2:color=black" -c:a copy output.mp4

    Replace padding with your calculated value.

Method 2: Cropping

Cropping is a simpler method where you remove parts of the video to meet the aspect ratio. Here’s how:

  1. Determine the crop width, crop height, x, and y values.

  2. Use the following FFmpeg command for cropping:

    ffmpeg -i input.mp4 -vf "crop=cw:ch:x:y" output.mp4

    Replace cw, ch, x, and y with your values.

If you don’t specify x and y then it will crop from the center.

Convert avi to mp4

If you need to convert avi to mp4 use following command

ffmpeg -i input.avi output.mp4

References