FFMPEG add black bars to a image if the video input is not 16:9

Question

So I'm playing with ffmpeg and I have the command currently:

"ffmpeg_path?-ss?seek_time?-i?input_video_path?-vframes?1?-f?mjpeg?output_image_path?2<&1"

The issue that I'm facing is that for example I have a vertical video from a mobile phone the output image will be streched to 16:9, what I would like to do is to add black bars to the side of the image if the input is not in a 16:9 format.

Any suggestions or ideas on how I could do that?

Thank you!

Answer 1

Use the pad filter. The same documentation includes an exact example of what you want:

• Pad the input to get a final w/h ratio of 16:9:

pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"

The filter can be specified using the -vf option:

ffmpeg -ss <time> -i <input> -vframes 1 -f mjpeg -vf pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2" <output>