Essentially the aspect ratio of a video is the ratio of its width to its height. Over the years there have been several different aspect ratios that have been popular, such as 4:3 that used to be the standard for broadcast television for many years.
Nowadays the most common aspect ratio is generally 16:9, which is what widescreen televisions and monitors generally use. However the popularity of mobile devices has made its vertical equivalent (9:16) just as popular, and also seen the rise of square aspect ratios (1:1) that are viewed as a compromise of sorts.
If you want to resize the aspect ratio of a video there are several methods that you could use – each with its own advantages and disadvantages:
- Stretching the video
Probably the ‘easiest’ way to resize your video’s aspect ratio is to simply set its frame to the new aspect ratio and then ‘stretch’ or ‘compress’ the video so that it fits. Unfortunately that approach will distort the image in the video, especially if the new aspect ratio is very different from the old one.
- Adding black bars to the video
Another common way to change the aspect ratio is to add black bars around them to make them fit the new aspect ratio without distorting the image. For example you could add black bars to the top and bottom of a 16:9 video to change it to 1:1.
- Cropping the video
By cropping your video and removing a section of it near the frame, you can essentially alter the aspect ratio directly – without any image distortion. However in order for this to be an option in the first place the video itself needs to have areas that you can remove without adversely affecting its content.
- Cropping and stretching the video
The final option is the one that is often the most applicable to videos in general and involves both cropping and stretching the video. Normally cropping is used first to make the video as close to the target aspect ratio as possible, and then the video is stretched the remainder of the way.
Although some image distortion will take place, in theory it should be minimal due to the fact that it was first cropped. Some video resizer tools may even do this automatically.
As you can see each option has its advantages and disadvantages, and it is up to you to select the one that you feel will suit your video best. It may help to use an aspect ratio calculator to figure out the dimensions you’ll need for your video. Additionally if in doubt, you could always try each option individually and observe how it affects your video.