Width/height vs. aspect ratio

[David1105]

MediaInfo.exe returns info of videos with width, height, and aspect ratio.

However, it often shows that ratio isn't equal to width/height.

Is there explanation for this "mis-matching"?

When converting a video and to keep the original aspect ratio in the output video, what's the proper calculation for the width or height of the output video according to the width/height and aspect ratio?

Thanks!

[Dark Shikari]

The aspect ratio can refer to an amount by which every pixel is stretched from the source, or the aspect ratio of the image. They're often not the same thing.

[David1105]

The aspect ratio can refer to an amount by which every pixel is stretched from the source, or the aspect ratio of the image. They're often not the same thing.

So, in the case of "mis-matching" of MediaInfo.exe, the aspect ratio is the AR of pixel, not the AR of the video image?

So to avoid the distortion of video after converting, should we keep the AR of pixel the same?

To avoid warpping of video, should we keep the AR of image the same?

Also, for the switch "-aspect" of ffmpeg.exe, does the AR switch refer to the AR of pixel?

Last, whenever such "mis-matching", can we safely say that the pixel is stretched, NOT squared anymore?