What's the difference between video quality and resolution?

Question

Video

Friends, who can clearly explain what is the difference between the "quality" of a video (BD, DVD or TV / Web) and its extension?
In an app, I'm trying to display an indication for a video correctly. But I have a video marked "BD", but the maximum size is 720p, and sometimes a video marked "TV" and 1080p.

Answer 1

Video quality is measured primarily in bitrate (in Windows Explorer, it's "total bitrate"), not "BD, DVD, or TV/Web". What you call quality is a banal video source (and I'm not sure if it's real). Blu-ray, DVD or Internet.
Resolution is the height and width of the video frames. Basically 720P, 1080P, 2160P (4K) and a whole mountain of everything below 720P - you can call them all "SD".
There is no real connection between the video source and resolution, but with quality it is quite possible. Blu-ray files are usually written with a high bitrate, because it is much larger than DVD. But you can put anything on the Internet, there the quality is not regulated in any way, and knowing that the source is "Web", it is impossible to assume the quality.

In an app, I'm trying to display an indication for a video correctly.

Use resolution and bitrate. Keep in mind that even 4K video can be compressed in such a way that "mother's mother won't know" if the bitrate is set too low.

Answer 2

The term "quality" does not have a strict meaning, it is used by many from the bulldozer. If you want to say something meaningful about a video, it's best not to use it as a rule.
Resolution is the size in pixels, either linear (along the sides or height) or area (total, usually in megapixels).
What really describes the video instead of "quality" is bitrate (volume per unit of duration), compression rate, codec profile, number of bits per color component.
Saying "video in FullHD quality" is illiterate, because FullHD captures only the resolution (number of pixels), but not everything else. Because "video in FullHD resolution."

Answer 3

Not only the generally accepted bitrate is responsible for the quality, but also the compression algorithm. Why compression - because an uncompressed stream takes up several orders of magnitude more space on the disk than it makes sense, do you like minute-long clips that take up several terabytes.
It is not enough to compare the uncompressed original pixel by pixel and assume that the greater the discrepancy, the worse the quality. Modern codecs are able to take into account human perception and use the shortcomings of vision to keep the visible in the video stream and remove the unnecessary.
Therefore, the concept of quality is difficult to formalize.