When is a video (file) HD?

Consumer Electronics
#1

Hey ALL ;),

According to my research If a video has a height of:
> 576 then its DVD Quality (for PAL)
> 720 then its 720p / 720i
> 1080 then its 1080p / 1080i

Although I believe it would depend on the source and the codec used as to whether a video file can be truly described as being HD.

But what happens if the video file does not conform to any of the video heights? For instance if the video has a height of 588 or 905 - does it make them 588p (/ 588i) and 905p (/ 905i)

Also I would to point out that some video files claim to be 1080p when there dimensions are 1900 x 800 so what does that make this?

Is there an easy way of checking if a video file is HD?

Thanks

#2

Maximum resolution for standard definition video is 720 x 576 (PAL), or 720 x 480 (NTSC). You’ll find that some people will convert standard definition wide screen anamorphic video found in dvds (non-square pixels) to a larger square pixel format, like an 852 x 480 avi file, but the quality does not go up when doing so, and it won’t play on a standard dvd player which has limits on resolution size.

Anything above the SD resolutions can be described as HD, though most of us would define 720p as the start of high definition resolutions. 720p is 1280 x 720 resolution.

There were some intermediate resolutions in certain countries, like 576p(50fps), but they have been replaced in tv transmissions by 720p or 1080i. 576p was also called EDTV.

Most of the odd sizes you see in “high def” files are due to people cutting out the black bars on wide screen video. They were probably from 1080p blu ray sources, then converted to something smaller to make them easier to download.

And just because they are larger resolution than standard video doesn’t make them high quality. If the bitrate is reduced too far, to make the files smaller, the quality of the video can become quite poor, even when using a fine codec like H264.

#3

The truth is that there is no such thing as a technical definition for “HD”. As mentioned, the amount of compression has far more to do with perceived picture quality than vertical resolution does. IOW, you can easily find examples of “HD” video for streaming or download that have far less image quality than a quality SD version of the same material.

Another common point of confusion is OAR or “scope” presentations of films in a 16:9 format that are letterboxed. These will often carry a resolution number that’s less than 1080 or 720 because the black bars are encoded into the video and are not counted as lines of resolution. But the fact remains that they are actually 1080 or 720.

#4

Thanks alot, that was my sort of understanding from finding no definitive answer when googling.

Thanks, again