Confused about 1080p

[gauche]

Hi there,

Hypothetically speaking, if I were to download a torrent that claimed to be 1080p, and then check the .mkv file in MediaInfo to find that it is less than 1080 pixels in height, would that be because:

1. The person uploading the torrent lied.
2. MediaInfo is broken and does not report the video size correctly.
3. Something else is going on.

Thanks

[manono]

It could be the source was 1080p, and the encoder just cropped off the black bars to make it 1920x820 or whatever.

[raffie]

Aspect ratios in film are variable, and since movies are always wider than the 16/9 standard, the width will always be 1920, but the height is a variable at a max of 1080 pixels. Except when the source material is cropped in width, then you get full 190x1080.

[jagabo]

Note that many movies are wider than 16:9 (1.78:1). When these are saved in a 16:9 1920x1080 frame the width of the movie fills the 1920 pixels wide frame but the height does not fill the full 1080 scan lines. So black bars are added top and bottom to fill out the frame. Since MKV doesn't have to have the full 1080 lines (unlike Blu-ray and broadcast TV which must have a full 1920x1080 frame) the poster can crop away the black bars. A 2.35:1 movie will occupy about 816 lines of 1080 line frame.

Another possibility is that the poster started with a 1080p video and reduced the frame size before posting in order to make a smaller file. So 1920x1080 may have been shrunken to 1280x720, then compressed.

[gauche]

Thanks people - that makes sense.