Why MediaInfo says 25fps while my video is actually 50i ?

[Sam0403]

My camcorder recorded video in 1080/50i, but when I checked the information in MediaInfo it showed as 25fps interlaced. I think it should show as 50fps interlaced.
Any reason why MediaInfo did so?

Original information from MediaInfo:


General
ID : 1 (0x1)
Complete name : D:\test files\MTS\MTS\00074.MTS
Format : BDAV
Format/Info : Blu-ray Video
File size : 43.0 MiB
Duration : 1mn 4s
Overall bit rate mode : Variable
Overall bit rate : 5 618 Kbps
Maximum Overall bit rate : 18.0 Mbps

Video
ID : 4113 (0x1011)
Menu ID : 1 (0x1)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Format settings, GOP : M=3, N=12
Codec ID : 27
Duration : 1mn 4s
Bit rate mode : Variable
Bit rate : 5 001 Kbps
Maximum bit rate : 16.8 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Top Field First
Bits/(Pixel*Frame) : 0.096
Stream size : 38.3 MiB (89%)

Audio
ID : 4352 (0x1100)
Menu ID : 1 (0x1)
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Format settings, Endianness : Big
Codec ID : 129
Duration : 1mn 4s
Bit rate mode : Constant
Bit rate : 384 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Delay relative to video : -80ms
Stream size : 2.95 MiB (7%)

Text
ID : 4608 (0x1200)
Menu ID : 1 (0x1)
Format : PGS
Codec ID : 144
Duration : 1mn 3s
Delay relative to video : -80ms

[racer-x]

50i signifies 50 fields per second. The actual framerate is 25 fps. Each frame is comprised of two fields (upper and lower field) and that's what makes it interlaced as apposed to progressive which uses no fields.

[manono]

My camcorder recorded video in 1080/50i, but when I checked the information in MediaInfo it showed as 25fps interlaced. I think it should show as 50fps interlaced.
Any reason why MediaInfo did so?

It said 25fps because that's what it is. Why should it say 50 frames per second when it's not? It's 25 frames per second or 50 fields per second. Or 25i. All the same. Unfortunately, 50i has taken over and it's really confused things because it means 50 fields per second. But it's certainly not 50fps (where the 'f' should mean 'frames').

So, 25fps, yes. 25i, yes. 50i, yes (although I think it's a really dumb idea because it leads to confusion such as yours). 50fps (or 50fps interlaced), no.

[jagabo]

Yes, 50i is just the new name for 25i. Blame the Marketing department.

[Sam0403]

Thank you! But I think...I am lost again

[jagabo]

50i is exactly the same thing as 25i. Marketing just changed the name because they like bigger numbers. If you had a product that was exactly the same as your competitors, and you marketed it as 25i but you competitor marketed it as 50i, which do you think will get more sales? Once one company started calling 25i 50i all the others had to follow.

Each frame of a 25i video (25 frames per second, interlaced) contains two half-pictures, one in all the even numbered scan lines (ie, every other scan line of the video), one in all the odd numbered scan lines. Each half-picture, called a field, is to be displayed alone, sequentially. So you see 50 different fields every second. This gives smoother motion at the cost of resolution.

[Sam0403]

Thanks again jagabo for the explanation!!! Now I get some sense.
But when I played that "25i" MTS video in VLC and checked the media information within the player it showed me "Frame rate:50".

Those confusing things gonna make me pull all my hair out...

[jagabo]

Thanks again jagabo for the explanation!!! Now I get some sense.
But when I played that "25i" MTS video in VLC and checked the media information within the player it showed me "Frame rate:50".

Since the computer monitor is progressive VLC has to turn each field into a frame to display it. So 50 fields per second becomes 50 frames per second at VLC's output. And just to make it more confusing, on screen it's probably 60 frames per second (one frame out of every 5 is shown twice) because most LCD monitors run at 60 Hz refresh. If you watch a smooth panning shot you'll see 10 little jerks every second.

[Sam0403]

I thank you very much jagabo for your kind help all the way!!!

[Stears555]

Thanks again jagabo for the explanation!!! Now I get some sense.
But when I played that "25i" MTS video in VLC and checked the media information within the player it showed me "Frame rate:50".

Since the computer monitor is progressive VLC has to turn each field into a frame to display it. So 50 fields per second becomes 50 frames per second at VLC's output. And just to make it more confusing, on screen it's probably 60 frames per second (one frame out of every 5 is shown twice) because most LCD monitors run at 60 Hz refresh. If you watch a smooth panning shot you'll see 10 little jerks every second.

Are there Jerks in the era of modern videocards?

[jagabo]

Are there Jerks in the era of modern videocards?

Any time the monitor refresh rate isn't an integer multiple of the video frame rate the will be jerks.