1080i/25Hz

Sony65

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Probably been a while since someone asked a dump question so here goes. Why does my TV show that I receive HD channels in 1080i/25Hz. Thought it should be 50Hz? Be gentle with any answers.... Incidentally it's connected to a terrestrial aerial.
 
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Interlaced uses a pair of frames (odd and even, 540 lines per frame).
25Hz is for a pair of frames, 50Hz is per frame.
 
Interlaced uses a pair of frames (odd and even, 540 lines per frame).
25Hz is for a pair of frames, 50Hz is per frame.
So is 25Hz correct for my TV as not sure I can change it anyway and if it were 50Hz which I think my last Pano TV had would I get a better quality picture?
 
No, half frames at 50Hz is full frames at 25Hz. It is a hangover from the way CRT TVs operated, mains frequency etc.
Technically the correct naming to 1080/50i and non interlaced is 1080/25p.
The 'p' stands for progressive.
 
No, half frames at 50Hz is full frames at 25Hz. It is a hangover from the way CRT TVs operated, mains frequency etc.
Technically the correct naming to 1080/50i and non interlaced is 1080/25p.
The 'p' stands for progressive.
OK thanks it just looked odd as it was the first time I noticed it yesterday and thought that I had set the TV up incorrectly or something but have no complaints with the PQ so all good. Tks.
 
Probably been a while since someone asked a dump question so here goes. Why does my TV show that I receive HD channels in 1080i/25Hz. Thought it should be 50Hz? Be gentle with any answers.... Incidentally it's connected to a terrestrial aerial.

Freeview-HD is pretty well all 1080p25. Freeview-HD kit was designed to dynamically switch from interlaced to progressive within a GOP (Group Of Pictures). Most content is now progressive.

General
ID : 16517 (0x4085)
Complete name : D:\FreeviewHD\The Homesman_20170521_2202.ts
Format : BDAV
Format/Info : Blu-ray Video
File size : 35.8 MiB
Duration : 1 min 24 s
Overall bit rate mode : Variable
Overall bit rate : 3 526 kb/s
FileExtension_Invalid : m2ts mts ssif

Video
ID : 101 (0x65)
Menu ID : 17472 (0x4440)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings, CABAC : Yes
Format settings, RefFrames : 4 frames
Format settings, GOP : M=4, N=12
Codec ID : 27
Duration : 1 min 23 s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 FPS
Standard : Component
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

Audio
ID : 102 (0x66)
Menu ID : 17472 (0x4440)
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Muxing mode : LATM
Codec ID : 17
Duration : 1 min 24 s
Bit rate mode : Variable
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Delay relative to video : -1 s 48 ms
Language : English
 
There's no dumb or even dump questions, and the other responders have explained that everything is ok. This is a bit of background...
When motion pictures commenced the experimenters realised that still frames repeated at above 20 frames a second gave the illusion of motion. To give themselves a little leeway they settled on 24 frames a second.
When TV commenced at 405 and later 625 line standards, the decision was made to use 25 full frames per second..in Europe. In the USA they went with 30 . In both cases this was due to the national electrical grids being at 50 and 60 Hz.
In order to reduce the amount of bandwidth or data being sent, the policy was that the 312 lines would be sent to fill up the entire screen, top to bottom leaving a gap between each line, and in the next 50 th of a second, another 312 lines would be sent, filling in the gaps. .. this is the interleaving. The human eye would not be able to respond quickly enough and would see a solid picture. This worked fine with the analogue CRT displays. Only as long as a signal was being received would an image exist on the screen.. there would be no memory effect.
With a LCD or oled, there is an entire block of memory dedicated to feeding the screen and it can be refreshed as often as the internal electronics will allow... You may have had the experience of say the signal dropping out and the image remaining static on an LCD screen for minutes
The newer standards allow for 50 full images to appear on the screen per second... 50p , this is richer in texture as it contains twice as much information.
As a final aside, the initial motion pictures people got it slightly wrong... While 24 pictures per second is ok for a small image directly in front, it's not so good for side on vision. Probably due to our ancestors desire to identify sabertooth tigers sneaking up, we are more sensitive to flicker in peripheral vision. As TVs get bigger, they engage more of this side vision . Hence luxury TVs and computer monitors are going for higher frame rates.
 
Thanks for the info it's overwhelming!! Just moving on a little when I watch TV through my Pano UB700 it shows as 1080p not sure what Hz but notice it's 1080p and not 1080i. Will the PQ be any different between the two as personally I can't see it but some of you may have a different opinion. Thanks in advance.
 
Basically at some point between the disc and the display panel it will get deinterlaced and the UB700 can do a very good job so nothing to worry about whether it is done there or in the TV.
 
Thanks for the info it's overwhelming!! Just moving on a little when I watch TV through my Pano UB700 it shows as 1080p not sure what Hz but notice it's 1080p and not 1080i. Will the PQ be any different between the two as personally I can't see it but some of you may have a different opinion. Thanks in advance.
The pq is basically set by the amount of information sent by the TV station. The digital electronics extracts out a frames worth, stores it in a block of memory and then keeps displaying that until the memory is overwritten with new data.
 
Delinterlacing can be more complex than that because the interlaced frames are actually taken at different times so there is movement.
This is why a good deinterlacer is worth the bother.
 
Yes trollslayer, but in essence, what I was saying is true. There was no value at this level of talking about A and B frames and the transmission of only the changes . Nor to talk about the increased data rates for3D
The electronics is being asked to take this information on the fly, decode it and load a block of memory, recycle this data and then add new data... There is no way a consumer can influence that on a TV.
On a computer, a precious few may have the expertise to code a codec and write to a video card, but that is a bit extreme.
 

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