What is with the fixation on 60fps *or* 30fps with consoles?
- Thread starter kyleb
- Start date
function said:So .. 1080i or 720p, anyone?
LOL we're having that kind of discussion (for the 928392th time) on the avforums right about now... http://www.avforums.com/forums/showthread.php?p=1974078#post1974078
Hmmm. Lots of opinions later and I'm still none the wiser!
We have people saying there's no 60fps broadcast, only 30fps broadcasts, but you get movement ofa new frame every refresh at a rate of 60 frames per second though you're only supplying a new image every 30th of a second, but cameras do capture interlaced 60fps motion, but it's only broadcast at half speed but 30 frame per second interlaced 60 frame per second motion.
Okay, which of these is true...
1) A camera records 60 fields (half height frames) or frames per second. Each field in the broadcast represents a different 60th second of the footage. - 60 different images updated 60 times a second on alternating lines.
2) A camera records 30 full height frames per second. Each field in the broadcast is an odd or even interlaced field. - 30 different images updated 60 times a second
Note on definitions:
A field is a half-height image displayed on alternating lines. Odd and even lines are offset by one line in the vertical.
A frame is a full resolution picture with every line rendered.
A 60 hz broadcast is sending 60 fields per second.
I think the confusion is in terminology as Gerry suggests, and the reality is number 1 above. 60 fields are captured and broadcast and displayed, for 60 seperate images, 30 full frames of interleaved image with each frame showing motion from two different slices in time.
We have people saying there's no 60fps broadcast, only 30fps broadcasts, but you get movement ofa new frame every refresh at a rate of 60 frames per second though you're only supplying a new image every 30th of a second, but cameras do capture interlaced 60fps motion, but it's only broadcast at half speed but 30 frame per second interlaced 60 frame per second motion.
Okay, which of these is true...
1) A camera records 60 fields (half height frames) or frames per second. Each field in the broadcast represents a different 60th second of the footage. - 60 different images updated 60 times a second on alternating lines.
2) A camera records 30 full height frames per second. Each field in the broadcast is an odd or even interlaced field. - 30 different images updated 60 times a second
Note on definitions:
A field is a half-height image displayed on alternating lines. Odd and even lines are offset by one line in the vertical.
A frame is a full resolution picture with every line rendered.
A 60 hz broadcast is sending 60 fields per second.
I think the confusion is in terminology as Gerry suggests, and the reality is number 1 above. 60 fields are captured and broadcast and displayed, for 60 seperate images, 30 full frames of interleaved image with each frame showing motion from two different slices in time.
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It's one of those "everyone's right, everyone's wrong" kind of semantics-related scenarios.
london-boy said:
I'm not too surprised you have trouble finding solid information out there - it's thin on the ground whereas less accurate stuff is plentiful. For some reason, even TV engineers themselves, or other "professionals" working with this stuff can't seem to get their head around the concepts.
Everything *used* to be at 25 or 30 fps because it was all shot on film and the TV systems were designed to show stuff that only really needed to update at 24fps but with as much resolution as possible. The most complex "algorithm" used was to either repeat fields or speed everything up.
As far as some experts are concerned, nothing has progressed since then. Digital video apparently never happened...
It's the same as this persistant falacy that the human eye can't see 50Hz movement. People just keep treading out the same old tired myths even when the truth is quite literaly staring us in the face.
The real situation is far more complicated.
Given how many stages the picture goes through between "something happening in the real world" and "light hits your eye", it's no surprise that quite a lot of those stages mangle the picture in interesting ways, even assuming you have a 50/60 image to start with.
Obviously anything shot on film is ruled out straight away. Stuff on shot on video might well start off OK but get deinterlaced at source and processed (for example, converted to an mpeg stream for storage or broadcast).
Even when it gets to your TV it's not safe - many flat-panel displays or modern CRTs do their own deinterlacing and some are not entirely smart, effectively building a 30/25fps progressive signal out of something that really should be 60/50.
These days I can definitely see smooth motion combined with combing artefacts while watching some TV programs. I would only get this if the source material is at 50fps and isn't being deinterlaced. The smarter deinterlace filter I used to use could make a reasonable stab of removing the combing without killing the motion, but the current one I use doesn't do that. Either is better than the stupid default filters which deinterlace to 30/25...
So it's definitely there, I see it every day, but I'm not at all surprised that you could be watching the same stuff and not being seeing it, nor that you can't find concrete information about it.
Thanks Wibble
None the wiser, but thanks!
None the wiser, but thanks!
In essence it differs on source. Anything shot on film will on have 30 images per second, with doubled fields for broadcast. Whereas anything on video could be 60 images per second at half-height.
No. Films may be 24fps, but video cameras will be capturing fields at 50/60Hz. In effect you are getting a 50/60Hz update rate.london-boy said:No. Hz and fps are 2 different things.
That's the refresh rate of the TV and how the 60Hz interlaced system works.
The material runs at 30fps, meaning the recordings were made at 30fps (24fps for movies). The TV will then display those in an interlaced manner at 60Hz..
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It is (A).. (BTW "Half height" is a bad term!)Shifty Geezer said:
Well no.... ON PAL systems the 24fps film is sped up slightly to get 25fps which are then divided into the two fields.Shifty Geezer said:
On NTSC they use 3:2 pull down which means that that they mix pairs of film frames together to form the frames of the TV signal at ~30hz. IIRC, if you have film frames A B C D, then you'll get a pattern of FIELDS that looks like A1 A2 A1 B2 B1 C2 C1 C2 D1 D2.... where 1 and 2 represent the odd and even sets of lines from the frames.
BUY YOURSELF a video camera, film something moving and pause the results. You will see that the fields are captured at double the frame rate.Shifty Geezer said:
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How can they speed up the film to 25fps on PAL? They'd need to increase the audio playback too. Do we have speeded up movies?!
Yes.Shifty Geezer said:How can they speed up the film to 25fps on PAL? They'd need to increase the audio playback too. Do we have speeded up movies?!
Haven't you ever heard the stories of people complaining "I bought T&tanic on DVD and it's been cut.... in the cinema it is 10 years long but my DVD is only 9. I want the full version"?
Apparently some actors find it odd to hear themselves speaking with a slightly higher pitch.
FWIW, AFAICS, an NTSC version would actually be a tiny bit slower.
Nope. Never heard anything of the like. Certainly LOTR didn't seem any shorter on DVD. How does Region encoding work then? When my friend watches a region 1 DVD on his PAL TV how is it encoded? What about when a PAL DVD is ripped to MemoryStick for play in a PSP?Simon F said:
Shifty Geezer said:
Well when you watch a R1 DVD on a PAL TV, your TV would either work in 60Hz mode - most PAL TVs do - or the DVD player converts the signal into PAL.
Both are possible, as they are entirely on the content side and there's no technical reason to not broadcast 60 different fields per second regarding transmission and TV sets. Though, as MrWibble said, any additional processing of the footage could mean a deinterlacing step is necessary so you won't get 60 different fields.Shifty Geezer said:
Simon F said:
I know, but some players do. Not sure what the end result is though.
Most PAL TVs are perfectly fine with NTSC signals these days so R1 DVDs are a non-issue really.
From next year we'll have a new and improved list of issues to worry about, with HDTV resolutions to choose from, and the resolutions themselves being either at 50Hz or 60Hz, which is still unclear at the moment - Sky will broadcast in 50Hz but i assume consoles will output at 60Hz... And the problem is that some HDTVs sold in the UK these days only accept one of the 2 refresh rates...
What a mess... We'll have a total of 10 configs... 480i/p/50/60, 720p/50/60, 1080i/p/50/60...
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