1080p30 vs 1080p60
dipu...@hotmail.com
Hi
Does 1080p60 deliver a better viewing experience than 1080p30? I have
looked around in the newsgroups. Most of the discussions focus on
interlace vs progressive. But with progressive video, is there a
significant(?) difference between 30 or 60 frames per second? Even if
we assume that the source was recorded at 60 fps, can the human eye
( and brain) distinguish any motion related difference between 30 fps
and 60 fps? Old technologies like CRT needed higher refresh rate to
avoid brightness flicker. Newer technologies like LCD or Plasma should
not have that problem.
Is 1080p60 just a marketing hype? I have even heard of 1080p120. What
am I missing?
-Dipu
Jan B
>
>Hi
>
>Does 1080p60 deliver a better viewing experience than 1080p30? I have
>looked around in the newsgroups. Most of the discussions focus on
>interlace vs progressive. But with progressive video, is there a
>significant(?) difference between 30 or 60 frames per second? Even if
>we assume that the source was recorded at 60 fps, can the human eye
>( and brain) distinguish any motion related difference between 30 fps
>and 60 fps?
The way we display film material on TV in europe gives 25 individual
frames (25 object positions) per second. (This is displaying the film
frames one by one but at 25Hz instead of 24.)
That is not enough to perceive a smooth motion other than if the
motion is very slow or the individual frames are blured from movement
during the exposure time. Many film scenes are produced with too sharp
individual frames to give a smooth motion at 25Hz.
The performance from 30Hz should improve but I don't know if it
solves the problem.
50Hz motion (50Hz field frequency from real interlaced material like
TV broadcast) gives me what I would call "smooth motion".
>Old technologies like CRT needed higher refresh rate to
>avoid brightness flicker. Newer technologies like LCD or Plasma should
>not have that problem.
Plasma panel blinks if the refresh frequency is too low. Look for the
difference in plasma panels with "100Hz" feature. This comes from the
pixels turning on/off to display a certain brightness.
The problem with LCD and I believe also with plasma showing bright
objects is the opposite that comes from displaying moving objects at
the same position for too long time. This creates motion blur in our
eyes.
>Is 1080p60 just a marketing hype? I have even heard of 1080p120. What
>am I missing?
The 100/120 Hz you heard of is to decrease the time a moving object is
displayed at the same position. The benefit is a sharper motion also
at 50/60Hz content update. (This is not a signal type, yet?, but a
processing internal to the display.)
/Jan
Alan
>The way we display film material on TV in europe gives 25 individual
>frames (25 object positions) per second. (This is displaying the film
>frames one by one but at 25Hz instead of 24.)
>
>That is not enough to perceive a smooth motion other than if the
>motion is very slow or the individual frames are blured from movement
>during the exposure time. Many film scenes are produced with too sharp
>individual frames to give a smooth motion at 25Hz.
I have read and noticed that if the film is shot with long enough
exposure times that it is blurred in the frames, the motion appears
smoother, just as you note.
>The performance from 30Hz should improve but I don't know if it
>solves the problem.
>
>50Hz motion (50Hz field frequency from real interlaced material like
>TV broadcast) gives me what I would call "smooth motion".
And, 60 hz field frequency interlaced material gives visibly smoother
motion. Once you recognize the difference it is noticable.
>The problem with LCD and I believe also with plasma showing bright
>objects is the opposite that comes from displaying moving objects at
>the same position for too long time. This creates motion blur in our
>eyes.
Yes, exactly. A very similar effect to the double or triple flashing
of single film frames in projection.
Alan
Alan F
What are your video sources for 30p, besides maybe a computer? Movies
and TV shows shot on film in the US are shot at 24 frames per second or
24p. Video cameras for SD and 1080i HD are 60i except for 720p at 60p
(yes, this is simplified answer).
The human eye and brain can detect a difference between a 30 frames
per second and 60 frames per second update, which is why 60i is the
prevalent video standard (and 50i for PAL systems). 60i does NOT equal
30p. Movies have long been shot at 24 fps, which create this "movie"
look that people are used to. So we now have HD video cameras that shoot
at 1080/24p to get that movie feel.
1080/120p is presumably the 120 Hz refresh rate pushed for some LCD
screen to get rid of judder from 24p sources and to eliminate motion
smear. Except for some specialized equipment or PCs, you won't see 120p
video sources.
Alan F
phil-new...@ipal.net
You can get rid if the judder from p24 sources by encoding the video
directly in p24. An LCD might leave each frame on for a long time.
Other display technology could up the rate to some multiple of 24 such
as 48, 72, 96, or 120.
Or we could push everything up to 600 frames per second and that would
be an exact multiple of all the common frame rates :-)
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-200...@ipal.net |
|------------------------------------/-------------------------------------|
Jan B
The "judder in 24p" is the 'regular' judder due to the low frame rate.
(Perhaps you are thinking 'irregular' judder from 24Hz transfered in
60Hz 3:2 sequenced format.)
> An LCD might leave each frame on for a long time.
>Other display technology could up the rate to some multiple of 24 such
>as 48, 72, 96, or 120.
This does not remove the 'regular' 24Hz judder. If the same frame
content is repeated it only reduces the blinking effect (for those
implementations that 'blink".
Combining this with "motion estimated frame interpolation" it can
reduce the 24Hz judder.
There are also some different techniques in "120Hz" displays, where
for instance Sony SXRD projectors with 120Hz Motionflow describes that
it inserts black frames. This is a way to "start blinking" in order to
reduce the time each frame is displayed at the same position.
>Or we could push everything up to 600 frames per second and that would
>be an exact multiple of all the common frame rates :-)
Or switch the update frequency between 100 and 120 ...
/Jan