[FFmpeg-user] ffprobe -show_frames and coded_picture_number

thljcl jiachielee at live.com
Sat Aug 10 23:40:25 CEST 2013

I do have experiences over changing frame rate from 25 FPS, 29.97 FPS, and 30
FPS to 24 FPS using the method I described. As far as my eyes are concerned,
I do not have the so-called “unrealistic motion” issues. Some people have
believed that higher frame rate is required for more realistic motion.
Without regards to human eyes or perceptions, there is no such thing as
“absolute motion” as Laws of Physics are equivalent to all inertial frame of
references; depending on which postulate you use to derive the theory of
special relativity, such a statement could be regarded as either
“consequence” or “postulate”. That said, human visual perception has its own
properties; what we see does not necessarily represents the actual motion
relative to us as an observer. Generally, our eyes take time to capture
visual information; hence our visual perception is actually formed by
information we received from different time. That’s why we observe the
effect of “motion blurring” from “fast-moving object”. In a way of speaking,
“motion blurring” effect we observe is similar to the camera, which also
requires time to capture electromagnetic radiation from different time. Due
to our day-to-day experience, it’s hence more realistic to have “motion
blurring” effect from fast-moving object to our human eyes.
Generally speaking, human eyes are able to differentiate 12-15 images every
second by perceiving them individually. In other words, the frame rate of 24
FPS, 25 FPS, 29.97 FPS, 30 FPS, or 60 FPS all create the illusion of motion
picture, which we cannot actually know the frame rate using our naked eyes.
Theoretically speaking, if a camera is able to capture high-resolution image
at a very high frame rate on high-speed moving object, the “motion blurring”
effect would be lessened or disappear for individual frames. Hence, dropping
the frames to achieve lower frame rate of 24 FPS would actually result in
“less realistic” motion. It’s possible to add “special effect” with software
to make the motion “more realistic” to our eyes. That said, we were talking
about perhaps from 300 FPS to 24 FPS. For the common frame rate used by
different standard such as “24 FPS”, “25 FPS”, “29.97 FPS, etc., conversion
between them would almost certainly would not result any difference to human
naked eyes by duplicating and dropping frames.
As a matter of fact, most LCD displays can only have up to 60 Hz of refresh
rate. That means, even if the video does have very high frame rate, it would
become somewhat unrealistic to human eyes because of the lack of “motion
blurring” effect and the low refresh rate of the display. Only when both the
display has similarly high refresh rate and at the same time the video does
have very high frame rate, the properties of human visual system would
create “motion blurring” effect just as we actually see the actual motion of
the object.

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