[FFmpeg-user] ffprobe -show_frames and coded_picture_number

[thljcl]

thljcl wrote
> Hm… Well, let’s put it to actual test, which should be a much better
> option than believing in either you or me. Do you currently have a source
> of 24 FPS which you think that it has “high speed motion”? If you
> seriously think that using the method I describe would lead to
> “unrealistic motion”, can you share such a source with me and allow me to
> do the encoding process? After doing the encoding process, I will upload
> the output file to SkyDrive and share it temporarily publicly. We can then
> all use our eyes to make our judgment. I do believe that an actual
> experiment would help me understand better. Thank you.
> 
> Oh, yes… Please make sure that the source you use is not too big or too
> lengthy. After all, it’s just meant to prove the hypothesis. I would
> prefer your source to have less than 10 minutes in length.

My main desktop PC is an All-In-One HP PC. The refresh rate of that display
is 60 Hz. The television set in my living room seems to be able to support
both refresh rate of 60 Hz and 50 Hz. It is a 50-inch LCD display. It is
connected to the set-top box for the Astro Satellite TV service, which
delivers contents on both 1080i and 720p, depending on the user’s
configuration. The frame rate of the Satellite TV service seems to be 50i or
25p. I have another 11.6-inch tablet/Ultrabook, which has an HDMI output as
well as a HD media player. I occasionally connect the tablet to the
television set. From what I’ve seen so far, I did watch videos of different
frame rates, including but not limited to 23.976 FPS, 24 FPS, 25 FPS, 29.97
FPS, and 30 FPS. Most of the time, I cannot tell the frame rate without
specifically checking the media info. The television programs produced by
different producers throughout the world and theatrical films did use
different frame rates. I supposed that if the software can decode the
content correctly we the users need not bother about the frame rates?

I did specifically choose 24 FPS as my chosen frame rate for the videos I
encoded, regardless of the frame rate of the source. Most of the time, I did
not notice any difference using my naked eyes on my displays. However, to
verify the claim of others that “unrealistic motion” could happen for 24-25
frame rate conversion by duplicating frame, I performed a test on the source
which has produced for the frame rate of 24 FPS. The source I used is an
open movie created in the year of 2010, called “Sintel” (Project “Durian”).
It’s a CGI-created animation using open-source software such as Blender. The
source of “Sintel” of lossless compression or uncompressed version is at
http://media.xiph.org/sintel/.

>From the sources, I created both 24-FPS version and 25-FPS version, which I
uploaded to http://sdrv.ms/14FXYb9. On my display, I could not tell the
difference with my naked eyes at most parts, other than at the end where the
credits are rolling. The lack of “motion blurring” causes the obvious
“jarring unrealistic motion” when the credits are rolling for the 25-FPS
version. I only used ffmpeg to duplicate frames. If I edit the frames by
adding some “motion blurring” or “transitional effects”, the “jarring
unrealistic motion” could be somewhat mitigated.

A single experiment is far from conclusive to prove anything. However, from
my experiences as well as this experiment, while duplicating/dropping frames
is not strictly perfect, it’s certainly an acceptable solution for many if
not most cases. The reasoning is mainly the properties of human visual
system. “Motion picture” is never “the picture that moves” but our visual
system makes us think that “it moves”.

Note: I may remove the “Sintel” from SkyDrive from August 21, 2013 onwards.
Please download them before the deadline if you want to see for yourself.



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