[opendtv] Re: Global standard

  • From: Olivier Houot <olho_avatar_i@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 04 May 2012 15:43:16 +0200

Craig Birkmaier wrote:
>It is time to let go of interlace, 59.94, and maybe even 50P. A more 
>logical heirarchy for the future would be:

>24P for film

>36P for talking head and low motion video

>60 and/or 72P for rapid motion.

Regarding the choice of a universal frame rate,

considering some papers by Mark Shubin and some considerations of John
Watkinson on the need for really high frame rate for realistic motion
rendition and the efficiency of compression for the highly
correlated/redundant input material that such rates would produces, it
would seem natural to settle on 300 Hz, which is no longer unrealistic
with the current state of technical affairs.

This achieves compatibility with both 50 Hz and 60 Hz legacy material by
simple frame duplication. 

It brings on the table the superior compatibility with films of
50-multiple standards ("PAL speed up"), in preference to the
motion-crippling 3:2 pulldown workaround, though in principle both could
still be used.
There is still the possibility of using motion compensation for those
who accept neither of those compromises.

At the beginning, one could still use either 50P or 60P cameras and
duplicate frames. So one could shoot in every country at the correct
rate to avoid beating with the mains frequency.
On LCD (non pulsed) displays, the repeated frames would simply merge
into a single one with a longer display time, essentially recreating the
original captures rate. 
Because of the redundancy of duplicated frames, compressed bit rate
would indeed not be much higher than the current one, or equal if we
simply transmit 50 or 60P and let the receiver to the duplication.

Once the standard is deployed, with the improvement in camera
technology, it will be possible to capture at 75 fps, then 150 fps, then
finally the full 300 fps and still retain full compatibility in the
process (though one should be prepared to allocate more bandwidth when
that happens, unless compression technology has advanced to the point
where it can absorb the difference).

This slightly favours the 50 Hz world when it comes to shooting in
artificial light, as it would operate correcly at 50, 150 and 300 fps,
while 60 Hz lighting could only use 60 and 300. But 50 Hz is what most
countries of the world use, so by virtue of numbers, it should be given
priority. Also it is more universal, being more film friendly, while 60
Hz is essentially only compatible with itself.

Even if we don't fully use the 300 Hz capability initially, it will
still be very useful as a unifying standard. It would require little or
no initial upgrade of transmission facilities to achieve this, what it
needs is a 300 Hz capable display, which the manufacturers seem to
already provide. In the case of external set top boxes receivers,
though, what would be missing would be a standard to transmit
uncompressed 300 fps from the box to the display (about 7.5 Gbps in
4:2:0, 8 bits, 2D, within capability of HDMI 1.3 hardware). This is less
of a problem if the receiver is integrated into the display.

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