30 Oct
2014
30 Oct
'14
11:36 p.m.
On Fri, 31 Oct 2014 00:07:32 +0100
Carsten Kurz <audiovisual(a)t-online.de> wrote:
I see how it could be annoying... there's probably no reason to ignore
pixel AR information if it exists in a source file.
Best,
Carl
Am 30.10.2014 um 23:26 schrieb Carl Hetherington:
OK, I see. I never would have guessed that anyone would want to pad,
say, a 1024x576 video on all sides with black and put it on a 2K cinema
screen... is that really better than scaling it up? Can't you just
tell people to sit further back in the screen? ;)
How could you put an unscaled version of this
file into a DCP at
all? If my maths is right the pixel aspect ratio is 1.42:1, so
aren't you going to need "upscaling" of some description to map it
to the square-pixel DCP?
Oh, of course it would have to be scaled, the problem right now is
that I can not put it into a DCP 'properly', unscaled WITH the proper
aspect ratio correction. The 'no scale' option was brought up (I
think in this list) so that one could use any size footage without
upscaling, just by padding top/bottom/sides with black. Now that
works for real square pixel footage - but not for 16:9/anamorphic,
because there is no option to turn it into square pixels without
upscaling - the only option to get it into 16:9 AR is to apply a
scale to 16:9 - but that also blows it up to 1920*1080 in a flat
container. I wouldn't care for this specific video, as I
could turn it into what
I wanted with the 16:9 option - but then I tried to find out wether
DCP-o-matic ommited a 16:9 flag in the file, loaded it into media
players, tested DCP-o-matic with a now 'normal' 16:9 DVD VOB file -
and found the same issue with it.
Yes, it currently makes no attempt to look at pixel AR information.
So, essentially, we can not create a flat container
from a 16:9 VOB
with ONLY the Pixel AR corrected to 1024/768 and padded with black on
all sides. And that's what I thought is a missing link if we want to
make sense to that 'no scale' option. You are of course right that
from a signal processing perspective, there is not much difference
between an anamorphic->square pixel scale, and an upscale to
1920/1080. But I think the no-scale option has some good uses, so it
should work with non-square pixels as well, because so much content
is still 16:9/non-square.
As I said above... I had not anticipated the desire to have true
no-scale, to put a small image in the middle of a big screen...
Maybe we
should ditch the default scale-to option and instead guess
it from the input AR and pixel AR? I guess that would be
extensible if and when DCP-o-matic tries to detect
letterboxing/pillarboxing of inputs.
Funny thing - yesterday I talked to a fellow projectionist and he
told me he was still using DVD-o-matic. I told him he should make the
switch, there is nothing to worry, and he said he would. Then he
asked me why the hell would DVD-o-matic always 'stretch' content
vertically when he first imports it. It seemed annoying to him,
although not much work to correct. I didn't think about that much
until I imported that AVI file today and noticed essentially the same
behaviour. Obviously he converts a lot of 16:9 anamorphic stuff and
always has to correct the AR first. Admittedly, I don't remember how
DVD-o-matic arranged the scaling options back then. I remember you
reorganized them at some point because they became too confusing and
partly redundant.