[opendtv] Re: Pan-scan-zoom
- From: Kilroy Hughes <Kilroy.Hughes@xxxxxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 9 Oct 2009 23:23:49 +0000
Where I landed was specifying 3 different formats for the "3 screens" and
assuming some selection is possible so that a "portable definition", standard
definition, or high definition device can pick the file/stream it needs. That
is driven as much by the constraints of bitrate and file size as the need to
format differently for different screens (which is probably the exception
rather than the rule, unless portable video takes off and earns special
editorial treatment).
If you want "fast start" viewing via streaming or progressive download, if you
are dealing with metered bandwidth, battery life, Wi-Fi networks, DSL, etc.;
you don't want "one size fits all" 20 Mbps Blu-ray quality HD files that take a
hours to download to your phone and an extra battery to watch a 15 minute
newscast in 416x320 display. The decoder chips are getting powerful and some
portable devices (Zune comes to mind) can output HD even though the internal
display can't show it, but you need lower resolution files for lower size and
bitrate.
If a publisher is making a "mobisode", they may make some esthetic edits
different from the SD or HD version knowing roughly how that file size will be
used. Doing it in metadata is a chicken/egg problem because all devices won't
support it so the publisher can't rely on it, and unless all publishers are
going to put it in content, device makers aren't going to add and hype the
(theoretical) feature. That would be like a device maker trying to hype
pan/scan, which is built into every DVD player, but zero content (other than
default center coordinates), so who cares?.
When Hollywood generates a 4:3 version, they have a human edit the movie,
intercut between two gun fighters talking rather than a wide shot of both, tilt
scan wide shots, crop one and two shots, new titles and credits, etc. That
typically goes to multiple delivery formats that don't have metadata driven
"dynamic edit bays" in the decoder. So, there wasn't much enthusiasm for adding
a pan/scan work flow (also featuring no tools and another test disc to make and
try on a room full of players to see what it actually looked like ... on
average).
Most of the Hulu, NetFlix, etc. streaming and "over the top TV" you see today
is using adaptive bitrate streaming, where different tracks are being played
every few seconds in response to instantaneous network conditions. Tracks of
the same content encoded at different bitrates and even resolutions and
subsampling (e.g. 1440x1080 16:9 like HD Cam) are switched seamlessly to
deliver video without frame drops or long buffering delays at whatever quality
is allowed by network throughput, error rate, latency, etc. The PCs, Blu-ray
players, Internet TVs, etc. playing Internet video just pay attention to the
sample aspect ratio and encoded actual picture height/Width info in the
elementary stream to frame it for the screen and scale encoded resolutions and
sample shapes so switching is rarely noticed by viewers (as slight changes in
"softness").
Again, the adaptation is happening on the front end for the benefit of the
network, which is usually more constrained that decoders and displays.
Kilroy Hughes
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of Stessen, Jeroen
Sent: Thursday, October 08, 2009 7:15 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Pan-scan-zoom
Hello,
John Shutt wrote:
> A brilliant concept,
Thank you. At least it's better than simulcasting two optimized
productions (HD and SD). I find it hard to believe that down-sampling
the entire image would generally be the best solution. In that case
we would not need all that nervous follow-the-ball panning in sports.
To me, the idea of (sports in) HD is that they give me a wider view,
and my eyeballs do the panning and scanning. There is enough detail.
> however I don't think I have ever come across even one
> DVD that has truly been encoded with "Pan-and-Scan" metadata.
> All widescreen DVDs I play on my 4:3 television, with pan-and-scan selected
> in the DVD player, always provides a 4:3 center cut, and that's all.
That's what I think too. Not that I ever watch on a 4:3 TV anymore...
> For that matter, I don't think I have ever come across a DVD encoded
> with multiple scenes, either.
If you mean "multiple angles", there are plenty of examples of that,
only they are not recognized as such. For example, in many Disney animated
movies, if they show a text or something, then depending on the language
that you have selected you get to see that text in your own language.
The "angle" is then a scene that is created specifically for a country.
> And we have the example like this Wizard of Oz release that deliberately
> disables pan-and-scan and viewer controlled zoom functions, because the
> content creator wants complete and total control over how his/her original
> concepts are presented.
There *are* no zoom controls for 16:9 content on a 16:9 display.
If they had put a real 4:3 movie on the BluRay disc, then you
might have had a choice of how to view it on a 16:9 display:
with side pillars or full-width and vertically cropped to 75%.
But as 4:3 HDTV on BluRay does not exist, the producer has already
made the choice for you: side pillars.
If you find it logical that a 16:9 TV can crop off the letterbox bars
(from a 16:9 movie in a 4:3 format), then it is also logical that a 4:3
(HD)TV can crop off the side pillars (from a 4:3 movie in a 16:9 format).
I wish you all good luck in finding a 4:3 HDTV, let alone one that has
been designed with a horizontal cropping option. Yes, a PC could do it.
By the way, my "Goofy movie" DVD was advertized on the box as true 4:3,
but it is actually a 16:9 movie letterboxed to 4:3. This explains why
I could see it as 16:9 or 21:9 (by using "movie expand"). I still have
to figure out why the same trick did not work with the BluRay player.
> If studios can't be bothered to encode simple scene-by-scene pan-and-scan
> metadata into DVD releases, why would they spend the extra time encoding
> scene-by-scene pan-scan-zoom information for multiple display sizes?
Because I think that the problem of incompatibility between SD and HD
formats (add even smaller portable screen formats) is far greater than the
incompatibility between SD 4:3 and SD 16:9 formats. Screen sizes now vary
from 2" to 150", and aspect ratios from portrait to super wide screen.
If a content provider wants a single content to look good on a variety of
screen sizes and aspect ratios, then it may be inevitable that the content
be re-targeted for each receiver for its specific screen format.
And this is far easier to do with some intelligent metadata than having
to guess (..shudder..) the area of interest from the image content alone.
For every frame, send the top-bottom-left-right co-ordinates for the
box that contains the important action. The smaller screens show only the
content of that box. The larger screens can show more area around the box,
and the largest screens show the entire image. If the director thinks that
you should see the entire frame (for the purpose of telling the story),
then the box is the entire frame, or the largest 4:3 box at the best
position in the frame. The latter is a case of pan-and-scan, of course.
To Kilroy: does this help with your ideas ?
Groeten,
-- Jeroen
Jeroen H. Stessen
Specialist Picture Quality
Philips Consumer Lifestyle
Advanced Technology (Eindhoven)
High Tech Campus 37 - room 8.042
5656 AE Eindhoven - Nederland
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