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Posted by Lincoln Spector on 12/06/06 17:54
Look, you're plainly more up on this stuff technically than I am.
I used the computer example as proof (a proof that everyone in this group
has probably seen) that the flag exists.
I don't know what the standard is, but here in North America, there
obviously IS a standard that allows DVD players to tell TVs that it's a
widescreen image. My DVD player and TV are from different companies, and it
knows.
Here's an interesting fact: When I switch inputs, the TV gives me tech specs
on the new input. For the VCR (coaxial cable connection, DirectTV Tivo
(S-Video), and LaserDisc player (composite video), it says NTFS--the
American TV standard. For the DVD player, it says either 720x480 4x3 or
720x480 16x9.
Lincoln
"Jukka Aho" <jukka.aho@iki.fi> wrote in message
news:4Qzdh.954$kD4.560@reader1.news.saunalahti.fi...
> Lincoln Spector wrote:
>
>> Part of the DVD signal identifies the program as 4x3 or 16x9. Ever
>> watch DVDs on a computer in a window (as opposed to full-screen). The
>> window changes shape when it goes to 16x9.
>
> Of course, but that's beside the point. The aspect ratio switching works
> on a computer screen because the (software-based implementation of a) DVD
> player on a computer can directly read the aspect ratio flags off the
> original MPEG-2 stream. The situation is different when you're watching
> DVDs using a set-top DVD player and a regular tv set. The tv set does not
> have any direct access to the original MPEG-2 stream, much less to the
> aspect ratio flags within that stream. Only the DVD player has access to
> that information.
>
> It is possible to relay the aspect information from a set-top DVD player
> to the tv set - and that is indeed what is being done in 625/50 countries.
> For that to work, however, you need an aspect ratio signaling
> specification: some sort of standard that is universally agreed upon among
> DVD player manufacturers and tv manufacturers.
>
> Two such widescreen signaling standards have been devised for the 625/50
> system. Both are widely used in the PAL countries. But neither of these
> methods is directly applicable to the 525/60 ("NTSC") signals.
>
> What I'm interested in, and what my original question was about, is
> whether there are similar (widely-used and widely-supported) widescreen
> signaling standards for the 525/60 world - and if so, how do they work,
> and where are they specified.
>
>> Whether that information gets to the TV, I'd imagine, depends on what
>> type of connection you're using. I'm using component video, and it
>> works fine. I suspect it also works with HDMI and doesn't work with
>> composite video. I don't know about S-Video.
>
> Not necessarily. For example, the line 23 ("PALplus") widescreen
> signaling - which is one of the methods used in 625/50 countries - is
> designed in such way that it survives all commonly-used analog signal
> types - CVBS, Y/C, YPbPr, RGB. It even survives recording onto a VHS tape.
> (The VHS VCR does not need to support this in any special way.)
>
> Now that I scoured the web, it seems that there actually _is_ a
> specifically tailored version of the PALplus line 23 WSS signaling for the
> 525/60 systems. It carries the same information, albeit on different lines
> (20 and 283.) See this Intersil application note (page 3):
>
> <http://www.intersil.com/data/an/an9716.pdf>
>
> Without further investigation, it is hard to say whether this is the exact
> WSS method that is being employed when you're watching DVDs using your
> set-top player, but it would seem plausible. If it is, I would expect the
> aspect ratio signaling to work on the same equipment even over composite
> video (yellow RCA) connections.
>
>> You also have to tell your DVD player that you have a widescreen TV
>> (there's a setting in there somewhere). Without telling it that, the
>> player will convert all 16x9 signals to 4x3, adding letterboxing and
>> reducing the vertical resolution by 25%.
>
> It's the same over here in 625/50 land, but that "16:9" setting is not
> strictly for 16:9 sets only. It's more like a "is your tv set capable of
> handling full-frame 16:9 signals all by itself?" setting.
>
> For example, I have a 4:3 SDTV set (a direct-view CRT) that can handle
> full-frame ("anamorphic") 16:9 signals just fine and display them in their
> correct aspect ratio - letterboxed within the 4:3 screen. Hence, I'm using
> a "16:9" setting on my DVD player, even though it is not connected to a
> 16:9 set. (When that TV set encounters video that is signaled as being
> "16:9", it changes its vertical deflection sufficiently so that you'll get
> a letterbox effect. It still draws all the lines on the screen - just
> constrained in a tighter space. This way, you'll get at least marginally
> better resolution than when you let the DVD player do the letterboxing up
> front. The actual increase in resolution depends on a number of different
> factors, of course - such as the resolution of the shadow mask and the
> focusing of the electron beam.)
>
> --
> znark
>
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