----- "Hans Verkuil" <[email protected]> wrote: > On Monday 18 January 2010 19:42:45 Devin Heitmueller wrote: > > On Mon, Jan 18, 2010 at 1:35 PM, Hans Verkuil <[email protected]> wrote: > > > - NTSC and WSS. I still do not know how NTSC determines whether the > > > source is > > > 4x3 or 16x9. PAL uses the WideScreen Signal (WSS). A similar feature > > > exists > > > for NTSC, but it is unclear whether it is actually used by broadcasters. > > > Nobody seems to know. > > > > The reality is that for NTSC there is no standard. There is an NTSC > > variant of WSS discussed in the WSS specification, as well as a way of > > representing the info in EIA-608. As far as I have been able to > > gather though, neither have actually ever been used in production. If > > someone wants to offer some evidence to the contrary, I would be happy > > to add the support to tvtime and test it with some of my tuner boards > > (and fix any bugs that in the driver I find). > > Does that mean that you have to adjust your TV every time the format > changes!? > > Usually when I am in the US and watch TV in my hotel room the picture is > always distorted. I really hope that is not normal behavior for NTSC and > widescreen TVs.
The *actual* reality is that an NTSC signal has an inherent *signal* aspect of 4:3. If you're looking at it off a composite cable, or a cable/OTA tuner you can force 4:3. The *image* aspect may be different: wider aspects are generally accomplished by letterboxing, though some consumer camcorders will record a 16:9 image as a 4:3 signal by doing an anamorphic squeeze of the video image. If it came in from a digital source, like a DTV tuner, things are murkier. I *assume* there's an aspect flag, and I assume tuners will set it, but both of these issues should be orthogonal to IVTV, I think, cause we're only concerned with composite NTSC and OTA RF NTSC-M, and you can safely force 4:3 on both. This is my technical understanding based on 20 years of making and editing the stuff; if anyone has a counterexample concerning broadcast or composite transmission that I haven't already noted, bring citations. :-) Cheers, -- jra -- Jay R. Ashworth Baylink [email protected] Designer The Things I Think RFC 2100 Ashworth & Associates http://baylink.pitas.com '87 e24 St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274 Start a man a fire, and he'll be warm all night. Set a man on fire, and he'll be warm for the rest of his life. _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
