> Date: Mon, 18 Jan 2010 13:42:45 -0500
> From: Devin Heitmueller <[email protected]>
> 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 broadcast count, or just NTSC from a DVD player?
In particular, I have a 10ish-year-old Sony WEGA SDTV. It has a mode
(which I leave enabled) that can autodetect the signal coming from a
widescreen DVD in a DVD player, and will do an anamorphic squeeze to
preserve vertical resolution (effectively putting all the scanlines in
less vertical real estate and letterboxing the display by failing to
scan the top and bottom at all). It gives me really sharp widescreen.
It detects the presence or absence of the signal in a few hundred ms
at most and makes a visible change in scan mode.
This signal is clearly being transmitted in the NTSC signal, since it
works via component, composite, or S-Video. I can even record it onto
a VHS videocassette and play that back and it works.
However, when I tried this very early on with MythTV and ivtv 0.4.1
(feeding the DVD's output into Myth), it didn't work. Capture was
from a PVR-250 or -350 and playback through a -350. I -do- have these
lines for each tuner which run on every boot:
/usr/local/bin/ivtvctl -b wss,cc -x 1 -d /dev/video0
/usr/local/bin/ivtvctl -b wss,cc -x 1 -d /dev/video1
...
and for the -350:
/usr/local/bin/ivtvctl -w wss,cc -d /dev/video0
I never tracked down whether it was the encoder, the decoder, or both
that didn't work. I do still run all this hardware, but (if it matters)
I won't be able to test anything that involves newer ivtv versions until
a few months from now (when I decommission the -350 and can put it in a
machine I'm not holding absolutely stable). FWIW, closed captioning
does work, both in decoding and encoding.
I've also never seen it used by a movie channel, even when I used to
watch and/or record movies via completely analog signal paths (e.g.,
RF broadcast, or cable, direct to the TV or to VHS), so if broadcasters
do use this, I haven't happened to see it.
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