hverkuil at xs4all
Jan 18, 2010, 11:28 PM
Post #2 of 5
On Tuesday 19 January 2010 02:34:33 f-myth-users [at] media wrote:
> > Date: Mon, 18 Jan 2010 13:42:45 -0500
> > From: Devin Heitmueller <dheitmueller [at] kernellabs>
> > On Mon, Jan 18, 2010 at 1:35 PM, Hans Verkuil <hverkuil [at] xs4all> 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.
This sounds very much like this TV actually implements the NTSC WSS signal.
> 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
Currently wss is only supported for PAL/SECAM and not for NTSC. But this
sounds like an ideal test case to add wss support for NTSC and test it.
> 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.
Does anyone else have similar behaving TVs & DVD players and is willing to
test with newer ivtv versions?
> 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.
> ivtv-devel mailing list
> ivtv-devel [at] ivtvdriver
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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