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[ivtv-users] ivtv TODO list

 

 

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f-myth-users at media

Jan 18, 2010, 5:34 PM

Post #1 of 5 (2327 views)
Permalink
[ivtv-users] ivtv TODO list

> 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.

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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hverkuil at xs4all

Jan 18, 2010, 11:28 PM

Post #2 of 5 (2190 views)
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Re: [ivtv-users] ivtv TODO list [In reply to]

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?

Both count.

> 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?

Regards,

Hans

> 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
> http://ivtvdriver.org/mailman/listinfo/ivtv-devel
>

--
Hans Verkuil - video4linux developer - sponsored by TANDBERG

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f-myth-users at media

Jan 18, 2010, 11:52 PM

Post #3 of 5 (2182 views)
Permalink
[ivtv-users] ivtv TODO list [In reply to]

> Date: Tue, 19 Jan 2010 08:28:17 +0100
> From: Hans Verkuil <hverkuil [at] xs4all>

> > 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?

Note, btw, that I do have extra 250 hardware and expect to have a
machine available within days on which I'll be running Ubuntu 9.10
(and possibly something even more bleeding-edge if it would help).
So if only the 250 side of the equation needs work, I could test
using that and the 350 in another machine that's still on ivtv 0.4.1.
But I only have one 350 and the machine it's in is in constant use;
I can't make any potentially-destabilizing changes to that machine
until I decommission the 350, which probably won't happen until
midyear.

[.If anyone else has a spare 350 kicking around that they'd like to
send me, I can put -that- in my test machine and do all the testing
right now. Contact me offlist if so. There are probably quite a
number of people on the main MythTV lists who now have extra 350's
gathering dust, but I'm leery of asking that population directly.]

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f-myth-users at media

Jan 19, 2010, 12:15 AM

Post #4 of 5 (2192 views)
Permalink
[ivtv-users] ivtv TODO list [In reply to]

> Date: Mon, 18 Jan 2010 19:35:48 +0100
> From: Hans Verkuil <hverkuil [at] xs4all>

> - Currently a private 'ivtv' format is used to store VBI data in an MPEG stream.
> I know that there is a standard format that can be used to store info like
> this in an MPEG stream and that should make this more compatible.

This would be lovely. The current state of affairs means that doing
any sort of editing (such as removing commercials) loses all CC data,
since the tools that do so don't know to keep them. Only editors that
simply bulk-copy data between cutpoints keep anything, but most seem
to reencode the stream as it goes by (after all, you'd like to allow
cutpoints between GOPs and/or not simply chop half a frame off or
whatever), and thus CC gets tossed. Since I value CC data, this
means I can never edit. (Well, I can hook a 350's output to some
other card's input and do edits in the style of the bad old days
of tape-to-tape realtime editing, but that's not really what one
expects from editing these days... :)

> I know I
> looked at this in the past, but I decided against it at the time because the
> total size of the VBI payload could be more than the maximum size supported
> by the cx23415 MPEG decoder. It's not a problem to write larger packets, but
> the MPEG hardware decoder will truncate it internally.

> In hindsight I should have gone with the standard anyway since I don't think
> this will be a problem in practice.

Would it be possible to buffer the data and write any spillover to the
next packet? (Better a late caption than half a caption.) This
assumes that the average rate is low enough that you won't require
indefinitely-large spill, of course. Though if you think that nobody
puts -that- much CC in any source anyway, the complexity wouldn't be
worth it.

If someone makes this change in CC embedding, it would also be
wonderful if ivtv included a tool that could take the old-style,
incompatible stream, and re-embed the CC data in a new stream in the
new, compatible style. This would allow previously-recorded streams
to be editable and would allow flushing out all the old-format data
in an archive all at once.

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nufan_wfk at yahoo

Feb 7, 2010, 7:38 PM

Post #5 of 5 (1889 views)
Permalink
Re: [ivtv-users] ivtv TODO list [In reply to]

I'll go on-list for this.

I have the original pvr350 used to develop the video-out stuff for ivtv available. I'd love to see it get used for further ivtv development

I've gone all DVB (clearQAM and ATSC) now, so my SD stuff is not being used much.

Caveat is the pvr350 has a shot tuner (i've had several pvr-x50's do this to me over the years, not sure what the problem is). The direct video input works fine. Remote works fine.

Video out is assumed to work, but i haven't used it in like 3 years :)

Thanks for all the help over the years guys. It's been fun being a part of it.

-tmk

--- On Mon, 1/18/10, f-myth-users [at] media <f-myth-users [at] media> wrote:

> From: f-myth-users [at] media <f-myth-users [at] media>
> Subject: [ivtv-devel] [ivtv-users] ivtv TODO list
> To: ivtv-devel [at] ivtvdriver, ivtv-users [at] ivtvdriver
> Date: Monday, January 18, 2010, 11:52 PM
>     > Date: Tue, 19 Jan
> 2010 08:28:17 +0100
>     > From: Hans Verkuil <hverkuil [at] xs4all>
>
>     > > 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?
>
> Note, btw, that I do have extra 250 hardware and expect to
> have a
> machine available within days on which I'll be running
> Ubuntu 9.10
> (and possibly something even more bleeding-edge if it would
> help).
> So if only the 250 side of the equation needs work, I could
> test
> using that and the 350 in another machine that's still on
> ivtv 0.4.1.
> But I only have one 350 and the machine it's in is in
> constant use;
> I can't make any potentially-destabilizing changes to that
> machine
> until I decommission the 350, which probably won't happen
> until
> midyear.
>
> [.If anyone else has a spare 350 kicking around that they'd
> like to
> send me, I can put -that- in my test machine and do all the
> testing
> right now.  Contact me offlist if so.  There are
> probably quite a
> number of people on the main MythTV lists who now have
> extra 350's
> gathering dust, but I'm leery of asking that population
> directly.]
>
> _______________________________________________
> ivtv-devel mailing list
> ivtv-devel [at] ivtvdriver
> http://ivtvdriver.org/mailman/listinfo/ivtv-devel
>




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