All the TV tuner cards in the market can display subtitles, but don't
record them. I emailed ATI, Pinnacle, and others. None of their
tuner cards can do that. But even the old day VCR can record TV
closed-caption.
ATI had their old All In Wonder cards that do that. But their new TV
tuner cards just came out - 600USB or 650 PCI Express - don't have
this function.
I say people who have a need for closed caption should boycott these
TV tuner cards until they implement this function.
All all the tv tuner card manufacturers should take a look at this
post.
I took your question, as kind of a "dare"
First step, was to do a quick check of the datasheet for a capture chip.
I was all set to give a lecture about how "it would never work", when
what do I find in the spec sheet, but that it is supported. More
evidence piled up as I went along.
I have a WinTV GO-FM card. That is based on a BT878 chip. So I looked
in the copy of the BT878 spec I had, and discovered that the BT878 can
handle something like five different DMA targets. One of those is for
"Line 21", which in North America is used for Closed Caption.
So the cheap and cheerful BT878 has the ability to copy information
which happens during the Vertical Blanking Interval. Line 21 hides
off the screen. But the hardware knows of the importance of CC or
Teletext, so they put in a function like that, to get at the data.
Other tool flows seem to know about Line 21 as well. Graphedit is a
Microsoft tool for planning and setting up toolchains for video. The
program allows a designer to hook together filters and codecs, to
playback content. The tool is graphical. Now, I found a picture of
someone's Graphedit setup, and they had a source box with a Line 21
output on it, and Microsoft has a filter that deals with Line 21.
Which means there is the ability to access Line 21 in a major design
package.
Things I wasn't able to research very well, was how CC might be
stored inside a movie.
So, to test all this out, I took the WinTV GO-FM, which was sitting
in one of my unused computers, and put it in my current computer.
First step, was to try the Hauppauge Windows software. I got the
latest software off their site. I think I was able to view
Closed Captions, but was not able to record them. Exactly as
you reported. But that doesn't mean that at the driver level,
Line 21 is cut off. It might still be there, waiting for
some Windows capture program to use it.
Since I wanted to do this little test, with zero budget, that meant
finding a free software route. I found some references to MythTV as
having the ability to record Closed Captions with the TV program.
First step, was to install Ubuntu. That wasn't too difficult, all things
considered. I've done a couple of these, for other OSes (FreeBSD,
Fedora), so have a bit of practice. My first mistake was updating
the graphics driver for my ATI video card. While the "tainted" ATI
driver might be useful for some other purposes, in this case it
actually seemed to work against the project. So that was a mis-step
that cost me some time. Also, a step I didn't do, was to install
on top of a "big file capable" filesystem. Apparently, there is
a file system recommended for use with MythTV, that is not used
by Ubuntu by default.
Using the latest Ubuntu, for a change, the package manager just worked
out of the box. You use the Synaptic Package Manager, to download and
install software not included with the original CD you make. By
selecting MythTV, it drags down all the software needed to make the
project work.
Now, at this point, I'd like to say, that a person would have to be
very determined to get this stuff to all work. The instructions are
not step by step, and I only discovered how some of the stuff worked,
by trial and error. And some of my install is still broken (Program
Guide), and without that, it isn't really a PVR.
MythTV uses a database, for some reason. I still haven't figured out
what exactly it is storing in there. I did manage to find the
directory that holds the recorded TV programs, so didn't need to
investigate that part of it much further.
First, I ran the "mythtv" program, and it told me that all my tuners
were busy. I knew that meant, that no tuners had been defined, but
the error message didn't say that.
Next, after wasting more hours on it, I discovered there is a
"mythtv-setup" program. That at least allowed me to declare a
tuner/capture card. But I was still getting the same errors from
"mythtv" when I ran it.
I found that the "scantv" program would work, so at least I could
tell that the BTTV driver system that was installed automatically
during the Ubuntu install, was working a bit. It meant that the
software could see the capture card, and work the tuner.
Eventually, I discovered that a simple label dialog (i.e. give the
capture card a name) was the missing step. Once that was done, then
the "mythtv" program stopped pestering me that no tuners were available.
The automatic channel scan, defines the available channels, of which I
could pick up about 8 channels or so.
OK, now I had video on the screen, but no sound. The WinTV-GO has a
cable, that runs from the capture card (Line-out), to the sound card
(Line-in). The MythTV software defaults to defining /dev/dsp as the
source of sound, but my capture card has no ability to record audio
directly (so /dev/dsp has nothing to offer).
I discovered I had a program called "alsamixer", and by using that,
could play with the sound card.
One little trick, is my TV capture card doesn't really stop running
entirely, when MythTV exits. So I know there is a sound signal
still valid and working on the output, after you stop using it.
(Rebooting the computer, stops it.)
I tried the following, to test for sound coming from the capture
card (outside MythTV). This would only apply to how my WinTV card
does the audio.
arecord | aplay
What that does, is record sound samples from a sound card input,
and pipe the samples to the sound card output (the green Lineout
connector, and my two computer speakers). By using that command
in one terminal window, and playing with the alsamixer, I was able
to get sound through the speakers.
But I still couldn't get sound in MythTV. It turned out that
instead of /dev/dsp, I was supposed to use /dev/audio. Now
I had sound.
What remained, was getting Closed Captions to work.
Pressing the letter "M", brings up the on-screen menu, in
"mythtv". There is a setting there, to enable CC. I selected
CC1 and tuned a French channel in my viewing area. It has
Closed Captions for their program content. Now I could
see CC on the screen.
I pressed the "R" key, to record the content. I still don't
really know what stops the recording from being made. I figured
it might be the "S" key, but I'm not sure. There is no onscreen
feedback about the recording state of the program. I had at
least one case, where recording was still going on after I exited
MythTV. I'm sure there is some method to their madness, but
I haven't figured it out yet.
The breakthrough was about an hour ago. I used a command like:
mythtv 1007_20071105042128.nuv
to play back a recorded program segment, from the French channel.
By bringing up the on-screen menu again, with the "M" key, you
have to select a Closed Caption option in the playback screen,
to get the Closed Caption to appear. Success! I could see
Closed Captions coming from the recorded .nuv file.
There are still lots of things I don't understand about the
whole thing. With no Program Guide, I cannot actually set it
up to record anything automatically, and prove it is a fully
working solution. There is a window that pops up, and in
the window is a dialog full of lines of text, where the
MythTV program tries to talk to a Program Guide web site.
But the window closes and disappears, before I can do anything.
Since it goes by too quickly to make any notes, I don't know
what setting it is trying to use, and how to fix it.
Apparently, there are also tools for extracting the CC content,
and post-processing it. I haven't got any of that to work
either.
So, I was able to get one solution to work, in a very limited
way. It can be done.
"SageTV - Recording Closed Captions"
http://forums.freytechnologies.com/forums/showthread.php?postid=44757#post44757
"SageTV Who wants CC?"
http://forums.freytechnologies.com/forums/showthread.php?t=5308&page=5
Reply #9 on: November 20, 2005, 08:49:11 AM "Closed Caption Capture"
(Explains problems the programmers have. "VBI Pin scheme" refers to
GraphEdit and accessing Line21 in a MS environment.)
http://forum.byopvr.com/dvr/index.php/topic,392.0.html
(Claims to extract CC from the MythTV files)
http://ccextractor.sourceforge.net/
(Some details on converting MythTV files to other forms.
I couldn't get mplayer to work, so I'm not making any progress there.)
http://www.linuxjournal.com/article/8524
None of this is for the faint-hearted.,,
Tis a huge time waster...
If the Windows programmers looked at how MythTV handles it, I think
they might be able to come up with a similar solution.
HTH,
Paul
