Re: [SLUG] video capture card

From: Derek Glidden (dglidden@illusionary.com)
Date: Wed Apr 10 2002 - 11:20:52 EDT


On Tue, 2002-04-09 at 22:56, Paul M Foster wrote:

> I've seen one major disadvantage of not letting Tivo phone home (the
> Tivo service): clock drift. The Tivo is a little computer, and its time
> will drift if it's not allowed to sync with the home office. I've also
> noticed that, if you don't let it phone home, after a while, it will
> lose future scheduled recording dates. However, cancelling and resetting
> just one of them will reset the future schedules for them all. Peculiar
> bug I haven't fully tracked down.

You also won't be getting software upgrades. If you're running the 2.0
version of the TiVo software, though, I'd recommend not upgrading. I
liked it better than the 2.5 that is currently on my TiVo. That's one
downside - I'd love to be able to tell the unit to downgrade itself to a
previous version. I can understand why the service wouldn't want that
though - support nightmares if everyone were running different versions.

The biggest advantage, for me, of the TiVo *is* the service, though. I
LOVE not having to dig through TV listings to find the shows I want to
watch. I just click the "search by name" option, put the show title in,
then click "record" and don't worry about when it's going to record it.

That, and the ability to do "Season Passes" where the TiVo will find any
time any channel a particular show is on and record it for you, are
worth the $9.95/mo for me. Except that it's going up to $12.95/mo
sometime soon. It's still worth it. (There's also the $100/yr and
$200/lifetime options, but I've stuck with the monthly for now.)

> Anyway, I'm interested in setting up a Tivo-like device on a regular
> computer. If anyone does it, I'd like to know more about it. A couple of
> unknowns I see are how you get the software to know what the channels
> are and then change them on time. And how do you compare such a system
> with a 19" - 36" television? Viewing programs on a 15" or 17" computer
> screen seems like it wouldn't be a lot of fun. And how do you connect it
> to a cable box or VCR, etc?

I've been working on this on-and-off for a few months now, so I've got
plenty of experience.

If you're willing to choke down having a Windows box do all the hard
work for you, there are two pieces of software out there: ShowShifter
and SnapStream. ShowShifter looks and acts more like TiVo and you watch
the shows directly inside of ShowShifter, where SnapStream has a goofy
web-based interface to do the recording and need to use Media Player to
watch anything. ShowShifter is still under active development where you
download weekly (or so) beta versions to install over the version you
are currently using, where SnapStream is more shrinkwrap with "clean"
1.0 and 2.0 releases. They're both awkward, but ShowShifter is a little
more intuitive as a PVR application. Of course they're both commercial,
and you're just about better off just buying a TiVo, since it'll work
much better.

There are many other half-assed attempts at PVR software under windows,
usually stuff that gets bundled with video capture and tuner cards.
Mostly they just act like an AVI/Windows Media recorder that you
manually tune a channel and click the "record" button. ATI supposedly
has some fancier PVR type application bundled with their new Radeon
cards, and Happauge has a whole line of capture cards, including an
MPEG-encoding box specifically designed to be PVR hardware (costs $300
of course) with its own software. All of this stuff runs under Windows
as well.

As far as anything that runs under Linux, there are not many options.
There is a piece of software called 'vcr' that more or less works, but,
like everything else along these lines under Linux, requires a lot of
bleeding-edge libraries. I've been able to get vcr to work on occasion,
but mostly it has problems recording or, it will record something, but
then the format it's decided on its own to record is something I can't
play. (it uses the avifile stuff, which is a linux layer on top of
windows AVI DLLs, so is flaky at best.)

The closest thing I've been able to get working is the "mjpeg-tools"
that are built to work with the BTTV drivers. If you're lucky enough to
have a supported card with MJPEG in the hardware, you can use the tools
to change channels and record things and encode with MJPEG hardware
support. If you just have a normal TV tuner card with no hardware, you
can do software MJPEG, but expect to need something in the neighborhood
of a 1Ghz Athlon to get 30fps at 1/2 TV resolution. Playback of MJPEG
compressed files can be done with Heroine Virtual's "xmovie" software.

Then there's the Linux DVR stuff that was announced on Slashdot the
other day. Unfortunately, it ONLY works with a specific chipset of
digital tuner card that is mostly used in Europe and a very few places
in North America, so is almost entirely useless for us Yanks. I imagine
with some Slashdot exposure, though, someone will probably hack into it
to make it support a wider range of cards.

The biggest problem under Linux is that full Broadcast Quality recording
(30fps, ~640x480) REQUIRES hardware compression. I've tried various
software encoders on my 1.33Ghz Athlon at home and the best I've been
able to do is about 60% CPU utilization at 1/2 broadcast resolution,
30fps, or about 8-12fps at broadcast resolution with 100% CPU
utilization. But when those 2.6Ghz Athlons are available, then maybe
software-only encoders will be feasable.

And of course, there are very few hardware encoding boards that are
supported under Linux. The Happauge WinPVR card has someone attempting
to write drivers for it but at the moment, all he has working is the TV
tuner part, not any of the encoding stuff. The Iomega Buz and related
cards that use the same chipset have a driver and are supported with the
mjpeg-tools, but lack a TV tuner - they're only video-in cards.

Unfortunately, in the current regime of DMCA and SSSCA and the RIAA and
MPAA suing the pants off of anyone and everyone who looks like they
might have something to do with possibly allowing the end-users to do
anything other than what the studios absolutely demand be allowed for
broadcast media, it's unlikely that anyone is going to make a PVR type
card with available Linux drivers. It's too close to saying "This card
can be programmed to do whatever you want, therefore it can be seen as
violating the DMCA as a 'circumvention device'" and they'll get sued
into oblivion. So for now, you'll probably only ever see Windows-based
hardware that supports all the crappy Windows Media rights control stuff
that keeps you from doing what you wanted the thing to do in the first
place.

Personally, I'd seriously consider the Sonicblue ReplayTV. The new 4000
series has the ability to stream programs from one unit to another, and
the protocol used has been reverse-engineered, so there is software out
there that will let you stream a program from a ReplayTV unit into a
local MPEG player on your computer, which is really the main reason *I*
would want a computer-based PVR - so I can archive the shows I really
enjoy.

-- 
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
#!/usr/bin/perl -w
$_='while(read+STDIN,$_,2048){$a=29;$b=73;$c=142;$t=255;@t=map
{$_%16or$t^=$c^=($m=(11,10,116,100,11,122,20,100)[$_/16%8])&110;
$t^=(72,@z=(64,72,$a^=12*($_%16-2?0:$m&17)),$b^=$_%64?12:0,@z)
[$_%8]}(16..271);if((@a=unx"C*",$_)[20]&48){$h=5;$_=unxb24,join
"",@b=map{xB8,unxb8,chr($_^$a[--$h+84])}@ARGV;s/...$/1$&/;$d=
unxV,xb25,$_;$e=256|(ord$b[4])<<9|ord$b[3];$d=$d>>8^($f=$t&($d
>>12^$d>>4^$d^$d/8))<<17,$e=$e>>8^($t&($g=($q=$e>>14&7^$e)^$q*
8^$q<<6))<<9,$_=$t[$_]^(($h>>=8)+=$f+(~$g&$t))for@a[128..$#a]}
print+x"C*",@a}';s/x/pack+/g;eval 

usage: qrpff 153 2 8 105 225 < /mnt/dvd/VOB_FILENAME \ | extract_mpeg2 | mpeg2dec -

http://www.cs.cmu.edu/~dst/DeCSS/Gallery/ http://www.eff.org/ http://www.anti-dmca.org/



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