Accessible tv tuners from the cli?

Thu Oct 27 01:06:01 EDT 2011

Thanks, Bob, for all this good info. I'm not looking to do this myself
just now for a number of reasons, but I'm keeping your post against the
day I do want to do this.

Question: Isn't it worth considering simply accessing the content you
want over the net using a browser? Perhaps with a service like hulu.com
which is supposedly quite accessible. The famous name in this space, of
course, it Net Flix, but they're supposedly not so accessible.

I'd love to hear a discussion of the pros and cons of such services. I
am personally of the opinion that the future of broadcasting is the web,
not in the least because it's fully international and intrinsically
time-shift capable.

Janina

pigiron at gmx.com writes:
> On Wed, 26 Oct 2011 17:19:59 -0600 "Littlefield, Tyler" <tyler at tysdomain.com>
> wrote:
> 
> > Hello all:
> > I was curious if any of you have tried using a TV tuner from the cli? 
> > How accessible or otherwise was it? I'm building a computer hopefully 
> > soon, and would like to throw in a tuner, but I don't know how it'd work 
> > with speakup or if there's an accessible program to interface with them.
> > 
> 
> While I'm sighted, I run everything for my TV tuner from the command line
> except for post editing any recorded shows. But there's even some simple CLI
> video editors. I've never used them, so I can't speak to those.
> 
> Getting everything set up correctly is definitely a head scratcher though. So
> set aside gobs of time and get your zen in shape in order to keep your blood
> pressure in check.
> 
> It all starts with getting a TV tuner that Linux likes. I strongly suggest that
> you buy one that the Video4Linux, otherwise known as "V4L", Linux kernel
> subsystem supports. A good place to start is this web site:
> 
> http://www.linuxtv.org/wiki/index.php/Hardware_Device_Information
> 
> Like most Linux documentation, it's only slightly out of date; chuckle.
> 
> While you may find drivers and applications for non-V4L supported tuners on the
> internet, you'll probably find that they are old, or not maintained, or both.
> All the current action is on the V4L code, and it's been that way for awhile
> now.
> 
> You did not say which country you live in, nor which types of signals you'll be
> trying to watch or capture. That will make big a difference for some of the
> following information, along with which TV tuner you buy.
> 
> One of the first puzzlers you'll encounter is all the strange new buzz words.
> One is the anagram "DVB". I means Digital Video Broadcast, which differentiates
> it from the old analog broadcasts and tuners. Then you'll hit things like the
> words "DVB-C", "DVB-S", and "DVB-T". It took me awhile to figure out that the
> letter "C" means cable. The letter "S" means satellite. And the letter "T" means
> terrestrial; which is the over the air signal. You'll sometimes see that
> shortened to the anagram "OTA". Confused yet?
> 
> After you've slogged through all that, and figured out which tuner to buy, you
> install it and verify that Linux likes it by checking the output of the dmesg
> command. You should also now have files and directories located under
> the /dev/dvb directory.
> 
> If you get this far, you next need to create what's called a "channels" file.
> This is simply a strangely formatted text file that contains all the TV channels
> that the tuner finds in your local area. It's analogous to scanning the
> available channels on one of those new fangled digital televisions.
> 
> There are multiple command line programs that will create the "channels" file.
> Which one you use partially depends on what type of signal you want to capture;
> such as cable, satellite, or terrestrial; along with which country you live in.
> Drill down from this web page for more info:
> 
> http://www.linuxtv.org/wiki/index.php/Frequency_scan
> 
> After you've successfully scanned the TV channels for your area and created the
> "channels" file, you'll find that you probably need copy that sucker into
> multiple directories. The mplayer program expects to find it in one place,
> while the xine player expects it in another, and so on. But once you get in
> place, you can now tell the player which TV channel to play by using it's name.
> For example, if you want to play a station called "WCBS" using the mplayer
> application you could enter the following:
> 
> mplayer tv://WCBS
> 
> But, how do you know what station name to use??? The answer is to look inside
> that strangely formatted "channels" text file you created. Each line is a
> different channel, and the first field is the TV station name. Each field
> within a line is separated by the colon character. It's safe to edit the
> channel file and change those TV station names to something you like. But, do
> not change any other field on a line.
> 
> Note that mplayer normally spews a ton of output to the terminal, you may
> want to try the "-really-quiet" parameter to keep the output from speakup to
> a minimum, or turn it off.
> 
> If you wish to capture a show, just one simple way to do it from the command
> line is to bring up a terminal and use one of the "zap" programs provided in
> the "dvb-apps" package to tune your tuner to the particular TV channel. Which
> "zap" program you use depends on the type of TV signal. See the following for
> more info:
> 
> http://www.linuxtv.org/wiki/index.php/Zap
> 
> Next, open another terminal and simply redirect the output of your tuner device
> to a file. For example, something like the following might work if you only
> have one TV tuner installed:
> 
> cat /dev/dvb/adapter0/dvr0 > testvideo.mpg
> 
> While that documentation states that the "zap" programs can also be used to
> record a program, the "azap" program that I use doesn't support it.
> 
> If you attempt to capture the new ATSC over the air digital HDTV channels now
> found in the USA, expect to eat up gigabytes of drive space. You'll find that
> the sucker is in the MPEG Transport Stream format, and unless you live next
> door to the transmitter, it will also contain errors. While mplayer and VLC
> among others, will play the file, if you want to convert it into a DVD format,
> you'll need to fix all those errors. I'll leave those numerous painful hints
> for some other time.
> 
> I found a really obscure command line program from a bloke in Australia that
> will set up a timed recording, but I had to modify the hell out his C language
> program. For one thing, he has the channels hard coded; ouch! But here's a link
> if you're looking for even further frustrations:
> 
> http://www.togaware.com/linux/survivor/TV_Recording.html
> 
> You simply tell it which channel to record, the output file name, what time to
> start recording, and when to stop. Kind of like a DVR.
> 
> I could go on forever, but I've bored you enough. Hope this helps, and good
> luck.
> 
> peace,
> bob
> _______________________________________________
> Speakup mailing list
> Speakup at braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup

-- 

Janina Sajka,	Phone:	+1.443.300.2200
		sip:janina at asterisk.rednote.net

Chair, Open Accessibility	janina at a11y.org	
Linux Foundation		http://a11y.org

Chair, Protocols & Formats
Web Accessibility Initiative	http://www.w3.org/wai/pf
World Wide Web Consortium (W3C)