Because of the way it works, it’s possible to take any input, and spit it out in any way pretty much. Some time ago I’d seen a discussion on a mailing list about using VLC and a digital TV card to broadcast live TV over the network (using multicast). I’d had a quick play, but never got it working. A discussion popped up on the Multiplay forums, so I thought I’d try and get it working again. Last night I was successful, so I thought I’d blog it up in case it’s useful for others. VLC is documented, but the documentation is a bit hit and miss in places – always the problem for many Open Source projects.

Read more after the jump.

Background

Digital TV, using either satellite (DVB-S) or terrestrial (DVB-T) is fundamentally the same – MPEG2 Transport Streams, which are multiplexed into one stream, then broadcast on a single frequency. The tuner will tune to the frequency, then pick the stream it wants, and play it on screen.

The idea behind what we’re doing here is to take that multiplex, and pick out the streams we want, then just multicast them as is onto the network. Using the SAP protocol, it’s possible to announce them in a nice neat way so clients can pick them up easily.

Because it’s already MPEG2, no re-encoding is really needed. I suppose you could do that, but I’ve not tried. This method uses hardly any CPU time, as it’s just pulling data in, patting it about a bit, and throwing it out the other side. In the original mailing list postings I read, the author was using some old Pentium 4 PCs with hardly any RAM. They were capable of tuning multiple channels with ease.

One caveat of this is that the tuner can only lock onto one frequency, so one multiplex is all you can play with; on Terrestrial (i.e. Freeview), the BBC multiplex contains all the BBC channels. If you wanted to multicast BBC and ITV channels for example, you’d need to add a second tuner and tune to the ITV multiplex.

In my investigations, I had the following setup:

Both are connected over a Gigabit network. However, the video streams are quite small (5-6Mb/s). Even 10Mb network could cope with that, although not many concurrently!

The server end

First of all, here’s the full command to kick start VLC on the Server.

vlc dvb-t://frequency=578000000 :adapter=0:dvb-bandwidth=8 --programs=4171,4235
--sout #duplicate{dst=std{access=udp,mux=ts,dst=239.255.255.239,sap,name="BBC One",
group="BBC"},select="program=4171",dst=std{access=udp,mux=ts,dst=239.255.255.238,
sap,name="BBC Two",group="BBC"},select="program=4235"

That’s all on one line, I had to break it up a bit!

So an explanation of it. Basically it runs VLC, tunes the frequency, using a selected adapter and channel bandwidth. It then selects the two programs I want (BBC One and Two), then outputs them via UDP on two different multicast addresses, using SAP to announce it.

First of all, I’d recommend running VLC up manually. Go to Media >Open Capture Device. Change the capture mode to DVB Directshow. Select the video format you’re using (I’m using DVB-T). Then dial in the frequency of the multiplex you want. Select 8Mhz for the bandwidth. You can find out the multiplex frequency using UKfree.tv.

Click Play, and it should open.

If it doesn’t you might need to select your video adapter explicitly. I have two in my PC. The DVB-T card is adapter 0, whilst my DVB-S card is adapter 1. Click Media > Open Capture Device again , then tick Show more options and enter “:adapter=0” into the options box. In the previous screenshot I have highlighted this. Change the number until it works.

Once you are able to see the video, go to Tools > Messages. Change the Verbosity to 2. Stop and start VLC and watch the log fill up. There’s too much to try and work with it in the window, so click Save as…. Open the file you have saved, and look for a section similar to the following:

ts debug: new SDT ts_id=4107 version=3 current_next=1 network_id=9018
ts debug:   * service id=4171 eit schedule=1 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=BBC ONE
main debug: EsOutProgramMeta: number=4171
ts debug:   * service id=4235 eit schedule=1 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=BBC TWO
main debug: EsOutProgramMeta: number=4235
ts debug:   * service id=4415 eit schedule=1 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=BBC NEWS
main debug: EsOutProgramMeta: number=4415
ts debug:   * service id=4479 eit schedule=0 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=BBC Red Button
main debug: EsOutProgramMeta: number=4479
ts debug:   * service id=4671 eit schedule=1 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=CBBC Channel
main debug: EsOutProgramMeta: number=4671
ts debug:   * service id=4351 eit schedule=1 present=1 running=4 free_ca=0
ts debug:     - type=1 provider=BBC name=BBC THREE
main debug: EsOutProgramMeta: number=4351

Notice all the Service IDs. As you can probably tell, each of these represents a TV channel within the multiplex. You need to note down the ones you want to multicast. In this case I want BBC One (4171) and BBC Two (4235).

The next part of the command selects those programs and outputs them:

--programs=4171,4235 --sout

The next part is to make up the multicast. As the video is already in MPEG2 we don’t need to go re-encoding it, so it’s simply a case of spitting it out.

I’ll be honest, I’m not sure what this next section does – I think it is basically saying take the input and duplicate it to output elsewhere (i.e. other than on screen).

#duplicate{

We are going to broadcast on a multicast address (anything in the range 224.0.0.0 to 239.255.255.255). You need to choose your addresses. On a large network with multicast enabled, these could be in use, so it’s worth checking first. If you know you don’t have any multicast I think it’s fairly safe to pick a random address. I chose 239.255.255.255.239 and went down from there!

This next line is where we select UDP, make it a Transport Stream, select the target IP, and advertise it with SAP. The channel name, and group name are set here too:

dst=std{access=udp,mux=ts,dst=239.255.255.239,sap, \
name="BBC One",group="BBC"},select="program=4171",

Repeat for BBC Two. Use a different multicast address though!

dst=std{access=udp,mux=ts,dst=239.255.255.238,sap, \
name="BBC Two",group="BBC"},select="program=4235"

Now we have a full command, it’s a case of running it. I used a command prompt and ran VLC from there, but you could of course put it into a shortcut, batch file, registry run key, or whatever.

Once it’s running, a very simple, hacky way of checking it is working is to look at your network switch. If it’s flashing away merrily on all ports, then it’s doing something!

The clients

Run VLC on another PC, Go into Preferences > Playlist > Services Discovery and tick SAP. You might need to re-start VLC. Go to the playlists, and you should see a group with the name you made, and your channels. Click one, it plays!

As you can see, I’m doing this on my Mac, so it’s truly cross platform!

I did find in testing that it caused an effective DoS on my Wireless. I’m guessing the multicast was too fast for the slowest wireless device associated to the AP, and just wiped the lot out or something. Wired carried on working fine though. Something to bear in mind anyway!

I’m sure it’s possible to refine this a little more. The original version of this I saw had VLC daemonizing itself, which I’m not entirely sure is possible in Windows. Still, it’s a great way to get video served up over the network.

Oh, and remember, you still need a TV licence!

Via some spare fibres and various spare switches, we’ve got access to it in various switch closets. I wanted to be able to access it from my desktop. My preference was to use a virtual machine, which I could set up with all the software I needed and test. This would mean bridging said virtual machine to that network.

I added a second network adapter to my PC, unbound it from all the local protocols (so my PC doesn’t touch that network) and set VMware Player to use bridged mode. With VMware workstation, you can use the virtual network tool to configure which NIC bridges to the virtual machines. However, that tool is missing with VMware player. By default, it was bridging to my first NIC, which was no good, as it was on the uni network.

A little bit of clicking around, and I found that there is a protocol bound to all the network cards called VMware Bridge Protocol. By default, it seems to bind itself to all the NICs. I simply unbound it from my main NIC:

And left it bound to the NIC connected to the ADSL network:

I restarted VMware Player, and my virtual machine nows bridges to the ADSL connection.

Post update, it decided to redirect me to google.nl all the time. No idea why, as it had been working fine previously. Checking every option I could within Opera, I could find no reason why.

The answer, lies in a config file, which lives here: (I’m on Windows 7, so yours may vary slightly)

C:\Users\<Your Username>\AppData\Roaming\Opera\Opera\operaprefs.ini

Towards the end of the UserPrefs section, is this line:

Google TLD Default=.google.nl

That was the one! I changed it to .co.uk, restarted Opera, et voila, it now goes where it’s meant to. I can only assume it’s something the installer did. My system is set to UK everything (I checked) and I’ve never had anything else go whizzing off to google.nl. Even going to google.com redirected properly.

Very odd!

Currently, according to most polls, Labour is mostly trailing. The Tories are slightly out in front, and the Lib Dems are mostly weaving up and down the polls. There’s lots of talk of a possible ‘hung parliament’. Personally, I can’t help but feel that it won’t happen. The Tories are edging slowly higher on a daily basis. They need around a hundred seats to take a majority. It’s possible it could happen, and each day seems more likely.

A hung parliament could be a good thing, as it could bring around a lot of reform people have often spoken of. Electoral reform would be a great thing, given that our local seat is ALWAYS Tory, and has been since 1926. The likelihood of him losing his seat is amazingly low. I don’t feel represented in parliament because of this. My vote is effectively useless, because the winning party represent an opposite view to my own. Some sort of reform could change that. I don’t think a hung parliament is likely though.

The notion of a Tory government being formed concerns me, given how dead-set they seem on hacking so much money out of the government budget. Right now is the wrong time. I just know they’ll sell the government stake in the banks off almost instantly. It’s too soon to do those things.

It’s right the budget is too high though. The BBC put together this useful infographic on spending. It’s a never-ending issue that the electorate want a government that doesn’t tax them, but spends massively on public services. Efficiencies can be found all over government. Hacking money out at the top isn’t going to work. It has to start within. Despite what many people will say, there’s plenty of career benefits claimants milking the system. I fully agree in a totally free healthcare, schools, and a social security system to help those that need it. Claiming benefits shouldn’t be a viable alternative to working. It should be there for those who find themselves out of work suddenly, or can’t work due to illness or whatever. Social security accounts for a massive slice of government money. It should be carefully reviewed and reduced.

When I went through school, it was mostly under the Tories. I remember schools being like something out of the latter years of Soviet Russia. Poor books, peeling paint, ripped curtains, broken furniture. Just before I left things were turning around a lot. Taxation on the richest parts of society brought in money to fix those things.

The Tories are planning to raise the threshold on Inheritance Tax. Well that’s good – if you’re in a tiny minority of people. They want to cut corporation tax. Even better. Now those big corporations can earn even more off us. Money we never see! So fatcat bosses can earn yet more off share options and dividends. More money they can hand over to their children in inheritances. At least it won’t be taxed!

Meanwhile, the lowest parts of society, those who need it, will find themselves unable to get benefits they need. The career benefit cheats will however continue to claim.

The thing is, it’s ordinary working class and middle class people voting in the Tories. Why, I don’t know. They only do things to benefit the rich. Privatisation only made a bunch of rich shareholders richer.

I don’t believe everything the Labour Party has done is right. The war in Iraq was stupid and pointless. The Digital Economy Bill was a whitewash. However, I feel that Labour offers a much, MUCH safer option in this post recession climate.

It feels to me that we’re heading towards some very bleak years.

On a similar note, today saw the English Defence League pay a visit to our little town. It passed off largely uneventfully. However, the comments bandied around on Twitter and the news articles on the Bucks Herald website leave me cold. There’s this hard core of ‘ordinary’ people who are convinced their liberties and laws are going to be replaced with some sort of radical Islamic legal system. I’m really not sure why. A local event is being held on Monday to claim the town back. It’s our town – everybody who lives here. We all live together quite happily, and don’t need anybody poking their oars in trying to incite trouble.

The thing about the call which intrigued me the most was that BT are notoriously bad at acting on changes of information. Indeed, somebody from BT told me that a lot of their billing hangs off company names and addresses, so changing it causes all sorts of headaches for the billing department – hence why they don’t!

I can’t help but feel my friend on the phone was cold calling from some random agency, basically looking to find info about us and what we do and needed, which they’d then cold call us about and try to sell to us. Maybe I was being over-cautious, and she was legit. I don’t know, and don’t care. Frankly BT, there’s much better ways of doing this!

To see them requires either a motorised/adjustable dish, or a second dish with a world of LNBs attached to it. I’ve already got a dish for Sky, and didn’t fancy replacing it or fiddling with it much. Also, I intend moving fairly soon, so didn’t fancy changing dishes and running loads of cables.

I’d got myself a satellite TV card for my PC, as there’s more I can do with it. It’s a Hauppauge HD-capable card, plus it sits alongside my DVB-T card quite nicely.

However, the issue still remained that I needed a satellite signal for it. I’d previously seen some small portable kits in Lidl which included a dish, LNB, and some free-standing brackets. That was a while ago, but I knew they were available elsewhere. I had a dig around on eBay and found one for £40. It’s a ‘Konig’ branded dish, with a small single-output LNB, a foot stand, a sucker-cup to stick it to a table top (which doesn’t actually work) and a wall mounting bracket.

I tried it indoors behind glass but there was just no signal at all. Apparently around 2005 glass manufacturers started using various new coatings to reflect sunlight – said coatings also reflect satellite signals. Our windows were replaced in 2008, so I really was heading down a dead-end road.

I tried the dish out in the garden, and it had a perfectly useable signal on Hotbird and Astra 19.2E. Even with the mile of cable I used it was working fine. It seemed my only real solution was to hang the dish out the window. I’ve got a good line of sight to a fair bit of the Southern horizon, so it’s a perfect position. I needed to somehow hang the dish out of the window, but in a way that was adjustable. I needed to be able to adjust the angle on the dish to catch different satellites.

After a bit of pondering, this was the result:

It’s a pretty simple right angle, strengthened to stop it wobbling. Inside it’s fitted to a double-height section, which just hangs against the window frame. The dish isn’t heavy, so it shouldn’t be a big issue. The cable itself acts as a useful safety in case the whole thing decides to launch itself to the ground!

At the moment, it’s picking up Astra 19.2E very happily. There’s a couple of things I want to address. Firstly I need to pick up a longer bolt, so I can use washers on both sides. I might try and strengthen the top arm somehow as I can see the hole around the bolt being a weak spot. Also… I can’t close the window!

But hey, I’m not complaining!

I ran various tests and found that faxes between ATAs internally were perfectly fine. As soon as they went through the gateways, they failed miserably. I ran through some of Cisco’s help guides but was drawing complete blanks. I’d ran the prserv tool to see what the ATAs were up to whilst making calls. I’d see ‘resync’ go whizzing by with a load of other seemingly random numbers. The word ‘resync’ suggested to me that the ATA was hiccuping on something, and doing something to the audio stream.

Analogue modems expect a constant stream of data. It might get fuzzy, or drop out, but it will always come along in a specific order, at a certain time. It’s predictable. Resyncing something mid-stream isn’t a good idea to a modem. In all cases when I saw the word ‘resync’ the fax would end up corrupted or dropped entirely, depending on when it happened during the call.

I did a little digging on the Cisco TAC case collection, and found what I was looking for. It was something I fiddled with some time ago.

ISDN circuits rely on a clock. Generally speaking, the clock is the telco end. We have four ISDN links on our gateways – two out to the PSTN, and two QSIG links to the old PBX. We had some odd issues with echo, and one thing we tried was forcing clock sync on the E1 controllers.

E1 and T1 controllers can exhibit something known as ‘slipped seconds’. This is basically where the clocks at both ends get slightly out of sync with eachother. In some instances it can cause echo, so we’d nailed up the QSIG links to use the clock at the legacy PBX end. However, it seems with the 2-port WICs, this causes BOTH ports to sync to that clock.

Up to this point it hadn’t been the issue. There was the odd dropped fax, but nothing overly bad. A week or so ago (the week I was off, natch), the faxes all pretty much failed simultaneously. Voice calls remained perfectly fine, which made it all the more perplexing. Luckily I found the info I needed in the TAC collection.

The issue will manifest itself as slipped seconds. On the router, I did the following:

router#sh controller e1 0/0/0
E1 0/0/0 is up.
  Applique type is Channelized E1 - balanced
  No alarms detected.
  alarm-trigger is not set
  Version info Firmware: 20060707, FPGA: 13, spm_count = 0
  Framing is CRC4, Line Code is HDB3, Clock Source is Line.
  CRC Threshold is 320. Reported from firmware  is 320.
  Data in current interval (618 seconds elapsed):
     0 Line Code Violations, 0 Path Code Violations
     181 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
     181 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
  Data in Interval 1:
     0 Line Code Violations, 0 Path Code Violations
     262 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
     262 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

There we see some ‘slip secs’.

The ‘fix’ is quite simple. I switched to the interface, and then issued the commands:

network-clock-participate wic 0
network-clock-select 1 E1 0/0/0

The first line selects the WIC you wish to use, then the second selects the clock source (interface) you wish to use. Once I’d done that, the faxes magically all worked again.

http://www.cisco.com/cisco/web/support/index.html – TAC case collection requires a CCO login.

AWESOME!

Possibly one of the coolest instruments in a long time!

In my case, I often do ISDN Q.931 debugs to find out what’s going on on my voice gateways. I’ve gotten used to it now, but typing ‘undebug all’ whilst a ton of information whizzes by is less fun than it sounds.

Today, I found this useful command:

“logging synchronous”

If you enable that on your vtys or con (or aux) ports, it basically causes IOS to dump the debug still, but it’ll do it on all other lines EXCEPT the one you’re typing on, leaving it alone. I imagine it could cause some slowdowns as it has to draw your command in the same place, whilst interleaving other junk, so it could potentially cause problems on a direct console, but if you remotely telnet (I really should enable SSH one day), it’ll be a lot easier to see what’s going on.

Here’s the gist of what you need to do:

  Router(config)#line con 0
  Router(config-line)#logging synchronous
  Router(config-line)#line vty 0 4
  Router(config-line)#logging synchronous

Then wr mem as usual.

Easy!