At sea!

We’re sailing again!

sea

It’s so lovely being back at sea, and David seems to quite like it too.  He actually slept right the way through the night the first night!  Amazing… (If only he’d do it again…)

AV work is going reasonably well.  We’re doiteamng loads of training, as much as possible, but still trying to get everything working again too.  It’s really hard trying to arrange work for people to do, who know nothing about A/V at all, and may not have even touched a sound, lighting, or video console before joining the team.  Still, they’re all great people, and we’re having a lot of fun.

 

fanroomOne very frustrating thing was that I had to fix the Deck 4 music and paging system.  For whatever historical reason, that’s part of A/V’s responsibility, rather than the electricians.  The rack is located in a loud noisy fanroom, full of dust and grime.

 

wiresThe rack isn’t very accessible, and getting in to the wires is really really awkward and scrapey.

 

It’s not massively well documented (another task on my list…), and I think several people had tried to fix it recently, so all the settings were messed up.  In the end, I pulled out the entire system, took it down to our storeroom to clean and test and set up, and then brought it back and plugged it in.  It all worked!  Which was great.  It just then took ages of walking around with the team getting them to tell me which zones were connected and had the right volumes, and so on.  Not fun, and as it needs to be working before we arrive in the next port, it meant I had to do that for 4 days rather than work on any of our venues. Grrr…

The new portable ‘fender’ sound systems that we bought are a huge success.  They work really well.  I asked one of the new A/V team to paint ‘Logos Hope A/V’ on the side of them all so that they don’t get lost, or apprehended into some other department.  I was expecting something ugly but functional.  Instead I got this:

logo

Really cool!

Anyway, to end this post, here’s a photo of David from when we took him to the kids water zone at the mall in Singapore.  Wet as a fish, a nappy as wet as he, and as Becky puts it, “Happy as Larry”. (Whoever Larry is…)

happy_as_larry

LVM snapshots for a resetable machine

I have ended up maintaining a few websites which we are hosting on a machine off in Germany somewhere.

I want to get everything automated, so I have less work to do if something goes wrong.

I’m using ansible, which is wonderful, and have a nice set of playbooks I’ve written which take a raw CentOS install, and install everything, (php-fpm, nginx, etc…) set up the virtualhosts, install wordpress & joomla and all that for the sites that need it, etc.

Until today, I’ve been using a virtualbox on my local computer to test on, and it works great.  I haven’t bothered with vagrant, as I tried it for a couple of days, and it crashed my whole computer twice, so I gave up.  With virtualbox, it’s almost as simple.  I have a virtualmachine which I can spin up, install stuff on, and then when I want to go back to a fresh machine, it’s a matter of turning it off, and clicking ‘restore snapshot’ to the snapshot I made when it was clean installed.

It’s practically instant, and just works.

However, running a virtualmachine on my primary work computer all the time does make everything else somewhat sluggish.  So I’ve scrouged an old computer that wasn’t doing anything, and am now using that instead.

In order to get snapshots and restore points going well, here’s how I did it:

  1. Install CentOS, leaving a bunch of free space on the LVM primary group.
  2. Make a snapshot when it’s first installed
  3. Restore (merge to) that snapshot whenever I want it back to original settings.
  4. Reboot

To make & restore the snapshots, I’ve written the commands as scripts so I don’t have to remember the lg-whatever stuff. (vg_localtest is the name of the volume group I set up for the HD when I installed):

/usr/sbin/snapshot_make:

#!/bin/sh
lvcreate –size 100G -s -n original_snapshot /dev/vg_localtest/root

/usr/sbin/snapshot_restore

#/bin/sh
lvconvert –merge /dev/vg_localtest/original_snapshot && reboot

It works great so far.  One improvement I’m making, since I one time forgot to make a snapshot, and so couldn’t restore to a blank slate without re-installing the whole thing (which, admittedly, only takes half an hour or so):

I’m adding ‘snapshot_make’ into a boot script, and then modifying it to remove itself from the bootscript once it’s made the snapshot.  That way as soon as the machine reboots into it’s original snapshot, it will automatically re-create the snapshot.

This looks like:

/usr/sbin/snapshot_make:

#!/bin/sh
lvcreate –size 100G -s -n original_snapshot /dev/vg_localtest/root

sed -ine ‘/snapshot/d’ /etc/rc.local

and then /etc/rc.local will look like:

#… whatever it has
/usr/sbin/snapshot_make

Merging directories with the magic of Python.

We finally got the last projects out of that monstrosity ‘Final Cut Server’, but one project at the end was a nightmare to export, and we weren’t sure which files from the end actually were in a different version of the project that we already had.

We essentially needed to merge two different versions of projects directories, making sure not to lose any files, and we didn’t want to lose the organization of the files.

Here’s a quick python script I wipped up to make it quicker.

With the 4000 odd files in the project, it took under a second to run, and it turned out we only had about 20 files which hadn’t already been merged.  Much simpler to sort out.

The script took about 10 minutes to write and test. This is why you should learn to program.  Hacking stuff like this up is easy, and saves *so* much time.

(Yes, you probably could do this with a couple of lines of perl or BASH, but what the heck.)

#!/usr/bin/env python

from subprocess import Popen, PIPE
from os import stat
from os.path import basename, abspath

def run(*command):
    found = Popen(command, stdout=PIPE)
    return found.communicate()[0]

def files_in(dirname):
    return [x for x in run('find', abspath(dirname), '-type','f', '-print0').split(chr(0)) if x]

if __name__ == '__main__':
    from sys import argv

    try:
        sourcedir = files_in(argv[1])
        destdir = files_in(argv[2])
    except IndexError:
        print 'Usage:'
        print argv[0], '  '
        print 'Where you want to check if files in  are also in '
        print '(but perhaps with a different relative path)'
        exit(1)

    print '---------------------------------------------------'
    print '{0} files in {1}'.format(len(sourcedir), abspath(argv[1]))
    print '{0} files in {1}'.format(len(destdir), abspath(argv[2]))
    print '---------------------------------------------------'

    destnames = {}

    for destfile in destdir:
        destnames[basename(destfile)] = {'size': stat(destfile).st_size,
                                         'path': destfile }

    for newfile in sourcedir:
        base = basename(newfile)
        if base not in destnames:
            print newfile, 'is NOT in the new dir'
        else:
            destfile = destnames[base]
            if stat(newfile).st_size != destfile['size']:
                print '{0}({1}) differs from {2}({3})'.format(
                      newfile, stat(newfile).st_size,
                      destfile['path'], destfile['size'])

Ergonomic things.

I get wrist pain in … well, obviously, my wrists.

Man, that was a bit of a daft start to a post.

Especially when using a mouse, but also when I have to do a lot of typing.  I do touch type, but not ‘formally’, with perfect  full-hand position, and so on.

Anyway, to try and make things better, here are some of the things I’m using

Microsoft Natural 4000 Keyboard

One of the weird things about keyboards is that essentially, we still use the exact same design that was needed for swinging arm typewriters. Stuffing all the keys as close together as we can, in orderly rows, so that the arm can hit the paper in the same place every time.
Actually, though, our hands would be a lot happier somewhat spaced apart, and at an angle, rather than trying to line up next to each other.

I have been using one of these Microsoft Keyboards for over a year now at work, and although it’s not perfect, it is a lot nicer than regular cheap and nasty keyboards, and a lot cheaper than some other Ergonomic Keyboards.

I currently have it at home, as, since this is a bit of a quiet time at OMNIvision, I thought I should finally get around to learning a more sane keyboard layout than QWERTY.  I’m learning Workman, which is a little obscure at the moment, but to me makes sense.  We’ll see if it takes off at all in the future…

Kensington Trackball

  
 The thing which makes my wrists hurt the most is using a mouse, so I’ve been playing for a while with using the popular alternative to mice: trackballs.  This one is really cool, in that it has a built in scroll wheel.  That’s normal on mice, but for no apparent reason, is kind of unusual on trackballs.

I’m not 100% sold on trackballs as the answer, I think probably as big a part of it as anything is having to reach way over to the side and grip at an angle.  So I try to keep the trackball in the middle of the desk, and I have it also on an angle using an old empty CD spool.

Wowpen Joy

At home, I tried for a while using another trackball I got on ebay, as it was cheap, as it was second-hand.  It also wasn’t very reliable, so it ended up being more frustrating than helpful.  I then looked at Vertical Mice – mice which are designed to keep your hand in the ‘handshake position’ more naturally than the twisted flat position of normal mice.
A lot of vertical mice, like ergonomic keyboards, are pretty expensive.  However, on ebay there were a lot of these incredibly named ‘WowPen Joy’ mice.  The name itself is enough to put you off.  Anyway, I thought I’d try and see how one was.  It’s actually very nice.  It is kind of small, but still works fine with my big hands, I just use my middle and ring fingers to click, not index and middle.
Yes, I think it’s helping.  But still sometimes my wrists are painful, so much that I have to stop mousing or typing at all for a while.  I need to work on my posture, I think.  I’m considering trying a standing desk at work for a few months, as whenever I sit I do tend to slouch, no matter how many times I try to remember to sit up properly.
I also use “Time Out” computer break software on my work machine, which is really annoying, but almost certainly a good idea. Every so often it jumps up on my screen and tells me to stretch, and take a 10 second break from the keyboard, and then every 45 minutes or so, tells me to take a 5 minute break, which I use to do some cleaning, make coffee, go hang out with someone, or get one of the other non-computer jobs done that I need to.  Sometimes, if I have nothing else really to do, then:

Contact juggling

I keep a contact juggling ball around, and play with that during the micro breaks, which is supposed to be good for muscles and stretching…

So why, you may ask, am I writing all this boring waffle about keyboards and so on.  Well, partly, because it is kind of interesting to me. Partly it’s because I do find it easier to get started writing about factual/techy stuff – maybe that’s part of being an INFP, extroverting my TJ side, I dunno.  I have some more philosophical thoughts which I can relate through all this geeky ergonomic clobber. I’ll post it soon.

Super fast review of the past few months.

Foolishly, perhaps, we thought this year would be a quiet one.
A couple months on the ship at the start, then back in the UK until August, Teenstreet in Germany, and then back home for the rest of the year.

There’s a quote regarding the fallibility of apparently structurally sound plans of humans and rodents which might be appropriate around here.

When we finished our time on Logos Hope, we were in Bangkok.  Our organisation was holding a conference there at that time, so we helped out with the A/V techie arrangements for that.  When that was over, Becky headed home to Carlisle, and I went North for a week or so as cameraman, filming and visiting with one of our teams in the region.

After I got back two weeks later to the UK, We had a couple of weeks ‘normal work’, before I had to go to Ireland to run sound for an Event in Cork, as one of our other Sound Engineers needed to go back to Korea for surgery.

After getting back to Carlisle, we had about two weeks before we’d scheduled a couple of weeks in Cyprus, to take the Christmas break we’d missed on the ship, and take some time off, in lieu.

Two days before we were due to leave Cyprus, my Grandmother in Birmingham passed away, quite suddenly – although not totally unexpectedly – and so we returned to the UK with my parents and brother for her funeral.

We were then in back to Carlisle for a few weeks, before travelling over to Germany for Teenstreet.

While we were at Teenstreet, the arrangments came together for a filming project my Dad has been planning for a while in Cyprus, so instead of coming back to the UK, we headed over to Cyprus again to help with that, myself doing the sound recording and Becky the shoot documenting and general assisting.

We’ve since been back in the UK for just about three weeks, and so wondering what’s going to happen next.

Right now we have our friend Ant, staying with us, and he inspired me to start blogging again.  This may not be the most exciting post in the world, but it at least starts to cover the great gap of the last several months.

You should check Ant’s Thoughts About Job.

Documentation, and how balanced audio cables work.

I finally had a bit more time this morning to write a bit more in the A/V manual.  There’s lots of bits and pieces of documentation on board, but no comprehensive single getting started manual.  So I’m writing one, bring together bits and pieces from all over the place, sorting out what documentation there is, updating schematics, etc.

Anyway, here’s the rough version on the article I just wrote about how balanced sound cables work.  It’s pretty much my standard explanation of Balanced Audio, and aimed at people coming to A/V from a non-techy musical background, rather than for Electronics Engineers.
You may find it interesting.  Then again, you may not.

—–


Sound is basically vibrations in the air.
TODO: more details, pingpong ball analogy? 

Inside an (SM57) Microphone head.
That is the bit of plastic and the coils!

This translates really easily into an analogue electrical signal: you simply turn the air vibrations into voltage vibrations.  A Dynamic microphone does this by having a small bit of paper (or plastic) which vibrates with the air around it, and pushes against a very small copper coil which, moving inside a magnetic coil itself, generates a very-very-very small amount of electrical current.

 TODO: more pictures.
This gets dumped down a wire, which gets amplified by (you guessed it) an amplifier into a very big amount of electrical current, which then drives a big electromagnet inside a speaker, which pushes another copper coil around, which is attached to another big bit of paper (the speaker cone), which causes the air around the speaker to vibrate – with the same vibrations that the microphone vibrated with, just bigger.
Simple, isn’t it? (well. Kind of.)

Balanced Audio Cabling

The trouble with simply dumping an audio signal down a cable, and picking it up at the other end is that your signal line, and return (usually ground) will pick up noise (say from A/C mains electricity, fluorescent lights, dimmers, mobile phones, etc)  along the way.

Here’s an original signal:


And here’s some noise:

 

 And the result:

This is a Bad Thing™.
So some clever engineers, back in the deep recesses of time figured out the following:  You could take a signal, and before sending down the wire where it could pick up noise, invert it:

If we add the signal to the inverse, you get a grand result of nothing (e.g. -3 + 3 = 0).
Now, if we throw these two signals down a pair of very similar cables twisted round and round each other like crazy, then they’ll both pick up noise pretty much the same as each other:


Note that 3 (the original) + 1 noise = 4,
while -3 (the inverse) + 1 noise = -2. NOT -4!
This is really cool, because if we add these two signals together, we don’t get 0 anymore, we get no original signal, but you do get the noise (doubled).

 

So we’ll use our amazing maths skills again, and divide this doubled noise in half. (2/2 = 1).

And we can subtract this 1 noise from the noisy original signal (4-1=3)

Voila! The original clean signal is back again.

  This is (roughly speaking) how balanced audio works.  And since almost all professional audio equipment runs with balanced circuitry, all we need to do is make sure the cables are in good shape, and then everything works magically with hardly any noise.

This is why for balanced cables (XLR/Mic, or TRS jack) you have 3 pins: +, -, and ground.  The ground is connected to a wire-mesh sheath around the other two, to try and keep as much noise away as possible.
(Technically, you don’t need to invert the signal, you could just use an empty zero, but for various impedance, op-amp, techy reasons, it works better if you do.)
Sometimes the ground wire will pick up noise itself, or due to being connected to different grounds at both ends of the circuit (say a piano on stage, and the A/V room sound desk) it will end up with a bit of random leaked current running down itself.  This can show up as noise, so you often use a Ground-Lift switch to disconnect the ground at one end or the other, which can sometimes help.
A DI box takes an unbalanced signal, and turns it into a balanced one, which means you can send a signal a long way without noise.
Remember how the two wires have to be twisted together like crazy?  This is so that if there is some noisy thing (like a flurescent light) nearby, both wires will be equally effected.  This is so important, that for broadcast audio, sometimes cables with 4 or more wires are used.  The + signal on 1 & 3, the – signal on 2 and 4, and then all of these are twisted together.  There are brand names of these cables such as QuadStar, etc.  Usually this is somewhat overkill for regular live sound though, as the cabling is much stiffer and harder to use day to day.

——–
So, what do you think?

at quinta again

Back from Spain. It went really well. Really great people, and it was cool helping to support technically all these guys who are so excited by what they’re doing.

Quite a surprise that some friends from Cyprus were particpants at the conference! So it was quite cool meeting up with them!

We’ve been back a week now. Becky was with some friends down south, and I was up in Carlisle finishing off some projects, and then we met up again on Friday, here at the Quinta.

Last time I was here, was for a few days break after my first 2 years on Doulos. I’m now here with Becky for a couple of days debrief with our home-office, and talking to some of the new people who are joining the company in september about life on board the ships.

It’s again quiet, relaxing, and also very good hanging out with some of my friends from the Doulos who are living and working here now.

I managed to spend catch lunch with my brother and some friends in Birmingham on the way down.

Here’s a crazy story:

Trying to buy tickets to get here, straight from Carlisle to Quinta would cost 40 pounds+… but if I booked Carlisle to Birmingham, and then Birmingham to Quinta, it cost 26.

I do NOT understand why. I blaim computers. They’re evil. It’s all a conspiracy.

We only have a few weeks more at Carlisle, for now, and hope to fly to Cyprus in about a month. Probably.

Then, hopefully, God willing, etc, to come back here for a few years starting some time in the summer.

We’ll see how that all goes.

So… Blogging.

Today marks 2 months of Becky and me being at OMNIvision, up in Carlisle. Time… is weird. It has gone so fast, and yet it seems like we’ve been here for only a few weeks, and yet Doulos is like another world away in the past.

I guess there will be another 200 odd people around the globe feeling the same way right now… and about 300 people every year have been feeling that for the last 30 years.

Our work is a bit random – we hardly know what we’ll be doing, one day to the next. We spent a lot of time in our first week or two pulling wires out of a big OB truck, then about 10 days sorting out books, inventorying, etc, then a few days moving a server rack across the building, including making and crimping all the new cables/extensions. Then a bunch of random small editing projects, a live concert in Manchester (me on a camera, Becky as my “cable monkey”), Becky is working a lot on admin stuff – figuring out some of the shipping arrangements for equipment, and writing the OMNIvision manual, and I’ve been doing some cleaning, sorting, lighting design, editing, fixing stuff, inventorying equipment, measuring cables, pulling electric cables through ceiling spaces, writing 30 second advert clips, and so on…

Yes. Quite busy.

And yet, not… it feels in some ways a lot more relaxed and slow than Doulos… yet also it feels a bit like I have less free time.

Becky and I live about 20 minutes walk apart, and neither of us have cars. The Office – where we go 2 mornings a week – is 15 minutes one direction, and the Studio – where we work the rest of the time – is 20 minutes the other direction. Busses are slow, somewhat irregular, and expensive, so we’re spending a LOT of time travelling. Also all the regular domestic stuff – cleaning, cooking, washing up, etc, takes time. On Doulos, I’d frequently be working until 6.15, pop down to the dining room, grab a plate of food, and the continue working while eating my meal. Same for lunch, and often Breakfast. Here, a meal can take over an hour. I guess it’s good, helping me to slow down… but BOY is it frustrating.

Like yesterday, I hoped to get a video project edited and finished… but then after Prayer Breakfast at the Office, I got a lift to the Shed (where we keep the vechicals), and picked up some equipment there, then got a lift to the Studio, and it was already 12.30. At lunch, there were a whole bunch of announcements and talking… and then with computers taking a long time to work, and Final Cut Server being a pain, I didn’t actually get to editing until 2.30pm!! And then Final Cut Pro decided to act stupid and to forget half the work I did with the Multi-Camera Editing tool (which otherwise is VERY cool…)…. So I only really got about 2 hours work done. Still, I’d done enough prep work with the lighting to make the keying and stuff a fairly easy job. I spent most of today editing too, and so that’s another piece basically finished.

I’m not sure if I like editing and that or not… in some ways it’s a lot of fun, and I do enjoy it. Yet I also miss “live” theatre.

So. That’s a bit about what we’ve been up to. I’ll blog more about future plans… in the future.

AV updates, mid drydock.

Before:
After:

I think it looks a little better. Still messy, but at least understandable. Pretty much everything is plugged in now, and from preliminary tests, we appear to have somewhat better clarity in EVERYTHING, and some of the video signals are visibly higher signal-to-noise with much less interference.
We bought two new audio patch panels too, Behringer ones. Strangely, Behringer also seem to do unbalanced patch panels. Fortunately, the shop had both, and I noticed. What on earth would anyone want unbalanced patch panels for?!

I also had to butcher the two panels which we were replacing to get enough parts to fix a third panel which was very glitchy. Here are some of the internals which are slightly broken.

You can see a bit of corrosion on the top contact – even with jackplug cleaners and everything, the equipment is just plain old.

Today, hopefully, I can do the full system tests (need to borrow a oscilliscope and reference signal generators…), and then get the whole thing boxed up and leave it until the end of drydock. Then I can work on more fun projects. Videos, song composition, etc.

That’s all for now, I’ll post more shorter posts later, with more pictures.