Every tech geek has his/her preferred tools and one of mine is without doubt Tobi Oetiker’s MRTG (Multi Router Traffic Grapher), which I’ve used to make pretty trend lines of much more than routers or traffic.
MRTG is a Perl program that grabs some measurement values (typically via SNMP) and plots them as time series. It creates ‘daily’, ‘weekly’, ‘monthly’ and ‘yearly’ graphs and the HTML page that shows the graphs and some min/max/average statistics to accompany the graphs. You’ve probably seen the typical MRTG output images before:
But MRTG can do more than just SNMP. In fact MRTG can plot any trend, as long as it gets its input in the form of 4 text lines:
The I value becomes the green bar graph, the O value becomes the blue line, and the rest is only used to generate the following line in the generated HTML pages:
The statistics were last updated Tuesday, 13 October 2015 at 10:40, at which time ‘[server name]’ had been up for [uptime].
Continue reading Idea: Extended MRTG format
Some drivers love fancy chrome wheel rims, some add a huge wing spoiler on their car, or fuzzy dice hanging from their rear-view mirror. Me, when I bought my new car, I decided that I wanted a Wifi network in my car. So that any passenger with a laptop/iPod could read his email. And I imagined driving to distant holiday locations while my passenger where watching movies streamed from a NAS disk built into the car.
This weekend I finished episode one: Internet in the car. I used the following components:
The important details here are:
- The Huawei stick is compatible with the TP-Link router.
- The Huawei stick can be configured with ‘Save my PIN’, so that when it starts up, it connects to the 3G network without any manual intervention.
- The TP-Link router runs on 12V DC (which is what a car has)
For the rest, the exercise was quite straight-forward: I configured the Huawei stick on my laptop with the right PIN code, popped it in myTP-Link router, configured the right 3G settings for Telenet (see here). Then I took an old 12V power transformer, chopped off the connector and linked it up to an old car cigarette lighter type of plug (sometimes it’s good to have an archive of obsolete cables and power supplies). I then hid the router under the base plate of my trunk, where there is also the battery (the BMW X1 stores the battery in the back, where you would normally have the spare tyre). I switch on the car and 20 seconds later, I have a Wifi network “OnTheRoadAgain” that is connected to the Internet. Proof of concept is OK!
The next step now is to add a (Synology) NAS, which also runs on 12V, and hook up my iPad to the car Wifi to view my collection of backed-up DVDs from that disk. And maybe run some extra programs (e.g. MRTG for monitoring) on that NAS. To be continued!
My mobile provider Telenet had a partial outage today. Sometimes calls would go though, sometimes not. Same things with SMS and 3G. I wanted to check if there was a page I could check to see if it was just for me, just for that location on globally in Belgium. You know, a proper status page like Google and Apple have. Or in Belgium, like Combell. It appears Telenet has one, but it’s for the Internet division. They also have a Twitter account that is well followed up. How does this compare to the other providers? Here is an overview of who offers what:
Telenet (on Mobistar network)
Base (part of KPN)
Mobile Vikings (on Base network)
Scarlet (part of Belgacom)
Kudos to http://www.ionasj.com/welk-netwerk-voorziet-de-beste-dekking/
Something has been bothering me for a while. I have a colleague that needs to post some files on a site every week, and she needs to do it via FTP. FTP is ‘geeky’ for most people. Their PC does not come with an FTP program installed, they never need it for daily web usage and they’re not sure how it is different from email/web upload. I ended up installing Filezilla for her and she manages, but it would be so much easier if I could tell her: just email it to XYZ@example.com and it will arrive on that FTP server. Sending email, everyone can do.
Another issue I had is that I would like to offer a service (that involves audio manipulation of WAV files) and I would like people to send an email with the file attached and I send back the result. In both cases, the problem is the same: email now arrives in a mailbox and is expected to be handled manually. I would like a platform service: I pay for the usage of an email address, and every mail that arrives there triggers a number of actions that are automatic.
Not just a service, a platform
Of course I’m not the first one to think of this. Flickr allows for posting pictures via email (I use that a lot), you can send your blog posts via email with Tumblr, Posterous and even WordPress. Customer support services allow auto-responding on incoming emails with suggestions for resolutions. It’s just that all these services are specific to the provider. To do it, you have either poll for incoming email (check your POP3 box every N minutes) or build/configure an SMTP server that handles incoming email. If you’ve ever encountered the black magic involved in configuring a sendmail/postfix/qmail server, you know that’s not for everyone. Me as a web developer/hacker, I want to configure: mails sent to XYZ@example.com are posted to my web page with the email body, sender, attachments (as URL), or published via a private RSS feed, and that’s how I get them into my workflow.
The funny thing is that a much more limited communication method, SMS/texting, has these platforms. There’s Twilio, Fortumo, Tropo, that allow you to receive text messages and make them trigger things. The US providers even allow for setting up automated IVR (Interactive Voice Response – a.k.a. “Press 1 for …”) application through these services.
So, the idea
So what could this platform look like?
- I register for the service and I get the prefix ACME
- I then start defining my services: email@example.com, firstname.lastname@example.org, email@example.com
- I configure acme.upload to save attachments to an FTP server and send a confirmation email.
- I configure acme.support to send a confirmation email with a unique number and forward the email with this unique number in the subject. Also, I get an SMS.
- I configure acme.register to take .XLS files, convert them to TEXT and post them to a web service I have created. I also get the sent emails in an RSS feed.
- I now create my ‘public’ addresses: firstname.lastname@example.org / email@example.com / firstname.lastname@example.org and forward these to the email addresses I created above.
- I get daily/weekly reporting, spam detection, and unlimited scaling.
Do anything like this exist?
I remember that before I started photography on a serious level, I had some understanding of shutter speed, but none of aperture and focal length. Even when I read what they meant, I still couldn’t ‘picture’ it, had no feeling for the numbers. Let’s leave ‘aperture’ for another time and just concentrate for now on the concept of “focal length”
First of all, the focal length of a lens is not the same as the actual physical length of the lens. Yes, 200mm and 300mm lenses (telephoto lenses) tend to be longer, but they’re not exactly 200mm and 300mm long. For instance, the Sigma 55-200mm F4-5.6 DC HSM is 85mm (3.3″) long, while the 70-200mm F2.8 II EX DG lens is 184mm (7.2″). Same maximal focal length, but more than twice as long.
So what is focal length? I could explain that it is “the distance from the center of the lens to the principal foci (or focal points) of the lens“, but that wouldn’t make it more comprehensible, would it? Well, I read through the theory, with tangens of the viewing angle and stuff, and I think I understand it (I’m an engineer, I actually like trigoniometry). A 200mm lens gives a viewing angle of 12° on the diagonal. Still not clear? That’s when I thought: let’s invent something more tangible: the “portrait distance“. Say you need a surface of about 72cm x 48cm (28″ x 18″) to make a portrait of a person (not just a headshot, but with some torso on it too). See some examples below:
Well, the distance between the camera and the person you’re making the portrait of, will be +- 20 times the focal length.
Continue reading Focal length for the common man: “portrait distance”
I was downloading a free iPhone app at noon, and I thought: some of these applications have no good alternative in the browser world. Imagine everyone could start using/buying the Apple iPhone/iPod Touch applications right in their browser. You give your Apple ID, you purchase an app like ColorSplash and off you go. Some of the multi-touch interface would be hard to emulate, but still. It would have to be an Apple application that does it: like e.g. iTunes. It’s got your Apple ID anyway. Why not run a virtual iPod Touch in there?
- some applications for iPhone/iPod just have no worthy counterpart in the ‘normal’ world.
- an application would run immediately on Apple MacOSX as well as Windows XP/Vista/7
- the iPhone developers wouldn’t be looking anymore at a potential audience of some X million iPhone owners, but at all iTunes owners.
Research analyst Sam Bhavnani, of the market research firm Current Analysis, says that iTunes has 200 million users. Research analyst Shaw Wu, of the market research firm American Technology Research, gives a figure of 100 million. Oddly, Apple itself gives a much lower number: 10 million.
Seth Godin came up with a visualisation of ‘means of communication’: bandwidth vs sync(chronicity). He took a number of ‘old’ (postal mail, radio) and ‘new’ (blogs, Youtube and -of course- Twitter) technologies and ranked them on a 2D graph according to ‘quality’ (density or bandwidth) and ‘sync’ (speed of reaction).
Although it is an interesting way of visualizing things, and I consider Seth a very bright and creative guy, I am bothered by the fact that the graph is neither clear, correct nor complete.
Continue reading Seth’s bandwidth vs synchronicity graph: it’s a start
Ok, she’s not Kate Moss, and he’s not Inspector Morse, but you get the general idea. If you father a child once you’re past 70 years old, the kid’s gonna have bags under the eyes.
made with www.faceresearch.org/demos/baby – via infosthetics.com
On a totally unrelated note: thanks for all the nice emails, SMSes, IM’s and other Facebook pokes I received for my 38th birthday. If I didn’t reply immediately: I had a wonderful weekend with the woman I love. I can only hope the rest of the year will continue on the same elan.
Look wat ‘experts’ are still telling in the courtroom:
The HP Pavilion computer obtained from McGuire’s attorney’s office had a 60 gigabyte hard drive, and not all of it was searched by Seymour.
She told the jury that it is known in the computer industry that if information stored on a 12 gigabyte computer was put on paper it would create a stack of paper higher than the Empire State Building.
There was a time once when PCs were just overevolved typewriters and it made sense to express everything in “number of pages”. That time has long gone. Let’s convert that 12 GB into today’s storage currencies:
- 12 GB is the equivalent of 17 CD-ROMs of data (700MB)
- not yet 3 full DVDs (4.7GB)
- Not even one HD-DVD (15/30GB) or Blu-Ray (25/50GB) disc
- 4000 3MB (+-8 megapixel) pictures in JPG format
- 12 days of MP3 recordings (at 96Kbps)
- 16 episodes (not even one full season) of Lost, Prison Break or Heroes
Moreover, a conversion to typed-out A4s only makes sense if you specify font-size, spacing, margins and usage of duplex printing, in which case it remains an impractical antiquated unit.
A jury full of technophobes/non-experts shouldn’t be baffled with exaggerations like a “tower the size of the Empire State”. If you do not take into account the operating system, programs, images, music and movies, what remains on a hard disk of searchable data created by the owner? Maybe 2-5 gigabytes, thanks to MS Office’s bloated file formats. And the most important stuff for computer forensics is maybe 5MB: browser history, cookies, IM transcripts, emails and Office documents converted to text.
After a conversation with Ine on HD formats (1080i vs. 1080p), I researched the topic a bit further. Let me resume some of the things I have learned up till now:
Real HD and HD-ready
HD or ‘high definition’ as defined for screens, projectors and TV, defines 2 resolutions. The smaller one has 720 lines of each 1280 pixels, the bigger one 1080 lines of each 1920 pixels. They can be used with different frame rates: refreshed at 24 fps (a common movie standard) up to 50/60fps (often used for TV). To limit the necessary bandwidth in some cases ‘interlaced scanning’ is used: 1 frame contains all the odd lines, the next only the even lines. This effectively halves the throughput, at the cost of image quality (rapid moving lines appear jagged).
The two most common formats are:
- 720p60: 1280×720, 60 fps progressive scanning, used e.g. in USA-based HDTV broadcasts
- 1080i50 or 1080i60: 1920×1080, 50 or 60 fps interlaced scanning. The higher resolution makes it better for larger screens and movies, but the interlacing has a bad influence on fast moving images (like e.g. sports).
What kind of resolution do we have now? Regular digital TV (SD or ‘Standard Definition’) consists of 480 lines of 720 pixels each. DVD, for instance, allows for 480i and 480p. So, HD delivers at least 3x that resolution.
“HD Ready“, a label that a lot of TVs/screens carry now, just indicates that:
- The minimum native resolution of the display (e.g. LCD, PDP) or display engine (e.g. DLP) is 720 physical lines in wide aspect ratio.
- The display device accepts HD input via Analogue YPbPr1, DVI or HDMI
- HD capable inputs accept the following HD video formats: 1280×720 @ 50 and 60Hz progressive (“720p”), and 1920×1080 @ 50 and 60Hz interlaced (“1080i”)
- The DVI or HDMI input supports content protection (HDCP)
from eicta.org (PDF)
Even if the display can only show 720p, and so must ‘downsample’ an incoming 1080i signal to that lower resolution, it can be called “HD Ready”.
Continue reading HD – 720p, 1080i and 1080p