The Python Cheese Shop is quite cool, and I'm slightly suprised I didn't know about it much earlier. I guess that is the disadvantage of getting myself of the mailist list. It provides a large range of python modules for random thing, basically Python's CPAN equivalent. It's better than google for finding python modules. In particular I managed to find something that reckons it can edit JPEG EXIF data. (Of course the other two libraries I found don't appear, so I guess google isn't totally useless ;)

Anyway, I'm starting to upload my modules, in particular pyannodex and pexif.

I've just released 0.7.2 of pyannodex.

This version fixes some bad sgfault bugs, exports some more of the annodex functionality, and adds a python version of the anxinfo tool.

I've bumped the version to 0.7.2 from 0.1 to push it in line with the libannodex version numbers.

So not everyone can be a brilliant speaker like Damian Conway, but you can at least apply yourself to the standard of not sucking.

Here are some ideas not on how to be a good speaker, but just how not to suck.

Turn off your screensaver.

Do you have any idea how annoying it is when the overhead flickers on and off every minute?! It is a really brilliant way to distract your audience. And it will also distract you as you have to wake up your laptop every minute.

Use a large font size.

If you are presenting a subject to nerds, then chances are a large portion of them have sucky eyesight, so just bump the font size up a couple of points, please. On the plus, this means you will have less crap on each slide, therefore making your slides better anyway.

Look at the audience, not the overhead screen

Eye contact is nice, back contact less so. Don't look around at the screen to work out what you are talking about. Most laptops let you have it show what is on the screen, so if you must cheat, look at the laptop screen, not the overhead screen.

Don't mumble to yourself

If you realise some problem or something during your presentation, don't mumble about it to yourself. Just move on -- the audience probably won't notice it anway.

Stick to your allotted time

If you are given a 20 minute speaking slot, speak for no more than 20 minutes. Otherwise you run the risk of the next speaker hating you for taking up their time, or the audience hating you because they want to get morning tea. (Note: You may be able to get away with this if you are a really good speaker, and enthrall the audience, but not if you are just an ordinary speaker.)

P.S: I'm not saying I'm a good speaker, I'm ordinary at best, but I do try best not to suck.

of source code is what Gernot Heiser, John Ferlito, Conrad Parker, Jamie Wilkinson, myself, and a host of around 20 other other, mostly ex-UNSW students just paid for a copy of the revered Lions' Book.

That's right, between us, we kicked in $10,000 Australian dollars to buy a copy of the book which has been signed by both Ken Thompson and Dennis Ritchie of UNIX fame, along with Kirk McKusick who wrote the Design and implementation of the 4.3BSD UNIX Operating System, Eric Allman author of sendmail, and Linus Torvalds creator of the Linux kernel. It also had the signatures of all the speakers from the 2006 linux.conf.au.

Of course with any LCA bidding process there were some other non material rewards on offer. With the $10,000 bid we also won a lot of hair, including Rusty's mustache, Jdub's hair, and Greg "Groggy" Lehey's beard! OMG! LOL!

Oh yeah... so why were people happy to offer such money and go to such lengths, on one side, it is the awesome respect people have to John Lions, who is a leading light in the idea of open source UNIX. And also I think the respect graduates have for UNSW's School of Computer Science and Engineering. The money from the auction will go towards creating a perpetual chair in John Lions' name. And even better, Linux Australia is contributing massively by matching the bid, raising the donation to $20,000 and USENIX is doubling this again to give a grand total of $40,000 towards the Opearting Systems chair at UNSW. This is pretty impressive! Hopefully by the time linux.conf.au rolls around next year, we will be able to announce that the chair is fully funded!

Oh, and a big thanks to John maddog Hall for organising the auction and the prizes.

Short version: I release some code. It edits EXIF data.

Long version: All I wanted to do was write some simple code to add a GPS location take to my photos. It should have been easy. A couple of hours of scripting at the most. But it wasn't.

Most JPEG images have some meta data at the front of them telling you stuff like, when it was taken, what camera took it, wether the flash was used, and so on, and so on. The latest version of the spec also has a bunch of fields for storing GPS information. Unfortunately my cheapo camera doesn't store that kind of information, so I want to add it in after the fact. I thought I could just grab an existing EXIF editing library and away I would go.

Unfortunately the two Python libraries out there pyexif and EXIF.py, only handle the parsing of EXIF data, not the updating of it. The also seemed to be a C library libexif that claimed to do editing, but it was basically undocumented, I couldn't work out how to use it, and besides I wanted to write in python not C. (And I didn't feel like writing a Python wrapper for a library I didn't uderstand.)

This led me to writing some of my own Python code to try and just do enough to insert the GPS tags and nothing else. Unfortunately the way EXIF works things aren't quite that easy. Inside the file format you end up with internal offset pointers, which means if you change the layout (by inserting some extra tags), you end up needing to change all these pointers to work with the new offsets.

I thought this wouldn't be too bad because I'd just append to the end of the section I was working with, (which was unfortuantely first), and then the other sections could move freely. Unfortuantely these pointers don't reference from the start of a section, they reference from the start of the file. This basically means that I need to parse everything into memory, and then know how to write it all back out again. Pain, pain, pain. (This was of course a bit of a simplication, so please don't email me saying that isn't exactly how EXIF is structured.)

Anyway, I now have a library, which can read all the EXIF data, including the thumbnail section, edit and insert values into it, and then spit out a valid file again. Now I can start writing the code to do the actual tagging, which should be more interesting than this stuff, but right now, time for the LCA dinner.

In the morning I attended the writing a gcc front-end tutorial. This was really interesting to find out about the internals of GCC, and also got into some of the new features gcc will have in the future. While being intersting, I think if I was writing a new language right now, I would still do the classic approach of outputing C (or maybe C++) and then passing that to the normal compiler.

Jimi Xenidis gave a cool talk about the new Cell processor and (failed) attempts to optimise the zeroing of pages. The basic idea of this work is to zero out pages in the background and keeping a set of zeroed pages ready, rather than zeroing on demand.

Unfortunately, it is really quick to zero a page, because of the dcbz instruction, which invalidates cache-lines without having to touch memory. This instruction has a 1 cycle latency so for 4kb pages, they can be zeroed in 32 cycles. Unfortunately the instructions to get the DMA engine to zero pages is almost 400 cycles. It was actually pretty encouraging that the overhead was only around 1%, which is really just in the noise.

The really interesting thing would be if they used bigger pages. For example, if you were using 4MB pages, instead of 4kb pages the dcbz aprroach would be slower, and would actually suck more because it would probably require writeback. Hopefully once the Gelato guys will get their super page stuff into the kernel soon.

The afternoon had the excitement of the Linux australia AGM, where it was announced that linux.conf.au 2007 would be held in Sydney. This was followed up by a dinner meeting between the LA and linux.conf.au committees at Table 7.

Dinner drinks were hosted by the Google hiring squad, who basically put a big tab on a bar in the city for us, which basically meant free beer for the whole conference.

For a hastily prepared talk this went pretty well. I demoed the PLEB -- showing off hardware is always good for getting the interested level up. Of course I managed to screw up the demo, by failing to actually turn the external power supply on! There were enough questions to think that people were actually listening to the talk, which is always encouraging.

I have the slides available if anyone is interested.

On Tuesday I attended the miniconf, which was pretty fun. Mark Philips provided a great inspiration talk about why working in the embedded is the cool place to be. Most of the talk focussed on robotics, and had great examples of current robotics stuff.

Paul Campbell from Digeo presented on set-top boxes using Linux. The main interesting thing from this talk was the use of a secure boot loader to get into Linux so people can't ripoff any content stored on the set-top box.

Ian Walters from Trolltech gave an update on Qtopia. This stuff looked kind of interesting, they have basically come up with their own programming environment which totally abstracts away POSIX which is underneath. This would be an interesting system to run directly on top of Iguana.

Yutaka Niibe gave a really cool talk on using a USB hub to control AC devices. In Japan they have a much higher respect than we do here, (they signed the Kyoto protocol after all), and care about things like turning off peripheral devices when they are not in use, so they have USB controlled power cables.

There was a bunch of cool hardware shown off, but probably the most interesting one is the gumstix hardware. It would definately nice to get some of these with L4 running on it.

This year the embedded miniconf was more a microconf and only ran for the one morning. So in the afternoon I went along to the GNOME miniconf, it was really cool to see CryoPID which does process checkpointing in Linux.

Dinner was at the Terrace where they serve beer in 3 litre glass tubes, which have there own taps. Pretty damn cool! The meat is served raw on hot rocks which is a pretty cool idea, but I'm not too sure if serving people 3 litres of beer and then giving them boiling rocks is the best idea!

linux.conf.au will be held at the University of New South Wales, Sydney, Australia in January 2007.

I'm on the organising committee and looking forward to creating an awesome conference next year.

Today I moved my blogging goodness from livejournal across to my own website.