Just some notes about the Net

Learning Natural Interaction

2012-02-01T14:44:00.000Z

Just to say it out loud in the hope someone else is interested in it:

I've been studying and I'm intentioned to write an open sourced Natural Interaction module for OpenNI or libfreenect which is able to do skeleton and gesture recognition.

Ideally and in the *very* long term I'd like to have something very close in functionalities to what the closed sourced NITE is for OpenNI, but to begin with a simple shape or movement recognition module will make me happy.

I don't know anything about the subject, including the basic of image manipulation, but if someone would like to have some fun thinking about it, let's join the forces!

D-Bus eavesdroppers and unicast signals

2011-07-22T13:36:00.001+01:00

There was an interesting issue in D-Bus, related to unicast vs broadcast signals, which led [edit: typo] to a small change in specs and which might be of some interest for D-Bus developers.

Unicast signals are not widely known and probably even less used, but they are possible.
They are useful, for instance, when you need to trigger an action from a single client, among your listeners.

Until some days ago, when a unicast signal was emitted, it was actually received by everyone listening to the signal's interface (unless a strict rule was added, unusual), waking up a number of processes which actually weren't interested in the signal.
Collateral effect, waking up cost apart: those processes might actually consider the signal as they were the actual recipient and take some action upon it. Bad.

Typical rule having this problem is "sender="org.foo,interface=org.bar".
Imagine several clients using this rule to listen to org.foo, but org.foo wanting to send a signal to :1.23 only.
Specifying destination=:1.23 for the signal object didn't really work since no dest=val was specified in the rule, allowing any destination actually matching it and all the listeners to be woken up anyway.

The problem with this situation was fixing the bad behaviour without filter out eavesdroppers, which actually wanted to receive the message even if not for them.

The solution is a sort of "eavesdrop opt-in", as Thiago proposed to add a keyword to DBusMatchRule, "eavesdrop=true|false" which defaults to false and with which the listener declares that it really wants to eavesdrop, enabling it to receive messages (including signals) not meant for it (AKA eavesdropping).
Otherwise any message (again, including signals) with a specified destination won't match a filter with no or different destination. Also a rule with a specific destination won't match broadcast messages.

In other words, by default a match rule filter will match only broadcast messages or the ones specifically for you, unless you declare your very nature of eavesdropper by adding "eavesdrop=true" to your filter rule.

This is a behavioural change and consequently means a small amend to the D-Bus spec for 1.5.x.

It also means that if you maintain some code which acts as an eavesdropper, you should fix the code adding "eavesdrop=true" to your filter.
Note that it's only for 1.5.x branch; adding the "eavesdrop" keyword to a filter sent to a 1.4.x bus will fail as the keyword is not recognized.
An example on how to deal with this change keeping compatibility toward 1.4.x (stable branch) and 1.5.x (devel branch) at the same time is shown by this bustle fix. It checks for the feature presence and prepends the keyword if supported.

Facebook, Google+ and Diaspora (part 2)

2011-07-20T18:52:00.001+01:00

This probable is more a tweet [Edit: typo.Thanks to Robot101 :D] than a blog article, but since my last post was about the same subject, I felt it'd make sense to point this article out.

Its author analysed in a deeper way than what I did what the future looks (or is?) like and, I have to say, that after a bit of time spent on G+, I envisioned pretty much a similar future, reason for which I started following Edd Dumbill on G+ and of Twitter ;)
Also thanks to Zack for mentioning the article.

End of post, I said it was short, didn't I? ... and I made it longer than what originally conceived :)

Facebook, Google+ and Diaspora

2011-07-04T09:50:00.001+01:00

Google+ opened to the small public some days ago, I'm not really going to comment anything about it for now.

The purpose of my post is actually reminding people of another interesting project, Diaspora, which actually fits several of my views over social networking.

I really hope that when Google will release API for its G+, there will be some chance for Diaspora to integrate with it and, most important, an opening for G+ to operate with Diaspora.

Most of us use(d) Facebook, now almost any geek I know is joining G+, some of them rejoicing its advent as an opportunity to leave Facebook for good.
That's not really my intention and I don't think it's the point of the whole social thing.

What about, instead, allowing the whole social sites to inter-communicate, exchanging information and letting users being able to see each other independently of the platform used?

That's clearly not possible so far :-), but it is the reason for which years and years ago (Internet-time rules apply) I got interested in FOAF, last year I crossed my fingers with Diaspora and now I'm doing the same about Google receiving some enlightenment bit and getting the right path about profile sharing.

I'm aware that Google point is to re-factor the whole Google experience around Google Accounts and the profiles associated with them, and the major point of it is making G+ a bigger part of G profiles (if you are a Google Profile user, you'll probably noticed that your profile is now your public view of G+, with your public posts for instance).

My point is: Google is aware that not everyone agrees with Google wanting to extract information from your profile, your habits, etc and some of us is not really using Google 100% for this reason.

Also, Google started the Data Liberation front, so why not taking the next step and allowing people to inter-operate with other open [1] social sites?

The big part of the work is not helping Diaspora evolving and gaining power, IMHO, but pretty much the other way round: helping the idea of inter-communication to be a central point of the social experience: this idea getting stuck in some important and enlightened mind so that a bridge will be offered.

But I'm just a noob in the subject: it's just a foolish idea that has been in my mind for long enough and I needed to express :-D

OpenNI in Debian

2011-06-08T12:53:00.000+01:00

The world of augmented reality is quite fashinating.

I recently got interested into Natural Interaction due to the popularity of Microsoft's Kinect and decided to package OpenNI for Debian.

OpenNI is a framework aiming to making natural interaction transparent to the user/developer, publishing a unified API and abstracting the access to different sensors and modules. Currently it supports some Asus sensors and there is a branch on github supporting also Kinect (which is the one we're packaging).

Some cool projects are already using OpenNI: ROS, PointClouds and OpenCV come to my mind immediately.

We'are working on OpenNI package in the Multimedia Maintainers group on Alioth, the package is still not ready to be uploaded to unstable and upstream has some major problems like the lack of SONAME in its produced library, so some communication with upstream is needed but for preliminary use the packages are in a decent state: OpenNI, PrimeSense Sensor, NITE (non-free).

NITE is a closed source module set for advanced body and scene recognition, unfortunately PrimeSense didn't opensource them, thus I decided to use the same approach of flashplugin-nonfree and write a downloader.

For the sake of completeness, unstable already has libfreenect which purpose is similar but specifically oriented to Kinect.

I am studying both and really hope that in the next future some open source project will make (at least) skeleton and hand recognition available under an open license. People are already working on it, according to Google.

Map Buddy 0.4

2010-08-23T15:12:00.000+01:00

Finally, the past week Alban and I released MapBuddy 0.4

As mentioned in my previous post, now MapBuddy supports Point of Interests from OpenStreetMap.
It stores them in a sqlite3 db using its spatialite extension.

We use OSM XAPI, for which sometimes requests fail and it seems to silently ignore requests for large areas.
We are working on it :-)

"Download POIs" in the main menu will download all the OSM POIs in the shown area, which mean that you need just to centre the area for which you want to download POIs for and it will fetch them for you.
This is the only operation that will need network access and might take quite long time, depending of the size of the area. Remember that OSM dislikes very large area fetching. Please be considerate.

This means that if you're planning to have a trip to a city you don't know, what you need to do is cache its tiles at different zoom level just loading them (some improvements for this step are scheduled) and select "download POIs".

Remember to "Show POIs", which will show some of the most interesting categories (OSM features) and select any of them. Amenity and Tourist are among them. Again, improvements are scheduled.

POIs are hidden at wider zoom levels, to improve map readability on high density areas.

Some more improvements are still needed and will be added soon, in particular about speed issues at startup or when finger-scrolling the map with POIs shown and about UI.

Lot of work is still going on in the offline mode direction, a search for POIs, integration with the evopedia package, better tile caching experience, etc...

Last but not least, I'd like to thank Enrico Zini for his great suggestions!

Spatialite

2010-08-17T11:42:00.001+01:00

Yesterday I uploaded spatialite into Fremantle's extra-devel.

Spatialite itself isn't directly useful to the average Maemo user, but it ca be lot of fun if you're a developer and are interested in GIS.

Spatialite is a sqlite3 extension for geo-spatial data and compatible with OpenGIS, which means you can store any map's nodes (using a OSM nomenclature) into sqlite and use them in your application, with SQL methods that will make easier the management of the node in the map space.

For more info http://www.gaia-gis.it/spatialite/ and http://www.opengeospatial.org/

If you need something more powerful you might give a look at http://postgis.refractions.net/, but this is a bit heavy for Maemo :-p

Soon a new version of Map Buddy will be available, supporting point of interest from OpenStreetMap (theoretically any source) and using spatialite (the reason for which I uploaded it), but I'll write specifically about it in another post.

Telepathy

2010-02-19T20:52:00.000Z

It's a long time I don't update this blog.
In the last months I have been quite busy.

First of all I started working with and on Telepathy, a very cool communication framework.
Specifically I'm writing the Telepathy's logger service, using telepathy-glib.

In the next future I'll write some articles about how to deal with some aspect of Telepathy for Telepathy new users, hoping that people will get in touch and start understanding better how the telepathy framework and more specifically the telepathy-glib binding work.

New employer and relocation

2009-10-27T18:24:00.000Z

Quite lot of things happened in a bit more than a month, among which a job.

Beginning November 9th I'll be employed by the guys of Collabora ltd., in Cambridge, UK.
In some weeks I'll also move there, permanently.

I'll stop to be a consultant and I'll be a permanent full-time software engineer.
Collaborans are cool guys and do cool things :-)
I'd never imagined to drop my self-employee position, I always loved freedom and independence.
This time is different, I think I'll be really OK working with them and I rarely have this impression.

In the next weeks I'll update this blog with some more news ;-)

Projects

2009-09-02T20:29:00.001+01:00

I've just created the "projects" label/tag to indicate all those projects in my head that I'm developing, planning to or would like to develop.

A project page in my site will keep some of them.

Let's start with VoIPAlert: a VoIP (initially only SIP) application that registers to a registrar and receives messages and calls, showing/logging to the user incoming/unattended calls and messages on your desktop.

Events Calendar

2009-08-22T16:09:00.003+01:00

After a while configuring my calendar service (I used to use my Apple's iCal, moving to Google Calendar) I decided to create e calendar for interesting events.

Anyone wanting to advertise or just notify me about an event can contact me, e-mailing any relevant event's details as

Event's full name,with, possibly, official English translation
Dates (start/End)
Place(s)
Official web site (if any) and any other important URL (blog, podcasts, etc.)
Small description (also event's related keywords if any)

Alternatively you can send me an iCal invitation/event with the above details already present.

Preferred events will be about Information Technology, the Internet, technologically important, FLOSS related.

Technical, social, philosophical, etc. events will have the same treatment.

A HTML version of the new calendar is here (iCal).

Consegi

2009-08-21T18:23:00.002+01:00

On next August 26th-27th-28th, in the Brazilian federal capital, Brasilia, will take place the II Congresso Internacional Software Livre e Governo Eletrônico (II International Free Software Congress for E-Government).

View Larger Map

Here the English version of the congress' site.

From the same site, three interesting themes touched during the three days congress:

Free Software Ecosystem: Communities and Colaboration
Social Development, Education and Digital Divide
Policies for Industrial and Technological Development

I might go.

Licensing

2009-08-12T18:42:00.010+01:00

I've just added a Creative Commons license to this blog and my work pages.

I take the occasion to remember everyone to licence his work, independently from the choosen license.

Since my choice went to CC, I'll give some tips on how to use it in your site: read CC Web Integration for general web/net licensing and give a look at the license chooser.

[Update 13/08/2009]

This blog is about notes about the Net, I won't go deeply inside an argument, especially if it has been largely discussed elsewhere in the Net.

But what I can do is trying to give as much as information or pointers to understand or at least let the reader create an Idea him/herself.

So what I'm going to do, and it was missing in my original post is giving a good pointer about what is Creative Commons. It's probably something that most of the readers already know, absolutely not a new thing.

Although, it's a very important piece of information, so I suggest you to investigate about how copyrights (and copylefts) work, starting from this video. Browse the CreativeCommons site, the FSF, OSI and any other site you'll find :-)

[End Update 13/08/2009]

EL CLIC

2009-08-11T20:04:00.006+01:00

As some of you may know, I currently live in Brazil.

Even if I'm (still?) not involved in any Brazilian or Latin American FLOSS, or better Free Knowledge, association, I periodically dig the Net about news, information and events I might be interested in, here in this part of our World.

EL CLIC is the (first) Latin American meeting about free knowledge and licensing. It's a Spanish speakers meeting, at least according to the site. It's not very clear where this event will take place (see update below), anyway REDECON is a Venezuelan network/community.

[UPDATE]

The event will be completely free of charge and held via the Internet, using free technologies (free adaptation of "El evento será totalmente gratuito y se desarrollará enteramente a distancia empleando para ella herramientas tecnológicas libres")

[END of UPDATE]

For the not Spanish speakers a (not mine) translation of the event's description:

During the weeks between September 14 and 30 this year, the First Latin American Encounter on Free Knowledge and Licensing will be held.
The encounter aims at sharing experiences and widen knowledge in regard to these two general, current interest topic lines. The initiative comes from the Knowledge as a Public Good Defense Allies Network (RADECON, Red de Aliados para la Defensa del Conocimiento como Bien Público) who, together with a group of close collaborators, seek to define a common path towards knowledge emancipation and towards Latin American integration from the perspective of a change born inside the legal protection towards liberation.
(…)
Topic lines:
Licensing vs. Patenting
Open educative resources
Free Software and licensing
Free knowledge and education
Techno-politic considerations towards knowledge freedom
The needed sensibilization process leading towards knowledge liberation
Licensing: A vision from an ethical standpoint

Here the original translation, by Gunnar Wolf (from whose blog I knew about this event).

Eclipse, MacOS 1.4 and Java 1.6

2009-08-07T22:35:00.004+01:00

Preparing your development environment to play with Google Wave APIs, you may encounter a major problem, if you're running MacOS 1.4. The lack of Java 1.6, needed by the Wave API - at least now, in future 1.5 will be accepted as well they assure.

What to do?

The most used solution is downloading SoyLatte. http://landonf.bikemonkey.org/static/soylatte/

The install procedure is quite easy, just unpack it where you usually keep your develompent stuff (it ~/devel/soylatte16-i386-1.0.3) and add it to your PATH.

If you want to use Eclipse and Java 1.6, it a bit trickier. One quick solution is to add the JVM as a "MacOS X VM":
Eclipse->Preferences then go to Java->Installed JREs and add a new JRE, chose "MacOS X VM", chose the path where you installed SoyLatte, and it's done.

BUT: This way has a major issue, it may break things, as and builders. So, if you cannot add your SoyLatte installation as a Standard VM, it means that this bug is still around.

The best way, so far, is to recompile Eclipse patched.
To not write again and again the same things, I just point to an article explaining how to do it quite clearly: Eclipse, OS X, and SoyLatte.
Unfortunately for Eclipse Ganymede users, it works only for Europa version.

Google Wave

2009-08-02T16:48:00.004+01:00

I got back home, after some days of vacation, finding in my mailbox a message by Mr. Wave, they authorised my sandbox account!

Finally.

Debian network installation

2009-07-23T18:20:00.002+01:00

What are you going to do if you are in your client’s provider’s Data Center, you have to reinstall some Linux servers and you cannot posticipate the installation (the only available day for your client is today) … but you found out that every CDROMs on your servers are broken?

Simple: use the network installation method present on any good distribution: you do the work, your client’s happy and you are happy consequently.

Anything you need is a Internet connection to download the boot files for your distribution and complete the installation, your linux servers (to be reinstalled) and a server on which you’ll install DHCP/BOOTP and TFTP services, which will be reachable by your to-be-reborn servers.

I used Debian GNU/Linux, with installation images from its netinst method. Specifically, the netboot.tar.gz contains anything you need to be used to install Debian via TFTP.

Download it, install dhcp3-server and tftpd-hpa packages.

Enable tftpd service in /etc/default/tftpd-hpa and remember the directory set in the OPTIONS variable.

Let’s go on with the TFTP repository setup: put in the directory specified in /etc/default/tftpd-hpa (usually /var/lib/tftpboot for the tftpd-hpa package) the content of the downloaded tarball:

yourserver:~# cd /var/lib/tftpboot
yoursever:/var/lib/tftpboot# tar xvzf netboot.tar.gz

Configure your DHCP server to work with PXE (/etc/dhcp/dhcpd.conf). Backup the default debian conf and use the following instead:

option domain-name-servers 192.168.10.254;
default-lease-time 86400;
max-lease-time 604800;
authoritative;
subnet 192.168.10.0 netmask 255.255.255.0 {
range 192.168.10.1 192.168.10.10;
filename "pxelinux.0";
next-server 192.168.10.254;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.10.255;
option routers 192.168.10.254;
}

Let’s analyze the above configuration:

First of all, the server IP of this example is assumed to be 192.168.10.254, change it according to your network.
You need to change domain-name-servers option to your current DNS IP(s). You’ll be able to find them in your /etc/resolv.conf file. In this example the server is acting as a DNS too, it couldn’t be your case.

Then you’ll need to choose a network DHCP will offer IPs from. In this example 192.168.10.0/24 (subnet + netmask keywords).
Within this network you can select a range of IPs you can assign via DHCP, in this example the DHCP server is able to assign 10 IP addresses, from .1 to .10 .

Change the range according to your network, choosing the range in a way it doesn’t conflict with existent IPs (ie the current server).

If you change the network (192.168.10.0/24) remember to change any other occurrence in the example.

Filename is the file DHCP will send to the dhcp client, to start the remote boot procedure (PXE: Preboot eXecution Environment). You’ll find this file in the netboot.tar.gz you downloaded.

Next-server is your TFTP server, the server the client will contact next.
It can be any server in your network (or outside), but in our case it is the same of the DHCP server: 192.168.10.254

Last, set there your gateway IP (option routers), since the installation scripts will need to download via the Internet any packages needed. In our example the server is also our default gateway, so client will use it to access to the internet. This option very depend on your network.

Now restart DHCP and TFTPD services and it is ready: just boot your servers, set in their BIOS the boot from network option, reboot with the BIOS modifications and start the installation process.

Once installed any server you need, remember to disable the network boot from their BIOS.

Remember also to shutdown the DHCP and TFTP services after the installation, for security reasons and to avoid problems with any other bad configured BIOS in the net: if a server with a non-disabled network installation in its BIOS will boot and your DHCP serve is still serving your network, this server will reboot with the installation scripts instead of with the real kernel.

Moving to blogspot

2009-07-23T18:16:00.003+01:00

I decided to move to blogspot.
It's not a news, I like cloud programming, I like interconnected services (gmail, gtalk, blog, reader, maps, etc) using the same user base, since I think that nowadays it's the only thing a serious service provider should do.
Google actually does it all, and in a brilliant way, I think.

Thus my choice to use Google's blogspot instead of the old wordpress instance on a server of mines.

To start with, I'll post an old article I wrote about linux network installation, originally on my previous blog (to be disabled soon).