LiveWhatYouPreach

Gstreamer HackFest 2012 in Malaga

2012-02-02T13:13:00.002+01:00

Last week, I attended the GStreamer HackFest in Malaga and it turned out to be a very good decision to be there! First of all, I got to meet my two mentors for the OPW (Jeff and Thibault) and Edward, who first started PiTiVi and work closely with them for 3 days. Also, I got to meet a lot of people working on the porting of several applications to GStreamer 0.11. It was a great HackFest and I thank all the people that made it happen.

Working closely with the other PiTiVi team members, offered me the opportunity to work in a more efficient way (by clarifying many things that seemed to confuse me) and get to feel the team spirit (which is a greeeat power of motivation). Meeting all these people made me demystify what exactly is the challenge and the advantages to come while porting PiTiVi to GES. The challenge is that the development of GES is being done almost simultaneously with the porting, so some features/functions could be still not implemented and the advantages are that after the porting advances, the code of PiTiVi will be cleaner and smarter.

As far as the undo/redo functionality is concerned, the MediaLibrary and Timeline parts are working now fine and I am on the Effect part, which must be finally ok very soon (hope today...).

Quick Description of Modules (PiTiVi) - and do I see them used-

2012-01-19T12:16:00.005+01:00

Core

GLib
low-level - Provides us with the implementation of fundamental types and algorithms. It is a base upon which, everything is constructed.
-In PiTiVi, I see the GLib basic types (gboolean, gchar, gint, gfloat, gdouble etc)-

GObject
With the GObject, GLib provides us with the implementation of an object-oriented framework for C.
-In PiTiVi, I see the gobject functions (http://www.pygtk.org/pygtk2reference/gobject-functions.html)-

GStreamer
A multimedia framework that allows us to do anything multimedia-related. It is very flexible and uses elements
that are packaged in the form of plugins.
These elements can be codecs/demuxers/lmuxer/effects etc.
One set of these plugins are the GNonLin plugins, which are the ones who implement anything related to the logic
of video editing in GStreamer. Mainly, handle the timing of reading different multimedia files.

GES (GStreamer Editing Services)
A library created on top of GNonLin plugins, making the use of GNonLin plugins easier to use. It wraps the
GNonLin elements by offering an API of higher level.

In Pitivi, the GNonLin plugins were used directly, up to now and this is why the porting to GES will facilitate
a lot the design of the project.
So, we are using GStreamer via GES and the most objects used are GES ones (even if they come from GStreamer classes).

UI

GTK+
Toolkit for creating graphical user interfaces. Providing standard widgets and event handling. Based also in GLib.

GooCanvas
One of GTK+ widgets, used for drawing.

All of these components are based in GLib and communicate through it and its signals.

So, if I just want to add quickly GES in the PiTiVi' s wiki diagram (https://wiki.pitivi.org/wiki/Architecture), I would add it here:

Pitivi: Undo / Redo Functionality (GES Porting)

2012-01-13T09:09:00.000+01:00

So, after spending some days "beating around the bush", trying to integrate myself to the project by following the team' s work, getting to understand the backbone of the project' s code, I get deep into my task, the undo/ redo functionality.

Firstly, I thought of checking about the undo/redo philosophy in applications in general, which helped me get what was implemented in Pitivi_0.15, undo/redo with a stack approach: (en gros) Having an undo stack where every action taken by the user is logged and saved, so every time he wants to return to the previous state, the undo stack is popped. For redo also, the current state is being saved into the redo stack, before an undo is being performed. So, if we regretted having "undone", the redo stack is popped and the new current state is pushed to the undo stack.

What helps me a lot in understanding the logic of the undo implementation in pitivi_0.15 is to check the code at this version while the undo is still working. Now, with the new restructurate version of the project though, the undo classes and code are grouped together under a specific /undo folder.

While Thiblahute was helping me to get started with my task, he already gave a patch which enables the undo/redo functionality in the MediaLibrary:

http://git.pitivi.org/?p=pitivi.git;a=commit;h=418f71b3f7805270df760ec10cb5ed0a7027786e

(which had to do with the use of GstDiscovererInfo in the place of PitiviFactory, information that I have but I don't actually understand what it implies, so I should get more informed about it.....Hmm, if there will be things related to that that don' t allow undo to work now).

And now I am looking for the next step which will be the undo in the Timeline.

In order to work better, I am getting used to the debug system, setting breakpoints and even just printing.

First days...

2011-12-29T13:42:00.000+01:00

During these first two weeks of my internship, it has been studying time...
Studying a lot of things useful, about: git (mostly progit.org), python (mostly docs.python.org), gstreamer, ges, video formats generally.

It has been a greeat time learning in detail, how powerful git and python are! I think that sacrificing some time in the beginning to get more general knowledge and confidence is something worth doing, than attacking specific tiny parts of the project. And I am sure that this time "lost", will be compensating us afterwards.

Now, I am focusing in understanding the pitivi project better... I am following the commits and the irc discussions from the pitivi team, which helps a lot and I will be trying to re-enable the undo/redo functionality in the ges-ported version for the beginning.

The beginning is never so elegant, but it is so refreshing and challenging, feeling as a newbie again and again...

Say hi to the other kids, tsinaski!

2011-11-24T18:47:00.001+01:00

-Hi other kids, this will be my blog!

The quest for knowledge, wisdom and originality never stops. Sometimes you think it advances, but then you see that you are only on the wrong way.

When one is about to finish his studies, the professional originality and integrity is really taking a lot of place in his mind (or should... or it just does, in my case) ... I have been studying for a Computer Science bachelor 4 years and for a Computer Science master 2 more years. What I like mostly about it, is the freedom in this field. But freedom is not so ea-eas-sy to find! ("Freedom is impossible, this I know" Madrugada) But I know it is there! I know I can use these things I have been studying for purposes that my heart and mind approve and NOT just design the next processor who will sell as the Devil and make Me Rich!

Ah, ha, ha, ha (Professor Chaos - evil laughing) I know I can do that... (in the future?!)

A very wise Greek (and surely, not only Greek) proverb says: "Never postpone something for tomorrow, if you can do it today". So, let's look towards the open source - free software.

I have been accepted for the Gnome' s OPW internship and I feel so happy to consume my energy, mind-work, back-ache for something that seems such a good idea (between so many baaad ideas I can see in the world around me).

I will be working on Pitivi - video editing software during my internship, which is very appealing, as I will have the chance to work on video formats, python and GUI environment, which is something I have missed (snif) while dealing with hardware in my Master :) This blog will be hosting updates from my work on it.

Bon appetit!

P.S.: YES, I am naive, I live in an utopia and I know. Nice to meet me!