Herostratus’ legacy

Personal notes — 1 comment
06
Oct 09

GIT quick notes

I want to work on a new plug-in inside of gst-plugins-bad. But also I want to expose my development to a personal GIT repository, so my friends could fetch my changes.

As Linus Torvalds explained once keeping a nice linear regression set of patches above an upstream development implies the use of git-rebase, nevertheless that also implies that I will have to force my pushes and my friends will also have trouble keeping their repositories in sync with mine.

So this is a kind of compromise between be nice with the people who pull your changes, or ease your daily work.

Planet Igalia — No comments
19
Sep 09

libgoo & gst-goo

Back in 2007 I started to work integrating OpenMAX IL components into the GStreamer platform.

OpenMAX is a set of programming interfaces, in C language, for portable multimedia processing. Specifically the Integration Layer (IL) defines the interface to communicate with multimedia codecs implemented by hardware or software.

Texas Instrument started to work on an implementation of the OpenMAX IL for their DSP accelerated codecs for OMAP platform.

A quick and rough view of the software architecture implemented to achieve this processing is more or less exposed in the next diagram:

+---------------------+
| OpenMAX IL          |
+---------------------+
| libdspbridge        |
+---------------------+
| Kernel (DSP Bridge) |
+---------------------+

The DSP Bridge driver is a Linux Kernel device driver designed to supply a direct link between the GPP program and the assigned DSP node. Basically the features offered by the driver are:

Messaging: Ability to exchange fixed size control messages with DSP
Dynamic memory management: Ability to dynamically map files to DSP address space
Dynamic loading: Ability to dynamically load new nodes on DSP at run time
Power Management: Static and dynamic power management for DSP

The libdspbridge is part of the user-space utilities of the DSP bridge, which purpose is to provide a simple programming interface to the GPP programs for the driver services.

In the DSP side, using the C/C++ compiler for the C64x+ and the libraries contained in the user-space utilities, it is possible to compile a DSP program and package it as a DSP node, ready to be controlled by the DSP bridge driver. But right now TI provides a set of out-of-the-box DSP multimedia codecs for non-commercial purposes. These nodes are contained in the tiopenmax package.

So, as I said before, my job was to wrap up the OpenMAX IL components delivered by TI as a GStreamer plug-in. In that way a lot of available multimedia consumers could use the hardware accelerated codecs. But also, our team did the test of the delivered OpenMAX components.

After trying several approaches we came to the conclusion that we need a new layer of software which will provide us

Facilitate a great testing coverage of the components without the burden of the upper framework (GStreamer in this case).
Improve the code reuse.
Use an object oriented programming through GObject.
Facilitate the bug’s workaround for each component and maintenance of those workarounds.
A playground for experimenting with features such as (OpenMAX specific) tunneling and the (TI specific) DSP Audio Software Framework (DASF).

For those reasons we started to develop an intermediate layer called GOO (GObject OpenMAX).

+---------------------+
| GStreamer / gst-goo |
+---------------------+
| libgoo              |
+---------------------+
| OpenMAX             |
+---------------------+

libgoo is a C language library that wraps OpenMAX using GObject. The follow diagram shows part of its class hierarchy.

                           +--------------+
                           | GooComponent |
                           +--------------+
                                   |
+---------------+ +---------------+ +---------------+ +---------------+
| GooTiAudioEnc | | GooTiAudioDec | | GooTiVideoDec | | GooTiVideoEnc |
+---------------+ +---------------+ +---------------+ +---------------+
        |                 |                 |                 |
 +-------------+   +-------------+  +---------------+ +---------------+
 | GooTiAACEnc |   | GooTiAACDec |  | GooTiMpeg4Dec | | GooTiMpeg4Enc |
 +-------------+   +-------------+  +---------------+ +---------------+

At the top there is GooComponent which represents any OpenMAX component. If the OMX IL implementation is neat and clean, there shouldn’t need to add subclasses underneath it, just parametrize it, and should be ready to use as any other OMX IL component. But reality, as usual, is quite different: Every implementation is different from each other; and to make it worst, each component in a same implementation might behave differently, and that was the case of the TI implementation.

Finally, over libgoo there is gst-goo, the set of GStreamer elements which use the libgoo components. GstGoo also sketched some proof of concepts such as ghost buffers (to be used with the OpenMAX interop profile), and dasfsink and dasfsrc (TI specific).

In those days, before I move to the GStreamer team, an old fellow, Felipe Contreras, worked on gomx, which is the precedent of libgoo, before he got an opportunity in Nokia and started to code on GstOpenMAX. An interesting issue at this point is that Felipec is pushing boldly for a new set of GStreamer elements which ditched OpenMAX and talks directly to the kernel’s DSP bridge: gst-dsp.

What’s the future of libgoo and GstGoo? I couldn’t say. Since I moved to Igalia, I left its development. I’ve heard about a couple companies showed some kind of interest on it, sadly, the current developers are very constrained by the TI workload.

Planet Igalia — No comments
24
Aug 09

misc

Do you remember that I promised not to use a minimalistic window manager? Well, sorry, another broken promise. Since I started to play around with imapfilter, I discovered lua. Moreover, a comment in a previous post made a mention of awesome, a minimalistic window manager configured through lua. So, I installed it, play with it, and suddenly I got delighted with all of its features: Awesome comes along pretty well with Gnome and its panel, which I didn’t want to lose at all. Besides, Awesome provides its own panel (called widget box, a.k.a. wibox), which includes a systray (sadly, awesome’s systray steals the icons from the gnome-panel’s systray). I’ve found that a tidy desktop, which avoids to the user unnecessary mouse interactions, is much more relaxed and helps the user to focus on her task. We’ll see how this experiment ends.

Meanwhile, Joaquin, a colleague from Dextra, told about they were having troubles with the gst-openmax JPEG decoder element, because it needed a JPEG parser, while the gst-goo one mimic the official JPEG decoder provided by GStreamer in gst-plugins-good. In other words, the last two elements actually parse the buffer and validates the presences of a complete image in a single buffer, while the first doesn’t, it just assumes it, relying thou on a parser after the data source, which will deliver the image meta-data through fixed capabilities in the parser’s source pad.

Loathed by HAM and all the release processes, I though it could be nice to wet my feet again in the GStreamer waters. Besides, I need to help Iago with his codec base classes, so this JPEG parser, would help me to ramp up.

As an historical note, the first element I took in charge when I get in the GStreamer development group in Dextra was, precisely, the JPEG decoder.

As soon as I chatted with Joaquin, I found a bug report about an element for that purpose, but it still missed a couple features to turn it useful for our needs. And start to hack it. First, I moved from gst-plugins-good, to gst-plugins-bad, and then parse the image header in order to find its properties such as width, height, if the image is progressive, color format, etc. And the set these data in a fixed capability. Also, the frame-rate is negotiated in the sink pad of the parser, such as in the official JPEG decoder.

Finally I got something which seems to work OK and posted it in the same bugzilla report. I hope to receive feedback soon.

On the other hand, I’m still waiting for the approval of my last patches to the GStreamer’s Vala bindings (592346, 592345 and 591979). 591979 can be particularly controversial, given that it changes a typical class method, into a static function. I guess I need to ping somebody.

On the Bacon Video Widget port to Vala, some advances had came, but still there’s nothing to show yet.

Planet Igalia — 1 comment
09
Aug 09

the true imap usage: imapfilter

As I said before, I have been using mutt as my e-mail client, and I’m really getting into it. It does what it is supposed to do, cleanly and fast.

Nevertheless its support to IMAP lacks of several nice features. One I miss the most is to notice the unread messages in all of my IMAP folders. Yes, what it does is to notices the new e-mails, but if you ignore the announcement, Mutt will not remind you those not-yet-read messages later on.

And that was my biggest fear: Have I missed an important email?

Then I found imapfilter, the IMAP Swiss Army Knife. Using the LUA programming language, you would manipulate your IMAP resources as you want: you can do complex searches, apply operations on messages (move, copy, delete), put flags on them, etc.

So, my task was obtain the list of unread messages in my IMAP account. After a few of LUA exploration, I managed to get this script:

server = IMAP {
    server = 'mail.server.com',
    username = 'vjaquez',
    password = 'myubberpassword',
    ssl = 'tls1',
}

mailboxes, folders = server:list_all ('*')
for i,m in pairs (mailboxes) do
   -- server[m]:check_status ()
   messages = server[m]:is_unseen () -- + server[m]:is_new ()
   subjects = server[m]:fetch_fields ({ 'subject' }, messages)
   if subjects ~= nil then
      print (m)
      for j,s in pairs (subjects) do
         print (string.format ("\t%s", string.sub (s, 0, s:len () - 1)))
      end
   end
end

It prints out nicely all the messages I haven’t read, so I can go to those IMAP folders, and read them.

Sadly, there’s no way to integrate (as far as I can see) the imapfilter results with Mutt. But that would be amazing! Imagine an IMAP email client manipulated by commands like these.

And those feelings made me recall the Philip’s ideas about integrating Tinymail with Tracker.

And I wonder, does imapfilter support pipelining?

Planet Igalia / Planet Maemo — 5 comments
28
Jul 09

The SSU nightmare

In the Maemo domain, there’s a concept called SSU, Seamless Software Updates, which is the mean to update the whole operative system without reflashing the device.

This concept is relatively new in the mobile device domain, where reflashing has been the common upgrade path. But this idea is as old as GNU/Linux distributions.

Maemo uses the Debian format packages and dpkg /APT for their handling.

Meanwhile in Debian we are used to the dist-upgrade command in APT to upgrade to the new OS release, in Maemo is not the case because each OS release has a specific hardware target, so there is no need to handle complex dependency handling.

And that is the historical reason that the Hildon Application Manager does not use the APT algorithms for dependency handling. Instead of that, it use custom chicken-like algorithms: if the dependencies are not fulfilled without any foreseen problem, the package installation, upgrade or removal is rejected.

The Maemo OS upgrades are done through a meta-packages, which is merely a list of package dependencies to conform the new release. And this is all the magic in the famous SSU.

But this approach posses a couple drawbacks, which, in Fremantle, had grown disproportionally given the dimensions of the project.

First, the number of packages which conform a new release is so big, that the package section in the list file is bigger than the buffer size allocated by APT to parse it. We already filed a bug in Debian about this matter. It seems the problem is an integer overflow.

Second. It is quite easy to break the SSU process: if you install a third party application with a hard dependency to an OS package, the meta-package of the next release will fail, given the chicken-like nature of H-A-M when solving dependencies problems.

The adopted solution is impose a dependency policy for third party packages, which current implementation had triggered a community discussion.

The other proposed solution, use the tiger-like algorithms available in APT, was discarded given the risk of the needed changes in the apt-worker versus the available time frame.

No, there is not conclusion yet about the third party policy issue.

Planet Igalia — 4 comments
19
Jul 09

lit

Given the Igalia’s OLPI program (One Laptop Per Igalian) I got a new Thinkpad, the x301. I chose this one just because Alex chose it too, and I trust in the Alex judgement, and I don’t regret it: it’s a great machine.

All my computers had receive a name. The first computer I bought with my own resources was named Rowena. I still like that name. My first laptop was named Angelina. Meanwhile my third desktop computer was named Toaster.

So, in order to not break the tradition, I named the new laptop, and its name is lit

lit as noun is the contraction of literature. As adjective is the contraction of illuminated or lighted. Also, in French means bed.

I took a different approach to work with this laptop. First of all, I installed Debian Squeeze on it. Not Ubuntu, nor Gentoo. The reason of this is follow the starndard Igalia’s software stack.

The second difference is an reinforce in my console orientation Instead of using Evolution, I’m trying Mutt; instead of XChat, IRSSI; right now I’m testing Newbeuter as feed reader, all of them in a single terminal using GNU/Screen. Besides, I’m continuing with my Emacs dependency curve.

And, if you’re wondering, I’m not going to use RatPoison or any other minimalistic window manager, and maybe never will.

Here’s a screenshot of my current desktop:

lit-screenshot

Planet Igalia — No comments
14
Jul 09

10 blast moments at GCDS

When Edu played Gimme the power in the Gnome party
When we rented a car to pass an afternoon in Maspalomas
When Owen Taylor showed a picture with me and others as if we were the
authors of GnomeShell
The Robert Lefkowitz keynote
That actually my talk in GUADEC-ES had public!
The girls taking the sun in the beaches
The hacking sessions at hotel’s lobby
Met Jürg Billeter at Collabora’s party
Gossip with Marius
The weather… (it didn’t rain!)

Planet Igalia — No comments
13
Jul 09

GCDS ramblings

The last two years the GUADEC has been pushing the geographical limits of Europe: in 2008 in Istambul, more near to Asia, and now, in 2009, in Canarias, more near to Africa. And that’s OK, I like it actually, is better than repeating the old hosts of the conference.

Comparing my impressions with that two last GUADECs, I found something interesting: In Istambul the new ideas were boiling the environment, bold proposals: the seminal concepts for Gnome Shell, Zeitgeist, Gnome 3.0, and so on. And now, in Gran Canaria, the spirit was an evaluation the development of those ideas, a revision of where the project is and what’s missing to achieve the goals.

In Istambul, the hackers takeoff. In Gran Canaria, the hackers landed.

Nokia stepped back from GTK+ in their products and announced their official support to its recently acquired Qt framework. And that announcement staggered the gnome mobile gang, forcing to rethink their objectives.

The online desktop died and from its rotten corpse a new flower appeared: Gnome Shell: The desktop is a canvas driven by javascript applets, just like the Web 2.0. Moblin also adopted that idea, and many other are going in that path.

The Federico’s crazy idea about a chronological desktop evolved into Zeitgeist, which is taking over as the Tracker user interface for Gnome.

The furor unleashed in Istambul with the announce of the efforts for Gtk+-3.0 had been diminished in this time. Nevertheless, Garnacho showed in the GUADEC-ES some of his unfinished branches, some of them quite amazing, but unmerged into mainstream yet.

Almost of the attention was hogged by Clutter, and the Moblin guys are using this to push the rest of their framework. I guess that everybody is waiting a miraculous merge among Gtk+ and Clutter, but that’s really hard to happen.

Vincent is still pushing for Gnome 3.0. And I really wish for that to happen. And Gnome 3 means GnomeShell, Zeitgeist, and possible Gtk+ 3.0 and GStreamer 1.0. Those new versions doesn’t mean necessary new features, but more clean ups in the code.

What excited me the most was the discussion towards GStreamer 1.0. There’s plenty of work to do. Hopefully I’d find a spot to collaborate on it.

Also I went the ConMan talk and a couple about WebKit, DBus, and a couple more.

Planet Igalia — 2 comments
12
Jul 09

Gran Canaria Desktop Summit

My biggest surprise in the GCDS was in the Owen Taylor’s talk about Gnome shell: he attributed the authoring of Gnome shell idea to Kimmo, Rodrigo, Miguel and myself! and I had no idea! Sadly, I looked in the gnome-shell git repository and I didn’t find any reference to myself. So, no, I’m not an hypnobate coder.

Planet Igalia — No comments
11
Jul 09

My GUADEC-ES talk

Last wednesday I talked in the GUADEC-ES about Vala. A slight introduction to the language. Here are the slides.

Herostratus’ legacywords from a lazy coder