Opensource
libacr published on PyPI
Wednesday, July 28th, 2010 | Computer Science, Opensource, Software Development, Web | Comments
As we are moving to make libacr a very cool and functional python CMF, we published libacr on PyPI!
Now you just need to:
pip install libacr
and you are done, as easy as saying!
More details on http://pypi.python.org/pypi/libacr/
ACR plugins and themes
Tuesday, July 27th, 2010 | Opensource | Comments
Recently we decided to move our Turbogears 2 CMS, ACRCMS, from an example of how to use libacr to something more complete. Consequently to this decision we implemented the plugins architecture inside libacr, which permits to add plugins to libacr at run-time.
Until now there were no real plugins, the only available plugins were the three acr slice templates which have been moved from an internal function to a plugin.
Today the first real plugin for ACR has been pushed in a separate branch, the plugin is the Theme engine, which permits to add theme support to ACR. The plugin is available inside the ACRCMS acr_plugins directory and is now loaded by default by ACRCMS, it will be officially part of ACRCMS in the next release.
We decided to distribute it with ACRCMS instead of libacr as we felt that theme management is a function deserved to a CMS, not to a CMF.
For now you can test it from the themable branch of ACR
GCC using C++
Monday, May 31st, 2010 | Opensource, Software Development | Comments
I got this news http://gcc.gnu.org/ml/gcc/2010-05/msg00705.html and it puzzled me a bit: you have the system C compiler depending on C++, making in fact it no more self hosting.
That alone makes me thing whoever decided and whoever requested that is next to suicidal. GCC is known for having _quite_ a shaky C++ standard library AND ABI, as in having at least an incompatibility every major version and sometimes even with minor ones.
I do dislike C++ usage mostly on this basis, let alone the fact is a language overly large, with not enough people dabbling it properly, let alone being proficient.
There are already compilers using C++, one that many people find interesting is llvm. It doesn’t aim to be a system compiler and it’s not exactly self hosting.
Many already stated that would switch to llvm clang front-end once it reaches full maturity (now freebsd proved that this level has been pretty well archived), I didn’t consider to fully switch to it just because it concerned me the fact it depends on C++ and how easy is to have subtle yet major breakages in that language implementations.
llvm people look to me way more capable of managing C++ than GCC ones and I saluted with please the fact they already have a libc++ implementation.
Back about being suicidal, if I have to pick between people that did well on C++ and people that botched many time on the same field, who would I pick?
The current discussions in the GCC mailing list are about C++ coding style, which features to pick and which to forbid, rearchitecture the whole beast to use a “proper” hierarchy and such, basically some/(many?) want to redo everything with the new toy. That makes me think again that llvm will be a better target for the next months/year.
I hope there are enough GCC developers and/or concerned party that will fork gcc now and keep a C branch. Probably having a radical cleanup and refactor is a completely orthogonal issue and should be done no matter they’ll pick C++ or C as their implementation language, GCC has lots of cruft, starting from their bad usage of the autotools.
Ogg vs World (as picked up from Slashdot)
Wednesday, April 28th, 2010 | Multimedia, Opensource | Comments
Ogg had been discussed a lot lately. Having messed a bit with it and having felt the pain about dabbling with it and with vorbis and theora probably I could chip in.
I said “a pain”, quite subjective and I think the term summarizes my overall experience with it. If that’s because it is “different”, “undocumented” or just “bad” is left to you readers to decide. Even messing with NUT hadn’t been this painful and NUT is anything but mature. Now let’s go back digressing about Ogg. Mans stated what he dislikes and why, Monty defended his format stated that his next container format will address some of shortcomings he agrees are present in Ogg. Both defense and criticism are quite technical, I’ll try to say why I think Ogg, as is, should not considered a savior using more down to earth arguments.
Tin cans, class jars, plastic bottles… Containers!
Lets think about something solid and real. If you consider a container format and a real life storage you might see some similarities:
- Usually you’d like the container to be robust so it won’t break if it falls
- You’d like to be able to know which is its content w/out having to open it
- You’d prefer if weight as less as possible if you are going to bring it around
- You’d like to be able to open and close it with minor hassle.
- If it has compartments you’d like that those won’t break and that picking and telling apart what it contains as easier as possible.
There could be other points but I think those are enough. Now let’s see why there are people that dislike Ogg using those 5 points: robustness, transparency, overhead, accessibility and seekability
Robustness
I think Ogg is doing fine about robustness, the other containers are fine as well in my opinion.
Transparency
In this case the heading is a bit strange so let me explain what I mean. If you think about a tin can or a glass jar usually you can figure out better what’s in a transparent container than in an opaque one, obviously you can have labels with useful information. Usually you feel better if you can figure out some details about the content of a can even if you don’t know how to cook it.
In Ogg in order to get lots of data that the other containers provide as is you need to know some intimate details about the codec muxed in. “What’s the point of knowing them if I’m not able to decode it?” is an objection I saw raised on Slashdot comments. Well, what if you do not want to DECODE it but just give information or serve it in different way, you know actual streaming ー not solutions based on HTTP ー? (e.g Feng and DSS to name a couple).
Overhead
People likes plastic bottles over glass ones since the latter are heavier. When you move and store them that’s an actual concern.
Monty states that Ogg with a recent implementation of the muxer (libogg 1.2) the overhead in Ogg is about 0.6-0.7%, Mans states that it ranges between 0.4% and 1% usually nearer to the 1% than the 0.4%. So in my opinion they agree. How does that value fares with other containers? Mans states that the ISO mp4 container can easily archive about a tenth of the Ogg overhead. Monty went rambling about lots of different container stating some depressing numbers and discussing about random access on remote storage over HTTP and other protocols that are not meant for that.
I think that’s a large degree for improvement, or at least some benchmarking are required to see how that is true or false.
Accessibility
As in “which tool I need to use them?”. Ogg has some implementations, some even in hardware, Mans states that in some situations (e.g. embedded/minimalistic platform) isn’t the best choice. Monty states that similar problems would be there also for the other containers.
As I stated before in order to be able to process an Ogg you need to be able to decode or at least have a knowledge of the codec that nears the ability to fully decode. That means that you cannot do some kind of processing that in other containers doesn’t require such quantity of code and, to a degree, such CPU resources. Being able to do a streamcopy or to pick just a range among a content shouldn’t require decoding ability, those features are quite nice when you do actual streaming.
Seekability
Mans thinks the Ogg ability to move to a random offset within the media has a great degree of issues some related to the mentioned before requirement to know a lot about the codec inside the container other due the strategy in use to actually find the requested offset within the file. Monty goes again rambling about access remote files using HTTP and on how the other containers aren’t that better. The Slashdot article is already full of people stating that they DO feel seeking in Ogg SLOW, no matter the player and kills Monty arguments alone.
In the end
Obviously nothing is perfect and everything is perfectible. I do not like Ogg, I’m not afraid to state it.
Quite often you get labeled as “evil” if you state that or, god forbid, say that Theora isn’t good enough and maybe if you are that concerned about patents mpeg1 is the way to go since the patents are expired.
I’m quite happy with mkv and mov, probably I’ll use NUT more if/once it will get more spin and community. I’ll watch with curiosity how transOgg will evolve.
PS: I liked a lot this comment, Monty do your homework better =P
VideoLAN Web Plugin: xpi vs crx
Tuesday, April 27th, 2010 | Hardware, Opensource, Software Development, Uncategorized, Web | Comments
One of the main issue while preparing streaming solution is answering the obnoxious question:
- Question: Is possible to use the service through a browser?
- Answer: No, rtsp isn’t* http, a browser isn’t a tool for accessing any network content.
* Actually would be neat having rtsp support within the video tag but that’s yet another large can of worms
Once you say that you have half of your audience leaving. Non technical people is too much used to consider the browser the one and only key to internet. The remaining ones will ask something along those lines:
- Question: My target user is
a complete idiottechnically impairednaive and unaccustomed and could not be confronted with the hassle of a complex installation procedure, is there something that fits the bill? - Answer: VideoLAN Web Plugin
Usually that makes some people happy since it’s something they actually know or at least they have heard about. Some might start complaining since they experienced an old version and well it crashed a lot. What would you be beware of is the following one:
- Question: Actually I need to install the VideoLAN Web Plugin and it requires attention, isn’t there a quicker route?
- Answer: Yes xpi an crx for Firefox an Chrome
Ok, that answer is more or less from the future and it’s the main subject of this post: Seamless bundling something as big and complex as vlc and make our non tecnical and naive target user happy.
I picked the VideoLAN web plugin since it is actually quite good already, has a nice javascript interface to let you do _lots_ of nice stuff and there are people actually working on it. Additional points since it is available on windows and MacOSX. Some time ago I investigated how to use the extension facility of firefox to have the fabled “one click” install. The current way is quite straightforward and has already landed in the vlc git tree for the curious and lazy:
<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:em="http://www.mozilla.org/2004/em-rdf#"> <Description about="urn:mozilla:install-manifest"> <em:id>vlc-plugin@videolan.org</em:id> <em:name>VideoLAN</em:name> <em:version>1.2.0-git</em:version> <em:targetApplication> <Description> <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id> <em:minVersion>1.5</em:minVersion> <em:maxVersion>3.6.*</em:maxVersion> </Description> </em:targetApplication> </Description> </RDF>
Putting that as install.rdf in a zip containing a directory called plugins with libvlc, it’s modules and obviously the npapi plugin does the trick quite well.
Chrome now has something similar and it seems also easier so that’s what I put in the manifest.json:
{ "name": "VideoLAN", "version": "1.2.0.99", "description": "VideoLan Web Plugin Bundle", "plugins": [{"path":"plugins/npvlc.dll", "public":true }] }
Looks simpler and neater, isn’t it? Now we get to the problematic part about chrome extension packaging:
It is mostly a zip BUT you have to prepend to it a small header with more or less just the signature.
You can do that either by using chrome built-in facility or by a small ruby script. Reimplementing the same logic in Makefile using openssl is an option, for now I’ll stick with crxmake.
Then first test build for win32 are available as xpi and crx hosted on lscube.org as usual.
Sadly the crx file layout and the not so tolerant firefox xpi unpacker make impossible having a single zip containing both the manifest.xpi and the install.rdf served as xpi and crx.
by the way, wordpress really sucks
ACR got support for user permissions
Wednesday, April 7th, 2010 | Opensource | Comments
ACR opensource Turbogears2 CMS got support for user permissions to allow users to edit only some pages and create children only in some sections. This should permit to separate work between multiple people in ACR based sites.
ACR also got support for blog/news slice template. This permits to create blogs in ACR with just two clicks instead of having to declare the ACR slicegroup youself.
As usual you can download ACR from http://repo.axant.it/hg/acr by using mercurial
Remote desktop, meet multimedia; school, meet remote desktop
Wednesday, February 17th, 2010 | Opensource | Comments
Recently we got contacted about crafting some kind of solution for remote participation to school lesson. Hospitalized students may have hard time catching up and the current technologies, even the overpriced and underused “interactive blackboards” may help a bit in the picture.
What’s an “interactive blackboard” ? It is more or less a projector and any kind of tracking pointer, usually the IR flavour you can see in wide use through the Nintendo Wii. Not exactly a breakthrough it’s something you could craft with about 50e of components and any price for a projector (like the relatively inexpensive and highly portable ones from 3m). You might have some “value added software” that give you an UI that is more “blackboardish” than your standard desktop but that’s all.
How is it used during lessons? Pretty much like a normal blackboard, worst case you have a dumb teacher feeding his poor students dull slides made not so well.
That said it gets pretty easy think about a way to keep the hospitalized student and the rest of the class linked: put a remote desktop solution (nx, vnc, whatever) on the system wired to the blackboard and arrange some controls so that the teacher could give and take the “chalk” to the remote student.
Simple enough isn’t it?
Problems:
- What if the teacher would like to see and heard the remote student?
Well there is plenty of streaming solutions (I’m eyeing sip-communicator currently since they really put a great show at Fosdem, but ekiga or skype could do as well).
- What if the teacher starts to use the “interactive board” to show a DVD and wants the remote student enjoy it?
Ok, there we have a problem, having a large surface updated quite often and asking to have a _good_ quality and expecting the remote student having just a wireless link like umts, edge, gprs is getting really painful.
There are some solutions that have some heuristics in place to discover when a surface is holding a video and they try to compress using some not-so-lossy and quite-enough-low-delay. A bit suboptimal but should work somehow. I wonder if somebody has already thought about harnessing XV, XvMC and libVA capabilities and try to wire the not so fully decoded bitstream this way. Given you have a vaapi implementation on both endpoint and the right codec you may get a perfect movie and probably also spare some bandwidth. If I’ll have time probably I’ll try to have a proof of concept using the efikamx as endpoint, given it will get a vaapi bridget to it’s hardware accelerators.
For the audio you can compress it quite well w/out many complaints and wiring it from a desktop to another is relatively easy (hi, pulse!).
So I already described some months of work, now the last problem:
- What if I want many remote students interact with the same class and blackboard?
Ops. Given the class may have a link that’s no better than umts as well if we are talking about bare remote desktop might be feasible
If we could cut the video feeds and keep just the voices of the remote students we could still survive with 3-4 at most
If we want them to enjoy the video the teacher is about to show to the classe then… we need something else, completely. The whole blackboard&such software could stay better on a server with enough bandwidth and cpu to serve all the remote nodes with ease. Also the class could use a thin client wired to the interactive blackboard and more or less everybody could be happy. Sadly such technologies aren’t that ready. There is spice that’s quite promising, but not ready yet.
That’s all for now, I spent enough time rambling. We’ll see if this “cloud”y ideas will end in an implementation or not. And I haven’t started yet thinking about which software would run on this contraption… Anybody has a any experience with educational software for middle/high schools?
Rehearsing new ACR look and feel
Tuesday, November 24th, 2009 | Opensource, Web | Comments
As some turbogears projects are starting to use ACR as their CMS library we received the first few requests by real users and the most prominent one is to have a better administrative section. Currently administration section is implemented by using the great tgext.admin and sprox, even if those are really good to quickly implement a CRUD section they might not couple very well when a more interactive and advanced user experience is required.
So a transition phase that will end with a totally new administration section for ACR has been started, currently the system implements a new user interface still using the same backend as before to handle the operations, but on the long time the backend itself will be rewritten to handle easier contents creation and management. In the mean time also support for multi-language, versioning and authors has been added.
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- ACR New Dashboard
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- ACR New Page Management
ACR divided in ACRcms and libACR
Friday, August 21st, 2009 | Opensource, Web | Comments
As new projects started to use ACR to implement the content management part of the site we started to divide the ACR application from the content management framework to permit to other people to embed the cmf inside their own applications.
Now has been divided in libACR which is the content management framework and ACRcms which is the cms application. This should make easier to use libACR to implement your own CMS or extend your web applications and also fast for anyone who needs a quickly available CMS solution to just use ACRcms and tune the graphic theme and layout.
ACR got Google Maps view support
Wednesday, July 15th, 2009 | Opensource, Web | Comments
We have recently put inside the ACR svn the support for the GMap view, this means that now you will be able to display both static and dynamic google maps by using ACR.
Using MapView is as simple as specifying the location to display and set map as the view of the slice.