Install ffmpeg for alembik transcoding server with 51.40.4 on ubuntu

I find the alembik transcode server a cool piece of software, but I found lots of caveats when started to use it.

The most difficult part is that alembik supports only two versions of libavcodec for ffmpeg, so you must compile it from the sources, since they are quite old.
That happens because ffmpeg changes the parameters from version to version and the alembik team had choosen both 51.40.4 and 51.48.0 to be supported. I think that in the future it will be possible to have an external “.properties” file, so I hope that it will not be necessary to compile ffmpeg by hand, every time.

I’ve used this references:
http://sourceforge.net/mailarchive/message.php?msg_name=48A176CC.8080300%40kimiasol.com (here i’ve found the rpm of a ffmpeg with libavcodec version 51.40.4 to download)
http://juliensimon.blogspot.com/2008/12/howto-compiling-ffmpeg-x264-mp3-xvid.html (this post teach how to install libamr from mediubuntu repository)

install both amr, you can install also from mediubuntu repo.

wget http://ftp.penguin.cz/pub/users/utx/amr/amrnb-6.1.0.4.tar.bz2
wget http://ftp.penguin.cz/pub/users/utx/amr/amrwb-7.0.0.1.tar.bz2
# apt-get install g++ nasm zlib1g-dev libx264-dev libfaad-dev faad liba52-0.7.4-dev libgsm1-dev libmp3lame-dev \
libtheora-dev libvorbis-dev libxvidcore4-dev libfaac-dev libimlib2-dev libfreetype6-dev

Use an aplication to convert the rpm to tar and decompress it (with alien or something else):

# wget http://dag.wieers.com/rpm/packages/ffmpeg/ffmpeg-0.4.9-0.9.20070530.rf.src.rpm

# ./configure --enable-libmp3lame --enable-libogg --enable-libvorbis --enable-libamr-nb --enable-libfaad --enable-libfaac \
--enable-libgsm --enable-xvid --enable-x264 --enable-liba52 --enable-liba52bin --enable-pp --enable-shared --enable-pthreads \
--enable-libtheora --enable-gpl --disable-strip --enable-libfaadbin --prefix=/usr/local --enable-swscaler --enable-libamr-wb

Install it as a package or with “make && make install” and settup alembik with “ffmpeg.version=51.40.4″

How to correctly make Javascript onclick links and keep in mind SEO and compatibility

Today I have faced a common problem with web developers: How to correctly make Javascript onclick links keep in mind SEO and compatibility.

My solution was very simple, first of all, never use:

<a href="javascript:void(0)" onclick="some_function('someparameter')">Text</a>


This is the worst way of having javascript links. As discussed in this post this is a known issue of IE and why the use of the javascript pseudo-protocol for the value of HREF attributes is actively discouraged.

Suppose that you have an ajax box with tabs that allows you to refresh the content of the tabs with ajax. What would be the best way of assign onclick events to refresh the content with ajax?

What I did was:

• When the page is loaded the first tab is loaded in the server side, without ajax. In this way search engines can crawl the contents.
• The link on the tabs points to the HREF of the current page with a parameter that permits to change the pre-selected tab in the server side when the page is loaded. Ex: ?sec=onlineusers loads the page with the tab of onlineusers pre-selected and ?sec=lastusersers load the page with lastusers pre-selected.
• The link on the tabs have the event onclick associated with a function and it returns false.

Code speaking:
<a href="?tabselection=onlineusers" onClick="changeTab('onlineusers');return false;">Online Users</a>
<a href="?tabselection=lastusers" onClick="changeTab('lastusers');return false;">Last registered users</a>

What are the advantages of this solution?

• If the user have javascript disabled he can still have a fully functional website.
• Search engines and mobile phones can navigate without problem.
• It is compatible with all browsers.

For those who have already a website running, the simpliest way of having compatibility is to link the HREF to a page like “/noJavaScriptEnabled.html” and return false in the onclick event. Doing like this seems to be better than use the “javascript:void(0)” or point to the anchor “#”.

new audio toy – terratec dmx 6 fire usb

Today I have “invested” a reasonable amount of money in the Terratec DMX 6Fire USB witch seems to be a very cool toy! It’s engine runs at 24 bits / 192 kHz and promises crystal-clear sound with a with switched 48V phantom power, a -20 dB pad switch and separated gain controls.

Now I just have to find the best software for starting recording. I am very used to Magix Samplitude, but my last recordings with the open source tool Ardour2 under Linux were not bad at all! I hope I can use it easily with Ubuntu Studio.

database replication tools

Today I was searching about “replication architectures” and found a very interesting presentation: Portable Scale-Out Benchmarks for MySQL that refers to GORDA – “Open Replication of Databases“. The following tools are the result of my search on that topic:

ESCADA is a opensource implementation of the GORDA replication server interface. It provides a full range of database replication options across a multiple database management systems, in a single inter-operable and evolutive package. Target application scenarios include:

• Asynchronous master-slave replication, the no-frills industry standard approach.
• Consistent multi-master/update everywhere replication for scalable and high performance shared-nothing clusters.
• Zero data-loss inter-cluster replication over WAN for mission critical applications and disaster recovery.

–

SEQUOIA is a database cluster middleware that allows any Java application to transparently access a cluster of databases through JDBC. You do not have to modify client applications, application servers or database server software. You just have to ensure that all database accesses are performed through JDBC.

SEQUOIA allows to achieve scalability, high availability and failover for database tiers. It instantiates the concept of Redundant Array of Inexpensive Databases (RAIDb). The database is distributed and replicated among several nodes and SEQUOIA load balance the queries between these nodes. The server can be accessed from a generic JDBC driver, used by the clients. The client drivers forward the SQL requests to the SEQUOIA controller that balances them on a cluster of replicate d databases (reads are load balanced and writes are broadcasted).

–

Slony-I is a “master to multiple slaves” replication system supporting cascading (e.g. – a node can feed another node which feeds another node…) and failover.

The big picture for the development of Slony-I is that it is a master-slave replication system that includes all features and capabilities needed to replicate large databases to a reasonably limited number of slave systems.

simple script to merge commits from a bugzilla id

Today i have made my first PERL script!

For me it is very painful when it arrives the time to merge, into another branch, all the commits that i have done in the “trunk”. I have searched a little and did not find anything that could magically solve all my problems. I know that it’s better to create a separated branch when there are lot’s of commits, but there are some cases that a super-simple functionality can explode into a big ball of mud.

Practically the script merge all the commits of a bugzilla id to another branch. If someone knows a standard way to do this; please tell me!

The script take three inputs:

1. The starting revision ID to filter the search.
2. The SVN address of the source.
3. The search string to filter the results. Here you put your bugzilla bug id.

Commands that are executed when you launch the script:

1. Go to the directory of the destination branch.
2. To execute the script simply do:
3. svn_search_merge.pl 0 https://svn.example.com/main/trunk/ “1: “
4. Note that “1: ” is the bugzilla bug id. What happens next is:
5. svn log -r 1:HEAD https://svn.example.com/main/trunk/
6. With that command we get the log of all commits from the revision 1 to the HEAD. After it’s just matter of check if the string “1: ” is inside the log. Then we simply execute:
7. svn merge -r (ACTUAL_REVISION-1):ACTUAL_REVISION https://svn.example.com/main/trunk/

Source code of the script:

#!/usr/bin/perl

# Simple script to merge commits from a source branch to the current destination directory.
# http://mufumbo.wordpress.com/2008/05/10/simple-script-to-merge-commits-from-a-bugzilla-id/
#
# Example:
# $ cd my-branch-destination/
# $ svn_search_merge.pl 3000 https://svn.example.com/main/trunk/ "bug 673"
# Where 3000 is the starting revision and "bug 673" is the string to match in the comments.
#
use strict;
use warnings;

my $prev_revision = shift;
my $svnHost = shift;
my $searchStr = shift;

print "Starting Revision: $prev_revision\n";
print "SVN addr: $svnHost\n";
print "Search pattern: $searchStr\n";

my $buffer;
$buffer = `svn log -r $prev_revision:HEAD $svnHost`;
my $shouldContinue = "y";
LOGS: foreach my $changelog_entry (split(/----+/m, $buffer)) {
	if($changelog_entry =~ m/($searchStr)/) {
	        #my (undef, $info, undef, $comment) = split(/\n/, $changelog_entry);
	        #next unless $info =~ m/^r/;

		print "\n--------------------------------------------------";
		print $changelog_entry;
		my $revisionId = substr($changelog_entry, 2, 5);
		$revisionId =~ s/^\s+//;
		$revisionId =~ s/\s+$//;

		if ($shouldContinue ne 'a') {
			PROMPT: while(1) {
				print "\nShould continue with merge of revision '$revisionId'? (Yes,Always,Skip,Exit): ";
				$shouldContinue = <>;
				chomp($shouldContinue);

				last PROMPT if $shouldContinue eq 'y';
				last PROMPT if $shouldContinue eq 'a';
				next LOGS if $shouldContinue eq 's';
				die("User requested to stop.") if $shouldContinue eq 'e';
			}
		}
		else {
			print "\nAuto merging '$revisionId'\n";
		}

		my $pRevisionId = $revisionId-1;
		my $mergeBuffer = `svn merge -r $pRevisionId:$revisionId $svnHost`;
		print $mergeBuffer;
	}
}