Connecting two computers using a twisted pair cable (or a switch)

Sometimes being able to connect two computers using a twisted pair cable or a switch is extremely useful for copying data.

Once we have plugged the cable in both computers (or we have plugged both cables in the switch), we must assign a new IP address to both machines:

ifconfig eth0 netmask
ifconfig eth0 netmask

To check whether both computers communicate, we must ping each computer from the other one:


It is important to ping always the other machine, because pinging the same address (i.e., from always works.

If no packet has been lost, computers communicate because both can send a receive packets. But to move files, one must select a proper protocol.

For security reasons, during this connection no computer should be physically connected to the net.

When everything is done, we get the default internet connection configuration again by restarting the system or by running as administrator:

/etc/init.d/network restart
Posted in Personal technotes. Comments Off on Connecting two computers using a twisted pair cable (or a switch)

Copying your MBR

To check whether an issue with my laptop’s in-line recording is a hardware problem or a buggy audio driver, the guy from Dell’s technical support asked me to install Windows to discard a software failure. I have been asked to do that after having the mainboard replaced (laptops have no separated sound cards). I have to decrease the size of one of my partitions, create a new one and format it as FAT32.

But the issue here is that Windows will rewrite the master boot record (to promote competition ;-)) when installing it.

I have asked how to restore the original MBR at Mandriva Expert and thanks to the replies, I have a method to copy and restore the MBR.

As administrator, run the following command:

dd if=/dev/sda of=mbrsave bs=512 count=1

To have it back, run as administrator again:

dd if=/path/to/mbrsave of=/dev/sda

Many thanks, George and Jean-Pierre, for the tip.

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On presentation technologies (what Lessig might need)

Reading Lawrence Lessig’s Experiments in presentation technology, I became extremely interested on his efforts when I read:

My hope is to put every presentation I’ve made, with audio and the source files, up for anyone to do with as they wish. That turns out to be harder than it should be. Any advice or help would be greatly appreciated.

It sounds promising, but there is an issue that makes the task harder than it seems:

The only difficult part about this was listening to myself again (and again) as I built this.

If I don’t understand the issue here wrong, the problem is the timeline to sync audio and each slide. It is difficult to guess how long each slide should take. And if you have many slides, this task will be tedious. And a solution for this would be that the computer counts for you.

Computers are mainly counting machines. It should not be difficult to implement a multiplatform program (using wxWidgets or something similar) that is able to detect keystrokes defined by the user to start the timeline, detect each new slide transition and finish the timeline and that is also able to export this timeline into a text file.

An example of this would be a (Keynote/PowerPoint/Impress/PDF) presentation not using the fullscreen mode to see what comes next (or in a mode that enables you to see previous and next slides). You start recording the audio and start the timeline. Each slide transition is detected by the program, so the syncing will be perfect. You finish the timeline and stop recording. The ouput file would be:


(Of course, the program could have another features, but this is only a basic sketch.)

If I’m not wrong, Lawrence Lessig could even generate the timeline when giving the presentation. This would be the first step to generate the presentation with audio in a PDF file (as suggested here).

Posted in Digital typography, Presentation technology. Comments Off on On presentation technologies (what Lessig might need)

On presentation technologies (PDF)

After reading Lessig’s Experiments in presentation technology, I have been searching for a proper way of syncing audio and slides. As far as I know (and I’m not a programer, only a user), vectors are smaller and better for being zoomed than bitmaps. Formats that allow vectors and multimedia are PDF and Flash.

I think PDF is the right answer (my experiences with Flash will be described on a following post). It is both possible to determine the duration of an automatic page display and it is possible to embed audio and video files on PDF files. Both issues are described on the PDF Reference Version 1.6. The /Dur entry to the page object is described on page 121 (and it is rather tricky, since Acrobat/Adobe Reader only advances automatically to next page when the /PageMode /FullScreen is set on the catalog dictionary [although this might not be mandadory]). “Multimedia” is described on section 9.1 of the PDF Reference and I guess that section 9.2 (“Sounds”) is not applicable to mp3/ogg files. (Sorry, but it is too technical for me.)

The question is then which tools can modify already existing PDF documents to set the duration display duration of each page and to add the background mp3/ogg audio file to the complete presentation. Apart from Adobe’s tools themselves, I’m afraid that no tool released under an open source license is able to achive this right now, but I guess there is one that could be easily implemented to do the job.

pdftk is a tool to manipulate PDF documents and it is released under the GNU GPL. It is a command line tool and it runs under Windows, GNU/Linux, Mac OS X, FreeBSD and Solaris. It could be implemented in the following way:

  • Adding an option pagedisplay times.txt, having times.txt the following content:


    Time intervals could also be introduced only in seconds or in hours:minutes:seconds.

  • Switching /PageMode to /FullScreen in the catalog dictionary (it is required for the automatic display to work).

  • Adding an option audiosync audio.mp3 n, where n stands for the page number where the audio file should be inserted. Probably it would be a good idea to allow to insert different audio files in different pages.

If you feel more confortable with Python, I guess pyPDF could be developed to be able do the task, but this tool is in earlier stages of development and probably more labour would be required. Since pyPDF is actually a library and it requires an interpreter to run, it is harder to be deployed by end-users.

On the display side, Adobe Reader 7 is able to deal with both features, but multimedia playing doesn’t work in UNIX. And what about non-Adobe PDF viewers? poppler handles neither the page object entry /Dur (see issue) nor embedded multimedia (see issue) yet.

And eventually the question is: any takers?

Size does matter

Of course, I mean size of audio files (again). Thanks to Cory Doctorow, I found out that the talk Digital Culture in Brazil is available as mp3 file.

And again, the file is huge: 181 MB. After reencoding it with properties set to mono and 32 kbps (method below), the resulting file is only 22.6 MB. I may be wrong, but there is no significant difference between both files. I think the size issue is important not because of the end user, because (s)he can always reencode the file her/himself. It is a question on not wasting bandwith when it is really not required.

I have never lived in Austria, but I lived two years in Germany (not the same country, but Bavaria is very similar to Austria, even more similar than other parts of Germany). And coming from Spain, one of their remarkable things for me was the Umweltfreundlichkeit, which refers to the environmental consciousness or ecology. One example of this could be how much water you use to wash the dishes. I learned a lot on environmental consciousness.

What about the net? How about wasting internet ressources? It is only a question and I assume that the excessive size of that mp3 file was intended. If it can be improved, I think it should be improved.

BTW, the Internet Archive offers unlimited hosting with unlimited bandwith for free and for ever. The requirements are that the materials should be licensed by their copyright owner at least for private copy (otherwise it wouldn’t make sense to offer hosting facilities to anyone). They aim to provide universal access to human knowledge, so reads their motto, and they also accept donations.

Posted in Audio compression. Comments Off on Size does matter

Smaller is beautiful (also when podcasting)

I have just discovered Michael Geist’s lecture Our Own Creative Land: Cultural Monopoly and the Trouble with Copyright has been podcasted (text version also available).

I have an issue with this file. The problem may be only mine (or maybe not). My mp3 player has only 256MB as storage capacity. I know this is not much, but the podcasted file is almost 56MB. IMHO, the file is huge, considering that it contains a lecture (no music in the background or similar).

Analizing the mp3 file, it seems that it has been encoded with stereo and 128 kbps frame rate. Setting encoding parameters to mono and 32kbps frame rate, the resulting file has 14MB. The resulting file is four times smaller, since the compression rate is four times smaller.

Listening to both files on my mp3 player (no iPod), I don’t hear any significant difference between both files. Maybe I should visit the doctor or 32 kbps and mono as settings are enough for an audio file containing only human voice and no music. I know that Michael Geist has nothing to do with mp3 encoding. But it is important for the people at Rabble Podcast Network, because they probably will not have unlimited storage capacity and unlimited bandwith. If their podcasted mp3 files are smaller, it is not only me the one who benefits with more free space and faster downloads, RPN also benefits form less bandwith usage and less hosting space used.

How did I get this? Using lame on GNU/Linux (but there are Windows and MacOS X versions too and they work the same way). This program is a command line application, so you have to type:

lame -m m -b 32 input.mp3 output.mp3

Just in case you wonder, syntax is explained typing lame --help on the command line.

Of course, there are other programs that could generate the same result as the above program. It is only one of them, but with the command line you see exactly what you will get.

Posted in Audio compression. Comments Off on Smaller is beautiful (also when podcasting)

More on interesting fonts

The Greek Font Society has released a new font called Neohellenic. They released improved versions of existing fonts too (available here).

They seem to have fixed the problem with font names, that I pointed to on my last comment (Fontforge complains about font name mismatch, but Mac font names seem to be written using ASCII).

On the new release, I think Neohellenic is an interesting font, but it also has an issue. And I doubt whether it is a bug or a feature. The italic and bold italic faces don’t have the “a” glyph, they use “α” instead. And if this was not accidental, I don’t think is wise for the rest of us (whose mother language is not Greek).

Posted in Fonts. Comments Off on More on interesting fonts

Some interesting fonts

The Greek Font Society has released three fonts with Latin and Greek typefaces (donwload here). The work done shows professional quality and I guess there are more to come (but it is my personal guess).

But for some strange reason, I have problems with Didot (the typeface I like most). The TrueType version has the accented characters messed up. I checked it on W2K, MacOS X and GNU/Linux. And the OpenType version seems to have problems with font names. I have checked it only in GNU/Linux, but Fontforge complains about mismatch in the Windows and Mac font names (for some weird reason, the font names in Mac are written with CJK characters). I did inform the GFS about this and somehow they tried to fix it, but after reporting newer problems, I haven’t received any reply. I’m afraid it only happens to me and the fonts have wrong font names. If anyone could confirm this, it would be very helpful to send a more detailed bug report.

Posted in Fonts. 1 Comment »

First post

As you can read in the time, it is early in the morning and I have just opened an account for a blog, although I already have one (¿Para qué quieres el mundo real si ya tienes internet?). I do like the WordPress interface more than the Blogger one. It has more options and I think I could move my other blog to WordPress.

The title is borrowed from my other blog (after being translated into English) and I will probably change. The subtitle shows what the stuff here will be random thoughts on radom topics. I mean, I try to post here about other topics that aren’t covered in my other blog, which is mainly related to rights in a digital world. (Probably the wise decision to make would be to mix both blogs into one with different tags, but I’m afraid that the hosting service doesn’t support multilingual blogs.)

What are the other topics not covered in the other blog? Mainly my own interests and they are (for sure) diverse. I guess that somehow they’re all technology-related (I mean, they are related to computers and the net).

And why do I write the posts in English being Spanish my mother tongue? This is an interesting question, since I’m not doing it as a way of practising my English. No doubt, my English is far for being perfect. But since English seems to be the lingua franca on internet, I guess it is right to post in English.

Posted in Blog. Comments Off on First post