Articles from May 2010

I never thought I'd ever own an Apple computer. Now I do, but still the Apple OS doesn't really cut it for what I have to do for work. Hence, shortly after it's arrival, I went looking for some chicken blood, scented candles and a mysterious black robe: ready to perform the iHeresy and install Windows 7 on the brand new MacBook Pro!

Thanks to Apple, the heretical procedure is quite easy: the Snow Leopard installation disc you get with your Mac contains all Windows drivers you'll need and Mac OSX itself can do the partitioning work for you and setup the EFI bootloader correctly. In most cases the official installation guide will be perfectly fine to install Windows on a Mac PC.

However, if you'd like to setup a triple boot with Mac OSX, Windows and Linux, you'll need a more advanced solution: rEFIt, a toolkit that lets you customize the bootloader and boot from almost everything. Just download the latest package and install it in Mac OSX (it's a simple .dmg package). Refit won't show up as an installed application, but at the next reboot it should already show up instead of the gray Apple logo.

Now you're ready to partition your Apple's hard disk and install any other operating system. To do so, I suggest this great guide (which is slightly outdated, but nonetheless valid and very detailed). Essentially you'll have to follow this three steps...

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I've been working at the University of Urbino for a couple of months, trying to get a working example of a Web TV over a wireless multicast transmission channel. All of the team's efforts (me and a couple of other people) are focused on the public event of tomorrow:

We will try to demo a proxy server (which has been built primarily by myself using ASP.NET and GStreamer) that receives various Web TVs from the Internet (our partners for the event are StreamIt and the italian RAI) and 1080p high definition movies stored locally on the server, transcodes the A/V stream and forwards it via multicast.

The multicast stream will then cross a radio link (provided by our partners at Essentia) and get to 10 client PCs, representing 10 households that might wish to receive TV contents through their wireless connection.

Essentially the demo will try to prove that such transmission methods provide much lower impact on the available bandwidth (which can be very scarce on metropolitan wireless connections, especially if shared between many clients of the same household). Wireless multicast TV is usually limited to “traditional” media delivery similar to that of the standard TV broadcast (that is, no on-demand video), but could be integrated with some innovative commercial solutions (for instance, on-demand video that gets cheaper as more users decide to watch it).

If everything works as planned (and so far it didn't ), starting tomorrow I'll have more time to write about the things we worked on: lots of stuff, starting with the RTMP protocol, GStreamer, RTP multicast streaming...

The Wireless Multicast TV event has been a success, everything worked correctly (even exceeding our initial expectations in fact). We used the following setup during the presentation:

Our objective was to get real time Web TV contents from the Internet and stream them locally to a certain number of clients using multicast over a wireless network. The incoming media resources from the Internet were handled by our proxy server (the box I worked on prevalently), re-encoded and then streamed to multicast addresses. The inner network was a wireless link, composed by one antenna linked to 10 CPEs. Each CPE was then cabled to a client computer, playing back the video streams.

The main point of the experiment being that, since multicast can be very cheap if implemented on a wireless network, it can be successfully used to deliver real time media without incurring in the typical bandwidth saturation that would be caused by using unicast streaming.

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A minor update to OnTopReplica is available since a couple of days via the ClickOnce installer or on the CodePlex repository.

This new version adds some minor tweaks (alphabetic region ordering, some minor redrawing issues, etc.) and adds a new Czech translation to the ones available (italian and english at the time). Many thanks to René Mihula for the translation!

In the meantime, a portoguese translation is in the works and for the upcoming 3.0 version I'm planning to integrate some Windows 7 specific features (Vista will still be supported of course).

Windows Vista introduced a very nice feature called “hybrid sleep” that simplifies power management and allows the PC to enter a deep sleep state (S2 or S3) while persisting the RAM contents to disk. In this case, even if the computer lost power it could always resume its state without data loss.

I like this feature quite much and it appears to have become the default “sleep” state on most operating systems (Mac OS X had it for some time and the latest Ubuntu appears to use Hybrid Sleep as well by default). In some cases however you'd perhaps want the PC to hibernate and skip the sleep state altogether (i.e. enter the S4 state directly). Unfortunately Windows hides the hibernate option: your only option is to enter sleep, wait until the RAM state has been written to disk and then power off the computer manually.

Needless to say, this is ugly and could lead you to powering off the PC before it had a chance to write all data to disk. In order to force Windows to enter hibernation directly (without having to disable Hybrid Sleep), you'll need to run the following command from the command line (no need to run as administrator):

%windir%\system32\rundll32.exe PowrProf.dll, SetSuspendState 0,1,0

This will quickly fade out the screen, save the RAM to disk and power off the computer as if you clicked on the old “hibernate” option.