Alex's Adventures on the Infobahn - linux

Playing Blu-Ray under Linux

2011-04-18T13:43:00+01:00

One of the many deficiencies of Digital Restrictions Management is the fact it makes doing legal authorised things hard for paying customers. For example my brother still can't play Blu-Ray disks on his laptop despite it having the requisite a) drive, b) power and c) display resolution. Because the OS on his machine (Vista?) can't see a verifiable encrypted path to his big screen display it refuses to play his legally purchased disks.

This is one reason why I haven't brought any Blu-Ray disks since the couple I got with my PS3 (to test the Hi-Def goodness). I refuse to buy them while I have no devices under my control* that can play them. Still the conversation with my brother and the fact I had a Blu-Ray drive in my desktop prompted me to see if it was indeed now possible.

My desktop system runs Gentoo which makes running bleeding edge code very easy. I duly enabled the "bluray" and "aacs" use flags and recompiled mplayer. This brought in libbluray and the command line utility aacskeys. Unfortunately mplayer was still unable to play the disk, complaining the disk was still encrypted.

After a bunch of searching the interwebs and drawing blanks on finding any explicit "HOWTO" instructions I resorted to running mplayer through a debugger (one advantage of an Open Source system is there are no "black boxes" to reverse engineer) to see how libbluray was being invoked. It turned out it attempts to dlopen another library libaacs which wasn't on my system. Once I added its ebuild to my overlay I was one step closer.

Unlike the libdecss (which works around the rather anaemic crypto on plain old DVDs) the libaacs library doesn't crack the considerably stronger keys used on BluRay. It relies on a database of Volume keys which can be placed in ~/.config/aacs/KEYDB.CFG which are used to calculate the final decryption keys for the content. Confusingly the format is different from the key databases you may find searching the internet. However the libaacs file format documentation provides instruction on convert the old format into a new format file.

With all of this in-place I was finally able to play my legally owned copy of Black Hawk Down. Yay!

Of course this does require having the appropriate keys for the disc you want to play in your key database. This is where aacskeys comes in. This program allows you to extract the appropriate volume ID key from the disc you want to play. However there are some potential caveats. For starters the program is a little unfriendly to use as it requires certain files to be in the directory your running from. Also some BluRay drive firmwares will refuse to supply the needed keys if the disks are a newer generation than the drive (due to the AACS key revocation model). I'm not sure if a drive will self revoke under Linux if presented with a newer disk but this is the reason there are patched drive firmwares out there.

In the event I was able to verify that aacskeys generates the same volume ID for my copy of Blackhawk Down as was in the KEYDB.CFG database so I know it works for now.

In summary this does show it is possible to play a Blu-Ray disk on a Linux system however there was a fair bit of hoop jumping involved. If I can find a source repository for aacskeys I might start by cleaning it up and making the process of updating the key database a little less painful. I doubt I'll be buying any more Blu-Ray disks until the process of playback is a lot simpler.

* My PS3 is very much Sony's device, a Faustian bargain I accept because I like playing games every now and again. Witness the removal of OtherOS from working systems in the wild by a mandatory firmware update.

Its a kind of Magic

2004-09-29T12:20:00+01:00

I went to New Orleans last year and took a load of photos. unfortunately when I got back I found I could not read my cameras flash card because the crappy FAT filesystem it uses had gotten corrupted. I was very annoyed with this because visiting New Orleans was one of those "once in a lifetime" type things I'd really like to have a record of. One thing I did do however was take a bit-copy of the flash card (i.e. a copy of the device regardless of if the filesystem on it was hosed).

Yesterday in a spare moment I decided to browse Freshmeat to see if there were any FAT recovery tools. I did not hold out much hope as FAT isn't really a native Linux file format and is only really supported so people can duel boot or read floppies. However I did find a tool called Magic Rescue which is a file system agnostic rescue tool that takes advantage of the fact that files have a) magic numbers and b) generally made out of contiguous blocks. The result is I've rescued all the pictures from New Orleans and found my set from the
2003 Sea Elf Special and some pictures from (one of) Anne's graduations. I'll try and get them up on the server by the end of the week.

I spent a most pleasant evening chatting to fellow Six Feet Under fan KMazzy before and after the show. Our general conclusion seemed to be they were teasing us with the promises of hot lesbian action between Claire and Edie that was ultimately unfulfilled (at least on screen). Luckily I can watch the next episode on E4 on Thursday :-)

The Rules according to SCO

2003-11-21T14:00:00+00:00

This anonymous light-hearted moment of unbridled sarcasm is licensed under
Creative Commons. Please feel free to publish this and contribute
additions or corrections.

SCO rules of the game.

Only SCO is allowed to bully and intimidate. No one may bully or intimidate SCO or its partners.
If anyone claims SCO has broken any laws, those laws are automatically one or more of the following: invalid, unenforcible, unconstitutional, violate export laws. If SCO claims IBM, Linux users or anyone else has broken any laws, they are automatically guilty and no evidence is necessary. Only unsubstantiated claims are necessary to prove guilt of others.
SCO is free to change its story as many times and as frequently as it deems necessary. There is no such thing as lying, inconsistency, hypocrisy or self-contradiction.
The most effective legal strategy is to mimic our opponent's every move. Taking the initiative is not necessary.
Hype and sensationalism in the media are all that is necessary to prove that many people owe us money. Waiting quietly for our day in court is not acceptable.
SCO will easily survive for the next 2 years waiting for the IBM and Red Hat trials to begin and then more years for the appeals process. SCO is a highly respected member of the Unix and Linux community and sells many high quality products and services and has a profitable, growing business.
SCO has the moral high ground.
SCO has the silent majority supporting its claims.
SCO executives are entitled to make enough money to own a second house.
Only SCO is allowed to have a "don't ask, don't tell" policy.
Novell, Red Hat, Eric Raymond, Bruce Perens and the entire open source community are illegally conspiring against SCO because IBM is paying them to do it.
SCO is free to use the terms "our valuable IP" and "our valuable intellectual property," even in court, even though they are vage, nebulous terma. SCO does not ever need to specifically state what type of rights, such as copyrights, trade secrets, patents or trademarks.
The claims against Linux are part of a wider debate about intellectual property rights in a digital age. We are not aggrandizing the issues or trying to use smoke and mirrors to prevent you from discovering the emperor has no clothes. SCO and/or its executives are not trying to make themselves look and feel more important than they really are.