Mylatest blog entry began with this paragraph:
Messing with MP3 files is, for some people, a synonym for illegal use of copyrighted music. Well, actually it's not.
The reason I wrote that incipit remained unclear to many, that didn't seeany link between this first phrase and the rest of the article. I therefore decided towrite a few blog entries on the subject. This time I'll talk about theMP3 format in itself.
MP3 is a popular lossy audio compression format. In some ways, MP3 is for audiofiles what JPEG is for still images. JPEG, as you may know, is a lossyimage compression format; it's effectiveness builds on the fact that JPEGremoves information that the human eye cares less for. Similarly, MP3s removeinformation that are less audible to human hears.
A JPEG compressed image is different from the original one, and differencesare quickly spotted by a watchful eye; similarly, if you listen carefullyto an MP3 file you can feel that there are sounds somewhat degraded.
MP3 as a format owes its success to a couple of factors. The first is a very goodcompression/quality ratio; the second is our old beloved Napster, whichin 2000 made itvery easy to search for and exchange MP3 audio files;it also made peer-to-peer programs so popular that someone thought wewere at the beginning of a new frontier in internet services, despite the fact thatthe P2P paradigm in itself was quite old instead (think about theold talk UNIX utility to get an idea).
But success came at a cost: a lot of the files shared with Napster wereillegally shared copyrighted music. So, for some, MP3 became synonymous with "illegal audio files". My latest blog entry came from here: having anMP3 file doesn't mean that you have something illegal in your hands.
I could stop here telling the story of MP3, but since this isFree Software Magazine there something more that's worth saying.To cut a long story short, MP3 is not a free format, despite its widespreaduse and its being a de facto standard.Thomson holds the patents on theformat and it's actively trying to enforce those patents all over theworld.
But wait, there is more. TheFraunhofer Institutewas involved in the creation of the format since the beginning, andcreated the first MP3 encoder. Well, it holds a license that allows itto require a licensing fee for all programs that use the MP3 format(both encoders and decoders); Thomson manages all the licensingprocedures on their behalf. For more information you can have a lookat Fraunhofer'sFAQ onMP3 and at themp3licensing.com web site.
All these licensing and patent issues made the free software communitydevelop a new audio file format that's now known asOgg Vorbis. Let's cut a longstory short again, and say that Ogg is sort of a multimedia containerfile format, that is a specification for files that may contain audio and/orvideo tracks. Vorbis, in turn, it's an audio encodingformat. As you may now have guessed, Ogg Vorbis files are Vorbis audiostreams contained in Ogg containers. Ogg Vorbis combines both the advantagesof MP3 (a high compression ratio and high quality for audio files) andbeing a patent-free, open file format, something that FSM readers mayappreciate. It hasn't the same popularity of MP3, nevertheless it's supportedby many media players, both free (like XMMS) and non free (like WinAMP).It's also supported by a number ofportable audioplayers.
And that's all for this post. Next time I'll talk about legal issuesconnected to the use of MP3 files, and in particular about thelegal issues related tomyprevious post. I'll be helped in this effort byMassimo Farina, an Italianlawyer and a dear friend of mine, who's specializing in legal issuesrelated to new technologies. Until then, enjoy FSM!
Comments
Ogg versus MP3
The biggest problem with Ogg format is that not many portable/embedded players support it. This means that if you store your compressed audio in Ogg format, and you want to listen to it on cheap embedded players, you will have to transcode the data to MP3 anyway.
Which is a pain. So many people choose to just keep their music in MP3 format.
This isn't much of an issue for me, because I just don't have any embedded compressed-music players! But every time I think about buying one, I agonize over the process of finding a good one that supports Ogg (not much luck at the Walmart -- I'd have to buy something online, probably).
Obviously, one reason for MP3's success over Ogg is that it's been around longer. But of course, WMA is newer than either, and many new players support it, but not Ogg. One might suspect a conspiracy!
However, I have learned that at least part of the problem is (or at least was) technical: Ogg apparently uses a floating-point based algorithm to do its compression, whereas both MP3 and WMA use integer-based math. This has a significant impact on the CPU requirements for hardware that processes them. The Ogg format was designed, I believe, with Intel-based PCs in mind, as the most efficient way to use that hardware for compression (and many people seem to think that Ogg files produce better fidelity/compression performance than MP3), but they didn't really accomodate the needs of embedded devices.
Thus many devices just don't have the CPU cycles needed to process Ogg.
IIRC, however, there were some improvements in this direction (an integer-based algorithm for Ogg files), but I haven't kept up with that.
Vorbis and foating point
Vorbis does indeed use a floating point encoding process - and so do WMA and MPEG-1 Layer 3 (mp3). Encoding the files is one thing; decoding them is another, and you can actually decompress MP3 files with integer based processes. But so can you Vorbis! The 16-bit integer based decoder is free and is called Tremor. In matters of CPU cycles, Vorbis demand isn't as high as you'd think. Hovever, and contrary to mp3, it requires a few more kilobytes of fast RAM (32kb if I'm not mistaken) for the actual decompression - something which can actually be hard to allocate on embedded devices (mp3 requires 4kb if I'm not mistaken).
mp3 starts with cutting off the higher frequency range and muffles the sound the higher the compression ratio is; it is bitrate-based, although an abuse of its format definition allows it to work in a quality based (variable bitrate) compression scheme (see LAME). It includes several filter passes so as to remain audible (though eventually muffled) in high compression.
WMA 'simplifies' the sound wave 'appearance' until it reaches the required bitrate. It is extremely fast due to almost no filters being applied - which provokes ringing, metallic noises and general nasty harmonics to be generated in, say, 64k/sec compression (while an MP3 compressed at this rate will be automatically downsampled to 22 kHz and muffled, but much easier on the ear)
Vorbis won't reach 64 k/sec if you require quality to remain high (it is a variable bitrate encodig process) but on comparable sound quality it'll beat WMA by 10-15% and variable bitrate MP3 by 20%. It won't encode non stereo, lower-than-CD quality efficiently though.
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A computer is like air conditioning: it becomes useless when you open windows.
Wow, thanks
Wow. Thanks for coming up with the facts on Ogg/WMA/MP3. I feel greatly enlightened! :-)
Pirates! *harr, harr*
I'm looking forward to your next blog post! Maybe you'll also want to write something about so called 'piracy', legal issues and what 'intelectual property' does to creative works.
Please have a look at the political Pirate Party which formed in Sweden around the worlds largest BitTorrent Tracker The Pirate Bay and the anti-copyright organisation Piratbyran.
This is a movement which aims to reform todays restrictive copyright system with ideas of for example Lawrence Lessigs Free Culture in mind. A lot of the ideas of the Free Culture Movement are actually derived from the ideals of the free software movement.
Ogg and FLAC
Well, I guess the very nature of Ogg, i.e. open, is the hindrance to adoption. Since it is open, I dread to see a DRM slapped on it so that recording companies can make sure that their music is difficult to pirate. The reason why AAC with Apple's Fairplay and WMV of Microsoft with their own DRM are gaining advantage over open formats.
Another file format that I have encountered is FLAC, which uses lossless compression. Although I have yet to see a device supporting it, it may also be a good alternative to other proprietary file formats.
As it stands...
...there are players that support Vorbis and/or FLAC. The problem with the latter is the much longer encoding process required, and the lower compression ratio (highest compression will yeld a file that is around 60-80% smaller than uncompressed, while Vorbis will result in 90% smaller files that still sound extremely good in a fraction of the time).
FLAC is an excellent compressor for sound archival, Vorbis is much better at consumer playback.
DRM isn't really a concern, as a matter of fact: MP3 doesn't support it, and no players these days can do without MP3 playback; Vorbis is a MP3 replacement that happens to have much better quality than WMA or AAC, but which is not commercially enforced. It all comes down to marketing.
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A computer is like air conditioning: it becomes useless when you open windows.