MP4 was developed by a Web content company called Global Music Outlet (GMO) and based on AT&T's a2b audio compression format. A2b will be part of MPEG-4, so GMO is essentially appropriating the informally used name for a proprietary subset of the industry standard. RIAA has even established a Secure Digital Music Initiative (SDMI) to develop a copyright-protected alternative to MP3. GMO says MP4 is a "midstep" between MP3 and the SDMI, although pr ecisely what that means is unclear. Like MP3s, MP4s will be freely downloadable, but a2b contains copyright protections MP3 does not have. Presumably these will also be included in MP4. MP3, which many consider a de facto standard given its widespread use, and now MP4 compete with secure download formats such as a2b, the product of AT&T Labs' music delivery technology arm a2b Music, and technology from Liquid Audio. GMO used encoding technologies licensed from AT&T Labs for copyright protection in its MP4 format. Despite the play on the MP3 name, MP4 technology is different. For one thing, MP4 is an executable file, meaning that an embedded audio player is launched when the MP4 file is opened. In contrast, MP3 files use software called WinAMP to play, and MP3 audio files can be combined with other MP3 files to create a customized play list. http://www.5ddesign.com/html/audioS2.html AAC AAC, or "MPEG-2 Advanced Audio Coding", is originally known as "MPEG-2 NBC" - Non Backwards Compatible). It offers a better compression ratio than MP3. Formal tests have demonstrated that it is able to provide better audio quality at 96 kbps than MP3 at 128 kbps. AAC was declared international standard by MPEG by the end of April 1997. The same Fraunhofer Institute this time cooperated with AT&T, Lucent Technologies, Sony and Dolby Labs to develop it. Promoted as the Audio Data Compression for the 21st Century, it has become the native base for many latest and most sophisticated audio codecs, including a2b, Liquid Audio, and it will be used for upcoming MP4 format (together with VQF). AAC is being licensed by Dolby Laboratories. There are several derivative forms of AAC codec today - including a2b, LQT, ISO AAC and Astrid/Quartex ACC versions. We recommend downloading the Liquid player and listening to the samples encoded with the best of the AAC family codecs - AAC LQT (see the LQT section below). a2b The a2b codec, a AT&T proprietary audio compression algorithm, is based on AAC and is fully called the "MPEG-2 AAC Low Complexity Profile Audio Coding ". It delivers higher fidelity than MP3 at faster data rates with a compression factor of up to 20:1. It uses encryption that limits playback to one player and restricts the number of plays. With a2b the very first commercial application of AAC was started by AT&T. a2b player was the first one displaying cover art, lyrics and credits. No coding software is publicly available for this format - so we can not make our own sample of a2b on this 5dDesign Audio page. However, you can download free a2b player and check some free music tracks from AT&T's Downloadable Music Service ( http://www.a2bmusic.com/). MP4 MP4 is probably the most confusing audio codec term discussed here: * it is often wrongly used to mean MS Audio Codec 4.0; * the intentional promotional use of the term MP4 to cash on MP3 * popularity has added confusion to this name. Neither "MP4.com" * nor "chaosmusic.com" have any relation to MP4. Companies like * "ChaosMusic" and "eMotive.com" call the product "MP4", but it * is really an executable player embedded into every AAC file * (hardly a great idea in the age of widespread fear of computer * viruses). It is interesting that the very same feature is * available in the a2b player, while "eMotive" has close * relations to AT&T, so it may well be that this confusing "MP4" * format is a courtesy of AT&T; * sometimes when using this term, people mean MPEG-4 SA * (Structured Audio) which is not a compression codec, but * rather a new audio synthesis algorithm coming to replace MIDI. MPEG-4 is a standard currently under development for the delivery of interactive multimedia across networks. The correct use of the term MP4 should refer to MPEG-4 GA (General Audio) often described as an ACC and VQF merger. It is expected that MP4 at 96 kbps (stereo) will give about the same quality as MP3 at 192 kbps (stereo) - thus producing half sized files for the same quality. There will be no "layers" in MP4. So all assumptions like "MP4 is MPEG-1 Audio Layer 4" or "at the moment it is MPEG-4 Audio Layer 1 and the final standard will be MPEG-4 Audio Layer 3" are nothing but an educated guess. As yet, no players and encoders are available for this format (at least no fully functional ones; so called "MP4 AAC" encoders are actually doing the same that ISO AAC coding does - slow encoding and very high CPU power utilization for decoding). Back to Contents http://www.macnn.com/news/22219&startNumber=27 Norwegian programmer cracks Apple DRM The Norwegian programmer who distributed the first widely used tool for cracking the copy protection technology found on DVDs has turned his attention to Apple's iTunes. Late last week, programmer Jon Johansen posted a small program called QTFairUse, which evades the anticopying technology wrapped around the songs sold by Apple in its iTunes store. Johansen's program, which works only for the Windows version of iTunes, is the most recent move in the ongoing struggle digital rights management technology creators and hackers. http://www.macrumors.com/pages/2003/11/20031122001549.shtml QTFairUse - iTunes Digital Restrictions Management (DRM) Circumvented? Approved/Edited by arn on Saturday November 22, 2003 12:15 AM from the rumors dept. A Register.co.uk article reports that the author of DeCSS has written a small command line Windows utility (QTFairUse) which "will dump the output of a QuickTime stream to a file". The Quicktime stream in question are AAC files. While TheRegister tries to explain away the hack as an implementation of an analog stream-ripper, it appears to be a bit more sophisticated than that... According to the QTFairUse README: Usage: Open and play a MPEG4 AAC file in QuickTime Player. The raw AAC data will be written to Desktop/QTFairUse.aac The application clearly piggybacks off of Apple's Quicktime player and patches the "quicktimempeg4.qtx" file of Windows' Quicktime. It then outputs this "raw AAC data" to a file while the original AAC file plays under Quicktime. The proposed theory is that the application intercepts the Decrypted AAC data from Quicktime after authorization has taken place, and saves out the resultant decrypted (de-DRM'd) AAC data. Based on limited testing from one user with Quicktime 6.4 under Windows... the application does create DRM-free ".aac" files when Protected AAC files are played through Quicktime. These output files, however, are unplayable in their raw form in most players. The reason for this is that these files represents the true "raw" AAC data that has been passed through to Quicktime to play. All header information has been removed. To create playable files, a further packaging of the files is required to add the appropriate MPEG headers. But the application does work as suggested -- stripping DRM (RM adds: digital restrictions management) from your protected AAC files (though is not of any practical use in its current form). In any case, this is the first public attempt at breaking Apple's Digital Rights Management format. The potential for abuse and concern for an application such as this is greater than simple "stream rippers" in that this would introduce lossless ("perfect") copies of protected files. http://www.scifihifi.com/weblog/mac/AppleDRMRevisited.html Apple DRM Revisited Posted: 20:54 | Category: [/mac] | Permanent Link: # In a previous post detailing my research into the iTunes Music Stores digital rights management scheme, I promised to continue hacking away at the problem and post updates on my progress. In keeping with that promise, here is an account of my recent hacktivities. The first thing I should mention is that Phil Schillermania Schiller recently gave an interview to BusinessWeek wherein he, for the first time, publicly names the ITMSs DRM scheme. It turns out that Apple is using a system called FairPlay, which was evidently developed by a company called VeriDisc. Schiller, in keeping with Apples silence on DRM matters so far, is extremely cagey about discussing the true nature of the protection. When asked Is there any DRM built into the downloads themselves or is it all in iTunes 4, Schiller responds: No, its all built into the [iTunes] system. Our goal is to make it transparent for the user so that they never have to think about DRM. Were using a DRM technology under the hood called FairPlay. Its a DRM technology used by iTunes and QuickTime at the system level. To which I respond: lies! This is obviously falseif the downloaded files didnt contain any DRM information you would be able to copy the same file from computer to computer and iTunes would be none the wiser. Readers who saw my earlier post may remember that I closed with a bit of speculation as to which part of the AAC file actually contains this DRM information: the drms atom. The atom name itself strongly suggests this, and a quick comparison of the relative structure of protected and unprotected AAC files seems to reinforce the idea (note that the only obvious difference between the two is that the protected file contains a drms atom in place of the unprotected files mp4a). This, then, brings to mind an obvious question: would removing the drms atom and replacing it with an mp4a atom effectively remove the DRM protection? To find out, I began reworking my original AAC parsing code so that it could read an entire atom structure into an object hierarchy, modify it, and then write the whole thing back out to disk. It took awhile to get my code to the point where it could produce files that didnt crash QuickTime, so you can imagine my elation when I finally managed to generate a valid, unprotected AAC file (as confirmed by QuickTimes movie info window). [picture] The original, protected AAC [picture] An AAC output by my code Unfortunately, my elation evaporated as soon as I actually tried to play the file, only to encounter silence. That is, QuickTime had the length and all of the file properties (sample rate and so forth) correct, and would begin playing the file normallyit just wouldnt produce any audio. Further research suggested that I probably needed to preserve the elementary stream descriptor atom, which always seems to be embedded within the drms or mp4a atom. With this in mind, I rewrote my code so that it preserves the files esds atom within the substituted mp4a. Unfortunately, the results are the samesilence. So, I seem to have reached an impasse. I have produced some pretty nice code for parsing QuickTime-like files, but I really need to take a break from my hacking efforts to get some much needed rest and work on other projects, so Ive decided to publish my latest code and shelf the project (at least for now). It can be downloaded (as usual) as a Project Builder project: - AACExperiments2.dmg Once again, I ask anyone who makes progress based on this code to keep me informed. I would be particularly interested to hear from someone who might be able to bring a better understanding of MPEG-4 to bear on the problem (this project has definitely put learn more about MPEG on my To Do list!). http://www.ipodlounge.com/forums/archive/topic/17022-1.html Jon Johansen, the Norwegian programmer who created DeCSS, the first widely used tool for decrypting the copy protection in commercial DVD movies, announced a similar hack this week for the Digital Rights Management (DRM) (RM adds: should be corrected to the non-polemical "digital restrictions management") technology that protects (RM: controls and obscures, not "protects") songs purchased from Apple Computer's iTunes Music Store. The hack, which Johansen calls QTFairUse, casts doubts on Apple's ability to protect the intellectual property rights of artists who sell music on iTunes Music Store and comes just a month after the company opened the service to Windows users. Johansen posted QTFairUse to his "So sue me" Web site this past weekend. QTFairUse is a small command-line utility for Windows that shows developers how to bypass the security features in Apple's protected Advanced Audio Coding (AAC) format, which the iTunes Music Store uses. The utility doesn't create a workable, playable, protection-free music file, but its source code will help other hackers bypass Apple's DRM security in their own applications, eventually leading to a complete breakdown of Apple's licensed DRM system, FairPlay. Critics have long alleged that in the past much of Apple's software-development advantage came from its small, tightly controlled market. Now that Apple is pushing DRM-enabled products such as the iTunes Music Store and the iPod into the wider Windows world, the company is finding out how difficult it is to control the teeming masses. This week's iTunes Music Store hack is actually the second time programmers have hacked the service in the past month and the third time this year. A tool called MyTunes, released last week, lets Windows users steal music that other Windows and Macintosh iTunes application users share for streaming, although it doesn't decode songs purchased from the iTunes Music Store; Apple patched a similar problem in its Mac version of the iTunes application earlier this spring. Apple's primary competitor, Microsoft, created its own DRM scheme for its popular Windows Media Audio (WMA) and Windows Media Video (WMV) formats but built renewing capabilities into the technology, which helps Microsoft survive security exploits. Whether Apple's FairPlay technology supports this renewing functionality is unclear at this point, and Apple has been characteristically quiet about its DRM use, preferring instead to foster the impression that the company is more customer-centric than Microsoft and less beholden to content creators. But the reality of the situation is that Apple has worked hard to strike deals with the recording industry and did a fantastic job of jump-starting the concept of inexpensive, downloadable, legitimate music. Let's hope that this DRM breach won't cause record companies to reverse their decisions to work with online music services. http://www.the-gadgeteer.com/itunes-review.html They do however put a few restriction on the music that can be bypassed if you think about it (*cough* re-rip) You can only record 10 sessions at a time from a set playlist, but you can move one song, and now you have 10 more burns. You cannot record the AAC/MP4 (iTunes store bought music) as files to a disc like you can mp3s, you can only record them as audio discs. (*cough* re-rip) But this is all small potatoes DRM stuff. Your original AAC/MP4's can only be on three authorized computers at a time. (Do I hear someone coughing?) Again - *very* minor inconveniences, but not enough to take away from the simple pleasure of using this product. AAC seems to be a nice format. Truthfully - I cannot hear any difference between AAC, MP3 or a regular CD. (of course - I've been to one too many concerts over my lifetime too!) [...] As a music store, there are minor DRM issues with iTunes. (NOTHING like it's competitors draconian DRM practices though.) If you don't have an iPod, you won't be able to export your store purchased music to your mp3 player unless you burn an audio disc and then re-rip it to mp3. AAC files purchased from the store are not exportable, but can be burned to as many audio discs as you want, only having to change their play order every 10 burns. The iPod does not have these limitations and can easily store and play any and all songs you can put into the library. AAC files you burn yourself can be exported and playlists burned as many times as you want. http://joi.ito.com/archives/2003/04/29/the_sucking_sound_of_drm_itunes_4.html The sucking sound of DRM - iTunes 4 07:13 JST » Intellectual Property - Music I just downloaded iTunes 4, set up my .mac account for the music shop and started browsing around the music shop. Ooo, I don't have that Orb CD, "click", I wonder if they have.... "click"... "downloading..." "hey..." "click". Now maybe I'm not a good sample, but iTunes 4 is to music downloads what iPod was to mp3 players. Of course you have to download iPod patch to play the AAC protected music format and you are not downloading sharable mp3's. My little foray into the DRM'ed music space is really an experiment on myself to see if a proprietary system can make the experience compelling enough to make people say, "screw it, I'm going to use DRM." So far, the experience for me is that actually quickly finding clean copies of music I'm looking for and having it seamlessly arrive in my iPod is worth the $.99/song they are charging and the fact that it's protected. THAT'S SCARY. It's the sucking sound of Hollywood you're hearing here... hmm... Anyway, I'm going to play around with it a bit more before I decide for sure whether this is a killer service, but I just thought I'd post this urgent news so you could try it for yourself. ;-p Update: Not nearly as many songs that I want as I initially imagined. They're like trying to get my to buy the Village People and stuff... Search seems broken -- it gives me errors. Keeps trying to tell me I can't use the service because I'm in Japan -- I keep trying to trick it into thinking I'm in the US. a good roundup on Marc Canter's site. Update 2: BAAAAD news. So I bought a bunch of albums and songs and was happily downloading them thinking about how much money I had just spent. Then. "There was a problem with Music Store. Please try again later." I still have the songs I've downloaded and they are there, but all of the stuff that was in the queue to be downloaded. Gone. "click" "You already have a copy of this dumbass, do you want to buy it again?"... fill out bug report asking whether I can reinstate the downloads or check whether I've been billed. "thank you for your bug report. We can will not respond to this request directly, but we appreciate your dumbass suggestions..." shit... Anyway, I will make sure I check my credit card bill next month. Until then, I will buy...download...buy... and not queue up downloads. Update 3: When I restarted iTunes it started download all of the music I bought. phew... all about apple drm: http://mac.against.org/space/AAC http://the.taoofmac.com/space/AAC AAC Also known as Advanced Audio Coding, AAC is the MPEG-4 audio standard that supports, amongst other things, multi-channel audio (as in more than two). * Official Site DRM Restrictions Note: More info here, with mentions of Fairplay. (As reported in MacRumors for the Apple implementation - should be mostly the same for other AAC-related DRM policies): How it Works Surprisingly few details about the implementation of the AAC DRM have been revealed. The following represents a list of restrictions and capabilities for consumers as gathered at this time: * Protected AAC files have the extension: .m4p -- ripped AAC files are .m4a * Unlimited CD Burning of Protected AACs * Only the iPod and Apple's iTunes, and it seems Quicktime?-based apps currently allow playing of these Protected AAC's. * Up to three computers (at one time) can be authorized to play Puchased AAC's. Deauthorizing your computer and reauthorzing new computers is relatively simple (Note: uses the iTunes "Authorize/Deauthorize Computer" menu, no details as to the transport mechanism and PKI? employed) * Playlists containing any Protected AAC's can only be burned 10 times. You must change the list manually before you can burn again. Tech Note * Burning a Protected AAC to a CD strips all encoding and DRM. That CD can then be used as any CD song is used. The quality of the song on the CD is identical to the AAC version. However, then ripping the song into MP3 or AAC will result in loss of some quality. While ripping a song into any lossy compression format will result in loss of quality -- recompressing these previously compressed songs may exaggerate the quality loss. Your results will vary depending on the exact piece of audio. Anecdotal evidence suggests re-ripping into AAC yields better quality than re-ripping into MP3. * Transcoding from Protected AAC to MP3/AIFF? from iTunes is prohibited by iTunes. * If you're listening to a shared library or playlist, iTunes skips any purchased music in the list (if the computer is not authorized to play the music). To listen to a purchased song in a shared library or playlist, you need to double-click the song. If your computer is not authorized to play songs purchased by the person who is sharing the song, you'll need to enter that person's Apple Account ID and password to hear the song. Tech Note * According to Apple: iTunes will only play AAC files that are created by iTunes or downloaded from the Music Store. "Other AAC files that you find on the Internet or elsewhere will not play in iTunes." However, Anecdotal evidence does not support this. Users have reported being able to play AAC files encoded outside of iTunes. Tech Note * AACs you rip from CD yourself (via iTunes) have no restrictions. * Authorization/Deauthorization appears to be based on a central server model... as Apple claims that "Initializing the drive will not deauthorize the computer. If you will be initializing the drive, deauthorize the computer first, then initialize the drive." Tech Note