linuxmafia.com 2016/linuxmafia.com.tar/linuxmafia.com/kb/Apps/AV/mp4

Text File | 2006-01-17 | 22KB | 486 lines

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).

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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