[Discuss-gnuradio] Re: digital AM

[Kristoff Bonne]

Greetings,

I'm just new to this mailing-list; but I would like to reply to an earlier
message in this list (I found via web archive).


>> Info about DRM can be found at www.drm.org
> DRM is not a standard -- it's defined by a copyrighted ETSI document
...
Well, ETSI does mean "European Telecom Standardisation institution" so
calling ETSI documents 'not a standard' does sound a bit strange.

The ETSI also is the organisation behind the specs (among others) for
GSM, GPRS, UMTS, DECT, DAB, DVB, MHP, HIPERLAN; and it does
'locatisation' of ITU specs for the EU; so it has quite a 'solid' name in
the world of standardisation ;-)


DRM is now also standardised by the ITU (ITU-R BS.1514); but the problem
with ITU-specs is that they are paying.


> ... that
> can't be redistributed, can't even be viewed without revealing intrusive
> personal information, ...
The only 'personal' information you need to give are your name; your
email-address (which is your account-id) and what country you're from.


> ... and appears to require the use of patented
> algorithms.  Why would anyone use such a restrictive standard when
> freely available, publicly viewable Internet standards are available?
The problem is that all new digital broadcasting technologies are
patented.
IBOC and one of the digital satellite-system in the US (sirius) uses PAC
which also is patented. DRM and the other radio satellite operator (XM)
use "aacPlus" (which is MPEG 4's audio-codec "AAC" plus SBR). Worldspace
uses mpeg 2.5 layer 3 which also is patented.


I think the only one that may be free of patents is mpeg layer II (used in
DAB and DVB) as it may be more then 20 years old (which doesn't compress
that well if you have less then 160 Kbps -for stereo- so is quite useless
here) and the GSM audio codec (which is designed for speech).

The only other option is ogg/vorbis; but this codec does not yet go down
the the low bitrates as needed for digital radio in 9 or 10 Khz bandwidth.


At least, AAC, SBR and mpeg (with the exception of mpeg 2.5 layer III) are
'open' standards (standardised by the ISO); so there is the obligation
that the patentholder MUST grant you a patent on a "fair price". This is
not the case for PAC or mpeg 2.5 layer III.


Anycase, concerning DRM; there is a project at the TU-Darmstadt to design
a 'free' DRM decoder:
http://www.tu-darmstadt.de/fb/et/uet/fguet/mitarbeiter/vf/DRM/DRM.html

There's also a project to design a free AAC 4 encoder:
http://www.audiocoding.com/

But neither have a already released any code.


It would be interesting; once they have released any code; to include it
in GNU radio.

The only DRM 'software' radio is the one from Fhs; and that one is
windows-only.


Cheerio! Kr. Bonne.