Re: embedding messages (ID numbers) in audio
- From: Natalie <natlinnell@xxxxxxxxx>
- Date: Tue, 16 Dec 2008 11:23:58 -0800 (PST)
On Dec 16, 6:09 am, Frnak McKenney
<fr...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hi, Natalie. Sounds like an interesting problem. <grin!>
On Mon, 15 Dec 2008 15:25:20 -0800 (PST), Natalie <natlinn...@xxxxxxxxx> wrote:
Hi everyone,
I want to embed ID numbers in audio so that I can recover them on a
separate device. Some of my constraints:
-The audio will be transmitted from a standard TV/DVD set-up (so DVD
encoding, TV speakers).
-The audio will be received and processed on a cell phone (so cell
phone microphone, processing capabilities (but can be a high-end cell
phone))
-There will be significant background noise picked up by the
microphone
Just to clarify: in your application,
- The original_sound+ID signal will issue from the speakers of an
arbitrary consumer-level "off-the-rack" TV set, stereo, or
similar device, although it might be part of a cable TV channel
airing, radio broadcast, or a CD or DVD.
- It will propagate through normal atmosphere for distances of
(say) 1-20 meters, and is subject to surrounding noise sources
such as conversations from nearby cubicles, A/C, Muzak&friends,
toilets flushing in the next room, and so forth. <grin!>
- It will be heard by anyone in the surrounding area.
- It will be picked up by a cellphone (again, an arbitrary
consumer telephone).
One question: will the ID be processed by a cellphone app, and,
say, display a message on the cellphone screen?
Or will the cellphone be used as a dial-in microphone, that is, will
it send the audio signal to some fixed remote site where your
application will process it?
-The ID numbers will occur about every 30 seconds, and each needs to
be about 10-12 bits of data.
-It would be vastly preferable if the encoding didn't alter the
original audio track significantly; that is, if people listening to
the audio couldn't really tell that there was data embedded in the
audio
For example, if you were designing a system that would (say) allow
an advertising agency representative to walk into a TV store with a
cellphone and find out which of their ads were showing at the
moment. Mixing in (say) high-volume DTMF (touch-tone) digits every
30 seconds would accomplish your _ID_ purpose, but it might be
considered somewhat... distracting. <grin!>
I've looked at the literature on audio watermarking, but this seems to
differ from what I want to do in a couple of significant ways:
-I'm not worried about a malicious attacker, so detection and spoofing
aren't concerns
-I'm broadcasting over a very noisy channel
I'd appreciate any info that people could point me toward -
applications, literature, websites, whatever.
I don't know if it will work over a cellphone link, and the data
rate may not meet your specifications, but the NIST WWV time
broadcasts contain digital data mixed in with audio by using a 100Hz
subcarrier. You can obtain a description of the format used from
NIST Special Publication 250-67 "NIST Time and Frequency Radio
Stations" by searching for "250-67" at:
National Institute of Standards and Technology
http://www.nist.gov/
Whatever method you finally choose, given the possible variations in
ambient noise I think you ought to assume that the delived signal
would be extremely error-prone (in multiple ways), and
intermittently delivered (cell signal loss, PA loudspeaker, etc.)
and plan accordingly.
I'd also advise that, after you have a final approach and have
tested the error rate, that you make your (proposed?) customer
aware of the system's limitations ("I know you'd prefer
up-to-the-second reports, but cell towers _have_ been known to fail
occasionally..."). Your goal in doing this would not be to "talk
down" your work <grin!> but to explain the constraints it has to
live with -- mostly not of your making. Customers don't generally
like surprises.
Hope this helps. At the very least, your correcting any of my
mistaken assumptions will help clarify the situation to the other
readers.
Frank Mckenney
--
Over the ages, the condition of the arts has been seen as a part
-- a striking and important part -- of the exercise of critical
imagination, of the human mind, in their broader compass.
-- Robert Conquest, "The Dragons of Expectation"
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)
Ah! So sorry not to be completely clear. You were correct on all
your clarifying points. As to your question: I'd like to do the
processing _on_ the cellphone. Thanks for the pointers, I'm reading
through the docs. This isn't my specialty, so it's kinda slow
going. :)
.
- Follow-Ups:
- Re: embedding messages (ID numbers) in audio
- From: Frnak McKenney
- Re: embedding messages (ID numbers) in audio
- From: makolber
- Re: embedding messages (ID numbers) in audio
- References:
- embedding messages (ID numbers) in audio
- From: Natalie
- Re: embedding messages (ID numbers) in audio
- From: Frnak McKenney
- embedding messages (ID numbers) in audio
- Prev by Date: Converting Stereo to Mono taking into account Phase modulation
- Next by Date: Re: Converting Stereo to Mono taking into account Phase modulation
- Previous by thread: Re: embedding messages (ID numbers) in audio
- Next by thread: Re: embedding messages (ID numbers) in audio
- Index(es):
Relevant Pages
|
