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A Proposal for a Copy Optimized DVD Audio Format

 
 
Imhotep
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      09-07-2005
"I'm writing to suggest the community work together to specify a standard
for the format of DVD Audio discs that will be Free as in Freedom. There
are a couple of competing standards proposals for DVD Audio discs that have
the advantage of higher audio fidelity than Compact Discs (sampled at, say,
24 bits instead of 16) and that can hold more minutes of music, but it's
quite clear that the companies behind the standardization efforts consider
copy-protection their first priority."

http://www.kuro5hin.org/story/2005/9/1/25644/72726

Imhotep

 
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Unruh
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      09-07-2005
Imhotep <(E-Mail Removed)> writes:

>"I'm writing to suggest the community work together to specify a standard
>for the format of DVD Audio discs that will be Free as in Freedom. There
>are a couple of competing standards proposals for DVD Audio discs that have
>the advantage of higher audio fidelity than Compact Discs (sampled at, say,
>24 bits instead of 16) and that can hold more minutes of music, but it's


Well, just because you sample at 24 bits does not mean anything. 16 bits is
a 95dB floor, at which point electronics noise becomes a real problem. Ie,
the chances of actually getting anything for the extra 8 bits is low.
Now, sampling at a higher rate (88200 say) could well be worthwhile,
especially in getting rid of aliasing of the signal due to high freq noise.
(22K shannon freq is a bit too close to the auditory threshold.


>quite clear that the companies behind the standardization efforts consider
>copy-protection their first priority."


Yes, I suspect that is true. They have been burned, but they have a really
really hard row, since those digital signals have to be delivered to
something-- speakers, amplifiers, etc. sometime.

Of course they could just make the audio output so crappy, but then why any
improvement in the digital signal.




>http://www.kuro5hin.org/story/2005/9/1/25644/72726


>Imhotep


 
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Jim Watt
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      09-08-2005
On 7 Sep 2005 18:24:32 GMT, Unruh <(E-Mail Removed)> wrote:

>22K shannon freq is a bit too close to the auditory threshold.


have you ever tested the highest frequency you can actually hear ?



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Jim Watt
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Steve Welsh
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      09-08-2005
>>22K shannon freq is a bit too close to the auditory threshold.

I agree, 30 or 40K would work a lot better.

> have you ever tested the highest frequency you can actually hear ?
> Jim Watt


Not that simple, Jim. That works fine for pure sine wave tones, but
unfortunately the human ear plays silly tricks on us. That's why lots of
church organs have 'acoustic' pipes, or quints. It works by making the
brain think that it is hearing a tone that actually isn't there. It's
part of what makes MP3s work.

The same thing applies at the high frequencies. The 'difference tones'
of high overtones of most musical instruments are what give them their
particular 'timbre'. Unfortunately, cutting off the frequencies of
recordings at 22KHz robs us of the chance for our ears to do their work.
That's why you can never quite get that 'live music' experience from
standard CD PCM.

Totally off the security topic, sorry.

Cheers,
Steve
 
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Jim Watt
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      09-09-2005
On Fri, 09 Sep 2005 00:15:01 +0100, Steve Welsh <(E-Mail Removed)>
wrote:

>Totally off the security topic, sorry.


It is, but I have an interest in audio engineering. The highest
tone I ever heard was 17khz some years ago. As discussions
about audio perception are subjective its perhaps best left
alone, although most live music now sounds better as the
speakers amplifiers and equipment used has improved

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Jim Watt
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Unruh
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      09-09-2005
Jim Watt <(E-Mail Removed)_way> writes:

>On Fri, 09 Sep 2005 00:15:01 +0100, Steve Welsh <(E-Mail Removed)>
>wrote:


>>Totally off the security topic, sorry.


>It is, but I have an interest in audio engineering. The highest
>tone I ever heard was 17khz some years ago. As discussions
>about audio perception are subjective its perhaps best left
>alone, although most live music now sounds better as the
>speakers amplifiers and equipment used has improved


Yes, they have. The problem with a low cutoff is that of aliasing. Ie,
noise etc at a frequency of 28KHz is aliased down to 14KHz by the sampling.
Also, since you want to get rid of that high freq stuff so that you do not
get aliasing, you need to put in filters. No filters have a sharp cutoff.
Thus the filters have to start cutting in at 5 or 10KHz to drive
the stuff about 22 KHz to a low enough level.

Ie, the 22KHz is a bit too low.
Note that children can hear up to about 25KHz. The reason women and kids
find TVs so annoying is that most are designed by male engineers who are
completely deaf above about 10KHz, and cannot hear the flyback transformer,
which on much consumer junk shrieks loudly. Were it 60Hz humm the sets
would never never have been designed that way, but at 15-17KHz, its "What
humm?"


>--
>Jim Watt
>http://www.gibnet.com

 
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Jim Watt
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      09-09-2005
On 9 Sep 2005 15:01:46 GMT, Unruh <(E-Mail Removed)> wrote:

>Note that children can hear up to about 25KHz. The reason women and kids
>find TVs so annoying is that most are designed by male engineers who are
>completely deaf above about 10KHz, and cannot hear the flyback transformer,
>which on much consumer junk shrieks loudly. Were it 60Hz humm the sets
>would never never have been designed that way, but at 15-17KHz, its "What
>humm?"


15.625Khz for European systems. I used to find it annoying but either
the sets are better designed today or noisy discos and time have taken
their toll. point taken about the aliasing, but filters are good these
days. Live concerts from BBC Radio 3 sound very agreeable thanks
to digital technology, but the footprint does not extend to .ca and
their website only averages a sample rate of 32kbps in total for
stereo in Real Audio which is good - but not hifi.

--
Jim Watt
http://www.gibnet.com
 
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Unruh
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      09-10-2005
Jim Watt <(E-Mail Removed)_way> writes:

>On 9 Sep 2005 15:01:46 GMT, Unruh <(E-Mail Removed)> wrote:


>>Note that children can hear up to about 25KHz. The reason women and kids
>>find TVs so annoying is that most are designed by male engineers who are
>>completely deaf above about 10KHz, and cannot hear the flyback transformer,
>>which on much consumer junk shrieks loudly. Were it 60Hz humm the sets
>>would never never have been designed that way, but at 15-17KHz, its "What
>>humm?"


>15.625Khz for European systems. I used to find it annoying but either


Just ask your wife and kids. It is you.

>the sets are better designed today or noisy discos and time have taken
>their toll. point taken about the aliasing, but filters are good these
>days. Live concerts from BBC Radio 3 sound very agreeable thanks
>to digital technology, but the footprint does not extend to .ca and
>their website only averages a sample rate of 32kbps in total for
>stereo in Real Audio which is good - but not hifi.


The ear is astonishingly accomodating. Ie it will take really crappy sound
( factors of 100 difference in sound levels at verious frequencies and
horrible frequency bandwidth-- ie most portable radios) and deliver what
seems to be quite reasonable sound. It is the ear doing most of the work.
Of course if you compare it to the original, suddenly the deficiencies
become obvious. The ear is a really really amazing instrument.


>--
>Jim Watt
>http://www.gibnet.com

 
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