"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:53gtfeF1qi934U1@mid.individual.net...
> And limiting the bandwidth is a form of "data compression".
> It was invented before our grandparents were born in
> the days of early telephony.

No, you are simply misusing the term "compression".
By your definition *everything* that does not include DC-infinity (ie.
everything full stop) is therefore "compressed".
Good luck with getting that generally accepted as a new definition.

MrT.

Jerry Avins wrote:
> 
> Engineering is the art of making what you want from things you can get.


   That is also the definition of "Creative recycling". :-)


-- 
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Richard Crowley wrote:

   ...

> And limiting the bandwidth is a form of "data compression".
> It was invented before our grandparents were born in
> the days of early telephony. 

Call it data reduction if you wish. "Compression" is generally given a 
more restricted meaning.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

"Mr.T" wrote ...
>
> "Richard Crowley"  wrote ...
>> Selecting a sample rate always performs some sort of
>> "compression".
>
> Not at all. Compression involves a manipulation of data *within* the range
> under consideration. (either lossy compression or lossless)
> If extraneous data falls completely outside the required range, then no
> compression is necessary within that range.
>
>> One could argue that setting the sample
>> rate of audio merely selects what you want your HF
>> cutoff to be.
>
> No, there would be no *real* argument at all, since that *is* what it 
> does.


And limiting the bandwidth is a form of "data compression".
It was invented before our grandparents were born in
the days of early telephony. 

"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:53eq2sF1rcdkaU1@mid.individual.net...
> Selecting a sample rate always performs some sort of
> "compression".

Not at all. Compression involves a manipulation of data *within* the range
under consideration. (either lossy compression or lossless)
If extraneous data falls completely outside the required range, then no
compression is necessary within that range.

> One could argue that setting the sample
> rate of audio merely selects what you want your HF
> cutoff to be.

No, there would be no *real* argument at all, since that *is* what it does.

MrT.

glen herrmannsfeldt wrote:
> Ron N. wrote:
> 
> (snip)
> 
>> As for storing uncompressed formats, didn't amateur radio
>> types try storing monochrome (very) slow scan video on
>> audio tape?
> 
> There was a story in Popular Science many years ago that I
> still remember about storing fast scan (normal TV) video
> on 0.25 inch audio tape.  It ran the tape at 120in/s,
> with the cover page of the story showing the results after
> the tape breaks.  They heat the record/play head to reduce
> friction.  10 inch tape reels were normally used to get a
> reasonable time.   I don't believe it ever got popular.
> 
> -- glen
> 
I used to use 2" wide (so far more robust) instrumentation tape at 120 
inches/second. The drives used air bearing guides, to reduce friction, 
but dragged the tape across ordinary heads with no special method of 
dealing with heat or friction. They did have elaborate arrangements to 
stabilise the tape as it passed over the heads, though. A 15" reel of 
tape ran for about 16 minutes, and had 24 or 28 tracks. Those drives 
used to be the mainstay of instrumentation in a number of fields (mostly 
military). They could put a fair quality TV picture onto each of their 
24 tracks. Several people made drives of that kind - Ampex, Honeywell, 
Enertec, and others. We used to fly compact versions, while large floor 
standing ones were used in the lab.

So, the popular science article was not describing anything crazy. I 
just wonder about handling 0.25" tape at that speed.

Regards,
Steve

glen herrmannsfeldt wrote:

> There was a story in Popular Science many years ago that I
> still remember about storing fast scan (normal TV) video
> on 0.25 inch audio tape.  It ran the tape at 120in/s,
> with the cover page of the story showing the results after
> the tape breaks.  They heat the record/play head to reduce
> friction.  10 inch tape reels were normally used to get a
> reasonable time.   I don't believe it ever got popular.
> 

When I was a kid, I was trying to record the video signal from TV to a 
modified conventional cassette tape recorder. For that purpose, the 
recorder was operating in the fast forward mode, so the tape speed was 
about 2m/s. I was able to establish the horizontal and vertical sync,and 
even to see something, however I woudn't call this a picture.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

Ron N. wrote:

(snip)

> As for storing uncompressed formats, didn't amateur radio
> types try storing monochrome (very) slow scan video on
> audio tape?

There was a story in Popular Science many years ago that I
still remember about storing fast scan (normal TV) video
on 0.25 inch audio tape.  It ran the tape at 120in/s,
with the cover page of the story showing the results after
the tape breaks.  They heat the record/play head to reduce
friction.  10 inch tape reels were normally used to get a
reasonable time.   I don't believe it ever got popular.

-- glen

"Ron N." wrote ...
> "Richard Crowley"  wrote:
>> CCIR 601 appears to be 4:2:2   That means that the
>> chrominance data is compressed 2:1
>
> Only if you regard reducing the sample rate as a
> form of compression.

If it weren't compression, they wouldn't bother doing it.

> But then your typical 44.1kHz audio CD has also likely
> been reduced in sample rate from 48 or 96 kHz as
> recorded in the studio.  Is that compression?

Many would say "yes".

> Or just an appropriate choice of filtering and data format?

Selecting a sample rate always performs some sort of
"compression". One could argue that setting the sample
rate of audio merely selects what you want your HF
cutoff to be.

OTOH, purposely digitally sub-sampling (or analog band-
width-limiting) the color part of the image is a data-saving
perceptual shell game similar to the lossy compression
done by MP3, AAC, Ogg, et.al.

> The chrominance in 601 is reduced to a bandwidth
> that better matches the typical human perceptual
> bandwidth of the luminance channel.

And yet the casual observer can tell the difference
between full-bandwidth RGB and reduced-color rez
video transmission schemes when viewed side-by-
side. 

On Feb 13, 1:09 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:
> "Norbert Hahn" wrote ...
>
> > "Radium"  wrote:
> >>"Mr.T" wrote:
> >>> It would be nice if there was one single video format as common as CD
> >>> audio
> >>> I guess. The nearest equivalent would obviously be standard DVD,
> >>> MPEG-II,
> >>> but unfortunately you still have the country dependant format variations
> >>> for
> >>> frame size and frame rate etc.
>
> >>Um, MPEG is compressed. I was looking for uncompressed digital video.
>
> > Have a look athttp://en.wikipedia.org/wiki/CCIR_601
>
> > This is closest to raw digital video.
>
> CCIR 601 appears to be 4:2:2   That means that the
> chrominance data is compressed 2:1

Only if you regard reducing the sample rate as a
form of compression.  But then your typical 44.1kHz
audio CD has also likely been reduced in sample rate
from 48 or 96 kHz as recorded in the studio.  Is
that compression?  Or just an appropriate choice
of filtering and data format?

The chrominance in 601 is reduced to a bandwidth
that better matches the typical human perceptual
bandwidth of the luminance channel.


IMHO. YMMV.