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Author: RadiumRadium Date: Aug 19, 2007 18:46
On Aug 19, 6:08 pm, Jerry Avins ieee.org> wrote:
> Radium wrote:
>> This would be a start if I want to decrease the frequency of a video
>> signal without decreasing the playback speed.
> Various compression schemes do that with varying degrees of resulting
> quality.
I am talking about:
1. Decreasing the temporal frequency of the video signal without low-
pass filtering or decreasing the playback speed - an example of which
would be decreasing the rate at which a bird [in the movie] flaps its
wings. Hummingbirds flap their wings too fast for the human eye to
see. So the flap-rate of the wings could be decreased until the
flapping is visible to the human eye - without decreasing the playback
speed of the video. This decrease in flap-rate without slowing
playback is visually-analogous to decreasing the pitch of a recorded
sound without decreasing the playback speed. In this case, low-pass
filter would involve attenuating rapidly-changing images while
amplifying slowly-changing images -- I don't want this.
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Author: Jerry AvinsJerry Avins Date: Aug 19, 2007 19:47
Radium wrote:
> On Aug 19, 5:55 pm, Jerry Avins ieee.org> wrote:
...
>> Ir color differentiation. Or both.
>
> Huh?
Typo: Or color differentiation. Or both.
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Author: Jerry AvinsJerry Avins Date: Aug 19, 2007 19:59
Radium wrote:
> On Aug 19, 6:08 pm, Jerry Avins ieee.org> wrote:
> >> Radium wrote:
>
>>> This would be a start if I want to decrease the frequency of a video
>>> signal without decreasing the playback speed.
>
>> Various compression schemes do that with varying degrees of resulting
>> quality.
>
> I am talking about:
>
> 1. Decreasing the temporal frequency of the video signal without low-
> pass filtering or decreasing the playback speed - an example of which
> would be decreasing the rate at which a bird [in the movie] flaps its
> wings. Hummingbirds flap their wings too fast for the human eye to
> see. So the flap-rate of the wings could be decreased until the
> flapping is visible to the human eye - without decreasing the playback
> speed of the video. This decrease in flap-rate without slowing ...
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Author: RadiumRadium Date: Aug 19, 2007 20:04
On Aug 19, 7:47 pm, Jerry Avins ieee.org> wrote:
> Radium wrote:
>> Other than the microphone [obviously], why does there need to be any
>> moving parts? If a digital audio device can play audio back without
>> any moving parts, why can't an analog audio device be designed to do
>> the same?
> Describe a motion-free process of recording and playing back. Cutting
> grooves on a disk or magnetizing a moving tape both involve motion.
The iPod is motion-free yet it's still able to record and playback.
Those Nintendo Entertainment System cartridges were able to playback
without any motion.
>> The device below is *not* analog. It uses sampling so its digital:
>> I'm curious to why there are no purely-analog devices which can
>> record, store, and playback electric audio signals [AC currents at
>> least 20 Hz but no more than 20,000 Hz] without having moving parts.
>> Most of those voice recorders that use chips [i.e. solid-state] are
>> digital. Analog voice recorders, OTOH, use cassettes [an example of
>> "moving parts"].
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Author: Sjouke BurrySjouke Burry Date: Aug 19, 2007 20:16
Radium wrote:
> On Aug 19, 7:47 pm, Jerry Avins ieee.org> wrote:
> >> Radium wrote:
>
>>> Other than the microphone [obviously], why does there need to be any
>>> moving parts? If a digital audio device can play audio back without
Ah Radium trolling again i see!!!!
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Author: Ron N.Ron N. Date: Aug 19, 2007 20:27
someone wrote:
> There is no analog-equivalent of sample-rate? Then what the limits the
> highest frequency an analog audio device can encode?
>
> What determines the highest frequency signal an analog solid-state
> audio device can input without distortion?
The basic physics of material objects leads to some
limitations. At some frequency, a given force can
no longer accelerate the mass of a given physical
transducer or recording substance by an amount
greater than does thermal noise (and other sources
of noise, such as friction, wear, dust, magnetic
particle size, film grain size, etc.)
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Author: Bob MyersBob Myers Date: Aug 19, 2007 20:34
>In the case of digital video, we could treat each individual sample
>point location in the sampling grid (each pixel position in a frame)
>the same way as if it was a sample from an individual (mono) audio
>signal that continues on the same position in the next frame. For
>example, a 640
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Author: Jerry AvinsJerry Avins Date: Aug 19, 2007 20:37
Radium wrote:
> On Aug 19, 7:47 pm, Jerry Avins ieee.org> wrote:
> >> Radium wrote:
>
>>> Other than the microphone [obviously], why does there need to be any
>>> moving parts? If a digital audio device can play audio back without
>>> any moving parts, why can't an analog audio device be designed to do
>>> the same?
>
>> Describe a motion-free process of recording and playing back. Cutting
>> grooves on a disk or magnetizing a moving tape both involve motion.
>
> The iPod is motion-free yet it's still able to record and playback.
It does that digitally. Did you really not know that? Are you trolling
after all?
> Those Nintendo Entertainment System cartridges were able to playback
> without any motion.
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Author: Jerry AvinsJerry Avins Date: Aug 19, 2007 20:51
Bob Myers wrote:
> ... you must sample the
> original signal at a rate equal to at least twice its bandwidth (actually,
> very slightly higher, to avoid a particular degenerate case which
> could occur at EXACTLY 2X the bandwidth) in order to preserve
> the information in the original and avoid "aliasing."
Bob,
The degenerate case is just a limit. Signals close to the band edge take
a long time to be resolved. The time is of the order if 1/|f-F|, where F
is the frequency of the nearer band edge. Just as it takes in the order
of 100 seconds to resolve a frequency of .01 Hz, it takes the same time
to resolve a frequency of Fs/2 - .01 Hz. When f = Fs/2, it just takes
forever. The real works tends to be continuous.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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Author: Dave PlattDave Platt Date: Aug 19, 2007 20:54
>I'm curious to why there are no purely-analog devices which can
>record, store, and playback electric audio signals [AC currents at
>least 20 Hz but no more than 20,000 Hz] without having moving parts.
>Most of those voice recorders that use chips [i.e. solid-state] are
>digital. Analog voice recorders, OTOH, use cassettes [an example of
>"moving parts"].
The fact that it's an AC (inherently-varying) signal being recorded,
means that *something* has to move... if only some amount of
electrical charge. If the electrons don't move, the output can't vary
and all you have is a DC voltage.
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