> Radium wrote:

>> 2. Decreasing the spatial frequency of the images in the video-signal
>> without low-pass filtering the images or increasing their sizes. An
>> example of this would be making the sharp areas of...

> Sampled analog systems are certainly
> not very common today (unless you count certain forms of
> modulation as "sampling," and in fact there are some very close
> parallels there), but the theory remains the same no matter which
> form of encoding is used. In any event, 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."

> On Aug 19, 7:59 pm, Jerry Avins ieee.org> wrote:
>

>> Radium wrote:

>

>>> 2. Decreasing the spatial frequency of the images in the video-signal
>>> without low-pass filtering the images or increasing their sizes. An
>>> example of this would be making the sharp areas of an image look
>>> duller without decreasing the "sharpness" setting [an example of low-
>>> pass filtering] on the monitor or increasing the size of the image.
>>> Normally, when the size of an image is decreased, its sharpness
>>> increases [it's like compressing a lower-frequency sound wave into a
>>> higher-frequency one]. Likewise, when the size of an image is
>>> increased, it looks duller [like stretching a higher-frequency sound
>>> wave into a lower-frequency one]. Low-pass filtering simply decreasing
>>> the sharpness of an image while increasing its dull characteristics --
>>> which is what I don't want.

>

>> That's a reasonable summary of what you don't want to do. What do you
>> think you might do instead? ...

> On Aug 19, 8:34 pm, "Bob Myers" wrote:
>

>> Sampled analog systems are certainly
>> not very common today (unless you count certain forms of
>> modulation as "sampling," and in fact there are some very close
>> parallels there), but the theory remains the same no matter which
>> form of encoding is used. In any event, 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."

>
> Is the CCD [Charge Coupled Device] a "sampled analog system"?

> 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.

> And, in fact, this concept of moving electrical charges is the basis
> for one type of analog signal storage and playback device which has no
> moving (mechanical) parts... the CCD, or Charge Coupled...

>Come on, Dave, a CCD is a digital device, subject to aliasing. The
>charges represent the signal at a particular instant of its average over
>a particular interval. (My CCD digital camera can take time exposures.)
>A CCD's content may not be quantized in amount, but it is quantized in
>time. In a camera, where the charges pertain to individual pixels, the
>result is also quantized in space.

> Radium wrote:

>> The video-equivalent of changing the 'pitch' of audio recording
>> without changing the playback speed.

> That's just arm-waving words. Describe the result, not as an analogy,
> but as a specification. If it turns out that you can't think critically
> after all, I have no time for you.

>> Come on, Dave, a CCD is a digital device, subject to aliasing. The
>> charges represent the signal at a particular instant of its average over
>> a particular interval. (My CCD digital camera can take time exposures.)
>> A CCD's content may not be quantized in amount, but it is quantized in
>> time. In a camera, where the charges pertain to individual pixels, the
>> result is also quantized in space.

>
> "Digital" and "subject to aliasing" are two different things.
>
> As I believe the term "digital" is usually meant, it implies a
> two-state (on/off) storage representation. It's not just that the
> signal amplitude is quantized, but that the quantization uses a
> power-of-two representation and storage system of some sort.

>"Digital" and "subject to aliasing" are two different things.
>
>As I believe the term "digital" is usually meant, it implies a
>two-state (on/off) storage representation. It's not just that the
>signal amplitude is quantized, but that the quantization uses a
>power-of-two representation and storage system of some sort.

> On Aug 19, 10:08 pm, Jerry Avins ieee.org> wrote:
>

>> Radium wrote:

>

>>> The video-equivalent of changing the 'pitch' of audio recording
>>> without changing the playback speed.

>

>> That's just arm-waving words. Describe the result, not as an analogy,
>> but as a specification. If it turns out that you can't think critically
>> after all, I have no time for you.

>
> The purpose of this visual "pitch-shifting" is like a way to record/
> playback/transmit/receive/store supreme-quality video while using the
> least bandwidth and storage space necessary when low-pass filtering is
> not an option.