Re: Questions about equivalents of audio/video and digital/analog.
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Re: Questions about equivalents of audio/video and digital/analog.         

Group: rec.video.desktop · Group Profile
Author: Jerry Avins
Date: Aug 19, 2007 16:39

Radium wrote:
> Hi:
>
> I. Audio vs. Video
>
> Digitized (mono) audio has a single sample per each sampling
> interval.

Yes. several bits per sample, many samples per second.
> 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�480 pixel video stream shot at 30 fps would be treated
> mathematically as if it consisted of 307200 parallel, individual mono
> audio streams [channels] at a 30 Hz sample rate. Where does bit-
> resolution enter the equation?

It might actually make sense to look at it that way in some situations,
but I'll bet you can't think of one. As for bit resolution, what does
that term mean to you? I think it means the number of bits used to
represent each sample, whatever the situation.
> Digital linear PCM audio has the following components:
>
> 1. Sample rate [44.1 KHz for CD audio]

One particular kind of audio. Common uncompressed audio rates range from
8 to 96 KHz.
> 2. Channels [2 in stereo, 1 in monaural]

Up to 5 in home theater systems.
> 3. Bit-resolution [16-bit for CD audio]

So you do know what the term means. Why did you ask then? Easier than
thinking?
> Sample rate in audio = frame rate in video

Bullshit.
> Channel in audio = pixel in video

Bullshit.
> Bit-resolution in audio = ? in video

Bit resolution.
> Is it true that unlike the-frequency-of-audio, the-frequency-of-video
> has two components -- temporal and spatial?

Good question. The signal has a frequency spectrum. A still image has a
spatial spectrum. A video signal represents a series of still images.
> AFAIK, the-frequency-of-audio only has a temporal component. Do I
> guess right?

Yes, until the sound gets into a room. then it has a spatial element
too. Think reflections and standing waves.
> II. Digital vs. Analog
>
> Sample-rate is a digital entity. In a digital audio device, the sample-
> rate must be at least 2x the highest intended frequency of the digital
> audio signal. What is the analog-equivalent of sample-rate? In an
> analog audio device, does this equivalent need to be at least 2x the
> highest intended frequency of the analog audio signal? If not, then
> what is the minimum frequency that the analog-equivalent-of-sample-
> rate must be in relation to the analog audio signal?

There are no samples in an analog system, so there is no sample rate.
> III. My Requests:
>
> No offense but please respond with reasonable answers & keep out the
> jokes, off-topic nonsense, taunts, insults, and trivializations. I am
> really interested in this.

Look, guy: you could probably read by the time you were three years old.
Bully for you! (Precocious reading is almost a /sine qua non/ of
Asperger's.) I have news for you: growing up _doesn't_ mean that one
stops reading. Get a good book or read some of the on-line material
collected at http://www.dspguru.com/ and learn the basics of your
interest. Above all, stop guessing and extrapolating from an erroneous
model that you dreamed up from partial information. You may be smart in
some ways, but if you were wise, you would know that your believing
something doesn't make it real.

As for those snide remarks you want to deflect, you earned them with
your pig-headed pursuit of arrant nonsense. I'm willing to start over,
but I expect you to shape up.

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