On Aug 19, 10:08 pm, Jerry Avins <j...@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. Using this video frequency-shifting, a high-quality video can be stored in an extremely slow moving video-cassette with limited amount of tape. Due to the video-tape's extremely slow speed the temporal and spatial frequencies of the incoming video signals must be downshifted in order to be encoded at such slow speeds. Due to the limited length of film in the cassette, the movie must not be made longer than what it originally is. Due to other inadequacies in the film, the spatial- frequency must also be decreased, but the image size must not increase.> > The motion of 'everything else' *is* slowed. However, the playback > > speed remains constant.> Explain how everything can slow town without increasing the time to > complete a motion. Sounds have duration and pitch. motion has no analog > of pitch in that sense. Describe the result you want, not "something > like" the result.A 2 hour high-quality movie should be able to be stored in device with limited high-frequency response and limited amount of storage space. There should be absolutely no aliasing -- temporal or spatial - but at the same time, the length of the movie should not be increased, sizes of objects in images should not increase, image size should not increase and no low-pass filtering should be used.> > Repetitive or cyclical motion (such as a ball bouncing, or a wagon > > wheel rotating, or a bird-flapping its wings, or an exposed model of a > > piston engine operating, or a flag waving in the wind) in the movie > > are slowed without lengthening the clip.> Tell me again how the crankshaft can take run one fifth speed without > using more time to make a turn.I wish I knew. This 'pitch-shifting' is a lot more confusing than I thought. Yet I still find it so interesting. Sorry.> > Sorry that should read "makes a still image less sharp by stretching > > everything within the image without increasing the size of the image > > or eliminating sharp portions of the original image"> Tell me again how everything in an image can be stretched to double size > without making the image twice as big.Nothing in the image has its size increased. They are simply smoothed out. This is similar to a graph of digital audio in Adobe Audition. You decrease the pitch of the audio in the file by half [without changing the tempo] and the waves in the graph will appear twice as long but without increasing the horizontal length of the graph.> > I don't want low-pass filtering. I simply want all frequencies to be > > downshifted similar to decreasing the pitch of audio without slowing > > the playback speed. The analogy is lower the frequencies of all > > components in the image w/out increasing the size of the image or > > doing any low-pass filtering.> >http://www-dse.doc.ic.ac.uk/~nd/surprise_96/journal/vol4/sab/report.html> Justify why you think that images and sounds are subject to the same > transformations.The less sample rate you have in digital audio, the lower the frequency of the audio must be in order to prevent aliasing. There isn't enough bandwidth to include the higher-pitches. Similarly an imaging device with insufficient spatial bandwidth will result in image distortion if excessively fine detail is put into the camera. Hence, if you want to get decent imagery in a low-bandwidth imaging device, your best bet is to decrease the spatial frequency because transferring it into the imaging device. Just like if you have an 11.025-KHz-sample-rate digital audio device, you need to make sure the pitch of the audio you are inputting into the device does not exceed 5.5125 KHz.> > How is it false?> Images have no visual equivalent of pitch. Pitch is temporal. Images are > spatial.Spatial frequency is how fine or dull an image is. Pitch is determined by audio frequency. I am using the spatial frequency as an analogy.
Questions about equivalents of audio/video and digital/analog.
Started by ●August 19, 2007
Reply by ●August 20, 20072007-08-20
Reply by ●August 20, 20072007-08-20
Dave Platt wrote:>> 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.I can buy that, but it's not how I would have used the term. I call a two-state representation "binary". A storage system that is clocked is subject to most of the restrictions and permits most of the useful techniques of digital signal processing. Early transversal filters used op-amps, with the coefficients being set by the resistor values.> In that sense, an audio CCD uses a digital clocking structure to move > the charge along, but uses a non-digital system for representing the > signal level (a linear number of electrons). Yes, it's quantized in > time, and the electron charges themselves are quantized... but I don't > think that either of these qualifies it as "digital".I agree to use your term for the sake of this discussion.> "Analog" is a very fuzzy and imprecise term, and I think that a CCD > can reasonably be called an analog system.Yet I'd lay a bet that you call the pictures made by means of a CCD image sensor "digital".> Even audio cassette tape is quantized in both time and amplitude, at > the level of the individual magnetic domains in the oxide or metal > particles.Oh, sure. In that case, the crystal radio that I built in the 40s was digital too. The electrons came down the antenna one at a time even if closely spaced. We need to draw a line somewhere, and I don't like the idea of calling a flashlight a digital photonic device. There are in principle purely analog storage devices. A loop of analog delay line with a repeater in it qualifies. A memory based on that principle was used to store digital signals in an early computer, even though the device itself is analog. It used an acoustic delay in a column of mercury. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●August 20, 20072007-08-20
On Sun, 19 Aug 2007 23:26:16 -0700, dplatt@radagast.org (Dave Platt) wrote:>"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.My reading of the possible systems goes like this. analogue - a continuous representation of the original signal sampled - a representation of the signal at discrete time points quantized - a sampled signal, but with the possible levels constrained to a limited set of values digital - a quantized signal, with the individual levels represented by numbers Aliasing is going to happen as soon as you move beyond the first line of that list. d -- Pearce Consulting http://www.pearce.uk.com
Reply by ●August 20, 20072007-08-20
On Sun, 19 Aug 2007 23:26:16 -0700, dplatt@radagast.org (Dave Platt) wrote:>"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.My reading of the possible systems goes like this. analogue - a continuous representation of the original signal sampled - a representation of the signal at discrete time points quantized - a sampled signal, but with the possible levels constrained to a limited set of values digital - a quantized signal, with the individual levels represented by numbers Aliasing is going to happen as soon as you move beyond the first line of that list. d -- Pearce Consulting http://www.pearce.uk.com
Reply by ●August 20, 20072007-08-20
On Sun, 19 Aug 2007 23:26:16 -0700, dplatt@radagast.org (Dave Platt) wrote:>"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.My reading of the possible systems goes like this. analogue - a continuous representation of the original signal sampled - a representation of the signal at discrete time points quantized - a sampled signal, but with the possible levels constrained to a limited set of values digital - a quantized signal, with the individual levels represented by numbers Aliasing is going to happen as soon as you move beyond the first line of that list. d -- Pearce Consulting http://www.pearce.uk.com
Reply by ●August 20, 20072007-08-20
Radium wrote:> On Aug 19, 10:08 pm, Jerry Avins <j...@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.If you have a purpose in mind, you must have a pretty good idea of what it does. If you can make that clear, we might have something to discuss.> Using this video frequency-shifting, a high-quality video can be > stored in an extremely slow moving video-cassette with limited amount > of tape. Due to the video-tape's extremely slow speed the temporal and > spatial frequencies of the incoming video signals must be downshifted > in order to be encoded at such slow speeds. Due to the limited length > of film in the cassette, the movie must not be made longer than what > it originally is. Due to other inadequacies in the film, the spatial- > frequency must also be decreased, but the image size must not > increase.More arm waving. Tell me how you think it might be accomplished. (Hint: it sounds like nonsense to me. One of those revelatory dreams that seem so clear until I wake up.>>> The motion of 'everything else' *is* slowed. However, the playback >>> speed remains constant. > >> Explain how everything can slow town without increasing the time to >> complete a motion. Sounds have duration and pitch. motion has no analog >> of pitch in that sense. Describe the result you want, not "something >> like" the result. > > A 2 hour high-quality movie should be able to be stored in device with > limited high-frequency response and limited amount of storage space. > There should be absolutely no aliasing -- temporal or spatial - but at > the same time, the length of the movie should not be increased, sizes > of objects in images should not increase, image size should not > increase and no low-pass filtering should be used."Should" is an interesting word. It can prescribe and it can express an expectation or desire. In this case, your desire is contrary to my expectation.>>> Repetitive or cyclical motion (such as a ball bouncing, or a wagon >>> wheel rotating, or a bird-flapping its wings, or an exposed model of a >>> piston engine operating, or a flag waving in the wind) in the movie >>> are slowed without lengthening the clip. > >> Tell me again how the crankshaft can take run one fifth speed without >> using more time to make a turn. > > I wish I knew. This 'pitch-shifting' is a lot more confusing than I > thought. Yet I still find it so interesting. Sorry.Don't be sorry. If you work out the details, I'll help you to see the inherent contradictions they impose, but I won't argue with you about it.>>> Sorry that should read "makes a still image less sharp by stretching >>> everything within the image without increasing the size of the image >>> or eliminating sharp portions of the original image" > >> Tell me again how everything in an image can be stretched to double size >> without making the image twice as big. > > Nothing in the image has its size increased. They are simply smoothed > out. > > This is similar to a graph of digital audio in Adobe Audition. You > decrease the pitch of the audio in the file by half [without changing > the tempo] and the waves in the graph will appear twice as long but > without increasing the horizontal length of the graph. > >>> I don't want low-pass filtering. I simply want all frequencies to be >>> downshifted similar to decreasing the pitch of audio without slowing >>> the playback speed. The analogy is lower the frequencies of all >>> components in the image w/out increasing the size of the image or >>> doing any low-pass filtering. > >>> http://www-dse.doc.ic.ac.uk/~nd/surprise_96/journal/vol4/sab/report.html > >> Justify why you think that images and sounds are subject to the same >> transformations. > > The less sample rate you have in digital audio, the lower the > frequency of the audio must be in order to prevent aliasing. There > isn't enough bandwidth to include the higher-pitches. > > Similarly an imaging device with insufficient spatial bandwidth will > result in image distortion if excessively fine detail is put into the > camera.That's true only if you mean spatial aliasing. Otherwise, you're using "distortion" in a non-standard way.> Hence, if you want to get decent imagery in a low-bandwidth imaging > device, your best bet is to decrease the spatial frequency because > transferring it into the imaging device.More nonsense. Think about it and tell me why.> Just like if you have an 11.025-KHz-sample-rate digital audio device, > you need to make sure the pitch of the audio you are inputting into > the device does not exceed 5.5125 KHz.How does that make for "decent imagery? It amounts to a low-pass filter, about which you remarked, "ugh".>>> How is it false? > >> Images have no visual equivalent of pitch. Pitch is temporal. Images are >> spatial. > > Spatial frequency is how fine or dull an image is. Pitch is determined > by audio frequency. I am using the spatial frequency as an analogy.Stop with analogies. Say what you mean. Here's the picture of you that I have in my head: You were a precocious kid, and impressed those around by asking questions that were further out than what most kids asked. (Reading a lot leads one to do that.) The adults around you patted you on the head and praised you for digging into subjects they knew little or nothing about.* They knew so little about it that they didn't understand much of what you talked about, and so couldn't set you back on the rails when you wandered away from reality. No matter, the praise kept coming anyway, and you learned that if you imagined something, it was golden. It wasn't really, but those around you taught you to believe that it was. Now you find yourself going on about your imaginings with people who _do_ understand the subject you fantasize about and their reaction hurts, but you're finding it very hard to get out of bullshit mode and ask basic questions. It hasn't sunk in yet that you don't even have basic answers because you still believe that the fantasies you construct are real. I hope you get over that. In the meanwhile, I feel sorry for you. Jerry ___________________________________ * From Gilbert and Sullivan's /Patience/: "If this young man expresses himself in terms too deep for me/ Why what a very singularly deep young man/ This deep young man must be" Your type has been mocked a long time. -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●August 20, 20072007-08-20
On Sun, 19 Aug 2007 18:14:58 -0700, Radium <glucegen1@gmail.com> wrote:>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?Because if it could, there would be no need to invent digital which has the advantage of non-moving parts.................... -m- -- Official website "Jonah's Quid" http://www.jonahsquids.co.uk
Reply by ●August 20, 20072007-08-20
On Sun, 19 Aug 2007 20:54:06 -0700, dplatt@radagast.org (Dave Platt) wrote:>Another sort of a purely analog signal-storage device, with no moving >parts other than the electrons which convey the signal, is a simple >length of transmission lineHere is a better one: transmit the analogue system to the sun, and you have 16 minute, once-of storage. If you want to save your recording for a longer time, you can pick more planets and stars, further away, and bounce your radiosignal off them. It is obviously not random-access, but it is very analogue. -m- -- Official website "Jonah's Quid" http://www.jonahsquids.co.uk
Reply by ●August 20, 20072007-08-20
Don Pearce wrote:> On Sun, 19 Aug 2007 23:26:16 -0700, dplatt@radagast.org (Dave Platt) > wrote: > >> "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. > > My reading of the possible systems goes like this. > > analogue - a continuous representation of the original signal > sampled - a representation of the signal at discrete time points > quantized - a sampled signal, but with the possible levels constrained > to a limited set of values > digital - a quantized signal, with the individual levels represented > by numbers > > Aliasing is going to happen as soon as you move beyond the first line > of that list.I like your categories. It is possible in concept to have a signal that is quantized in magnitude and continuous in time, but (unless we resort to counting electrons) I don't think it's possible in practice. jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●August 20, 20072007-08-20
Don Pearce wrote:> On Sun, 19 Aug 2007 23:26:16 -0700, dplatt@radagast.org (Dave Platt) > wrote: > >> "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. > > My reading of the possible systems goes like this. > > analogue - a continuous representation of the original signal > sampled - a representation of the signal at discrete time points > quantized - a sampled signal, but with the possible levels constrained > to a limited set of values > digital - a quantized signal, with the individual levels represented > by numbers > > Aliasing is going to happen as soon as you move beyond the first line > of that list.I like your categories. It is possible in concept to have a signal that is quantized in magnitude and continuous in time, but (unless we resort to counting electrons) I don't think it's possible in practice. jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
