Radium wrote:
On Aug 19, 10:08 pm, Jerry Avins 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/surp...ab/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 bull**** 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.
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