try looking up Frequency Shift Keying (FSK)
Cheers,
CW
Ra dium wrote:
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17 years ago
FM Video -- Compression and "backbone"
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- posted
17 years ago
Bob Eld wrote in
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Simple answer: FM is wasteful of bandwidth with other things equal. The
> video signal needs about 3-1/2Mhz of bandwidh. It would be difficult to get
> this with FM unless the channel spacing was maybe 10 to 20MHz depending on
> modulation index.
What if the WMV [Windows Media Video] digital compression is used and the color resolution is decrease sufficiently? Its possible to have a supreme quality in terms of number of pixels and frame rate. All you have to do is compress the WMV's color resolution and you can get a bit-rate that is low enough not to hog bandwidth.
Also note that digital modulation is also AM where the phase also carries
> information. There are many modulation schemes such as QAM, etc. but they
> all use AM as the backbone.
Does this mean PCM is also AM at heart? Analog signal is converted to PAM [pulsatile version of AM]. This PAM is then converted to PCM
Is it possible for digital modulation to use FM as a backbone? Has this ever been done?
What about converting to analog signal to PFM and then PCM [or the "FM equivalent" of PCM]? Has this been done before?
What is the "FM equivalent of PCM"? [as you say, PCM uses AM as a "backbone"]
Thanks,
Radium
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17 years ago
Chris Welsh try looking up Frequency Shift Keying (FSK)
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AFAIK, Frequency-Shift-Keying is used in 1-bit only. One represent a certain frequency, zero represents another frequency. What if I want
32-bit digital FM?- Vote on answer
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17 years ago
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Read up some more of FSK, also read up on PSK especially O-QPSK. Here are some links you may find interesting.
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17 years ago
-- Sure. FSK.
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17 years ago
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-- You can also use the absence of an output to represent a zero. f1 f2 data -----+-----+------ off off 00 off on 01 on off 10 on on 11 > What if I want 32-bit digital FM?