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1200 baud data transfer over audio passband of cellphone. Is that possible?
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TheUnnamedNewbie:
Audio on a cellphone tends to also be compressed in very specific ways that are optimized for voice (which is why the 'please wait' music with callcenters is so horrible). I suspect you will find it very hard to send any data through it as it too will be crazy deformed by the codecs.
sv3ora:
I have encountered this situation you mention, only on remote areas where there is no good signal, or when I used very old phones (1998 era). Dropouts of audio parts or "pixelated" sounds in some audio parts. I have not come across similar situations when there is a good signal.

Note, for FSK, audio amplitude compression should be less critical, as it is the frequency of the tones that matter.
TheUnnamedNewbie:

--- Quote from: sv3ora on October 29, 2019, 12:14:19 pm ---Note, for FSK, audio amplitude compression should be less critical, as it is the frequency of the tones that matter.

--- End quote ---

Don't most audio compression algorithms do a lot of stuff in frequency/wavelet domain where frequencies/wavelets that are considered secondary to the main few peaks are just removed?
ogden:

--- Quote from: TheUnnamedNewbie on October 29, 2019, 12:07:21 pm ---I suspect you will find it very hard to send any data through it as it too will be crazy deformed by the codecs.

--- End quote ---
Not true. Speech indeed is spoken *data*. Question here is how to modulate digital data such a way that speech codecs do not affect audio signal during transmission.
sv3ora:

--- Quote from: ogden on October 29, 2019, 12:30:12 pm ---Question here is how to modulate digital data such a way that speech codecs do not affect audio signal during transmission.

--- End quote ---
Precisely!

I think I am going to do the test with the MixW modem to see what will happen. We may come across pleasant discoveries...or not.
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