ITTY is sampling the audio at 11025Hz, 16 bits per sample, mono. When I tried going lower some said they were having trouble. I could easily try it again, but that’s where it stood a few years ago and I’ve not touched it since.
8 bit/8kHz would be an interesting test! I’m all for using less bandwith. Maybe I’ll try this on the 100WPM channel and let the users who are using it tell me how it goes. If anyone wants to be in on this test (100WPM) let me know and we will give it a whirl. If it works there, I can move the lower sampling over to the 60WPM channels.
And if you all twist my arm, we can do the test on the 60WPM channel to start with.
On Sep 23, 2021, at 10:09 AM, Harold Hallikainen <harold@w6iwi.org> wrote:
Methods of doing AFSK Internet broadcasts like ITTY are interesting. Ithought the idea of splicing together mark and space tone files was veryclever.I wonder about the need for audio compression. I did a microcontrollerproject that streamed live audio using ADPCM and PCM. The PCM used 16 bitsamples at 44.41 kHz. But, I think for RTTY, 8 bit samples at 8 kHz shouldbe fine (since that's what circuit switched telephone uses). In myapplication, on receiving the HTTP request, I sent the WAV header with avery large file size, then just started sending the samples.As mentioned, I do think the splicing of tone files is very clever!Another method that would be interesting is direct digital synthesis.Depending on the desired frequency, each successive sample would be somenumber of steps through a sine table from the previous sample.Anyway, interesting stuff!Harold______________________________________________________________GreenKeys mailing listHome: http://mailman.qth.net/mailman/listinfo/greenkeysHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:GreenKeys@mailman.qth.netJordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
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