Dear Jeroen Vreeken, I'am out of office from March 24 to April 03, 2017. All your messages will be proceeded as soon as possible. Please forward your urgent requests to: +7 (812) 644-0430 #1290
Sorry for inconveniences. Sergei Lebedev mailto:l...@supertel.ru Уважаемый Jeroen Vreeken, Моя почта работает в режиме автоответчика. Меня не будет в офисе c 24 марта по 03 апреля; я отвечу на Ваше письмо как только смогу сделать это. По срочным вопросам прошу Вас звонить: (812) 644-0430 доб.1290 - Вам ответят мои коллеги. Простите за неудобства, Сергей Лебедев mailto:l...@supertel.ru ph: (812) 644-0430 (добавочный 1290 ) fax: (812) 497-3682 ========================================= Saturday, April 1, 2017, 4:02:30 AM, you wrote: > I use a similar trick when I mix voice and data in FreeDV mode 2400B. > But the detection is a bit simpler: Just look at the 'energy' component > of the vocoder. > If the energy of a frame is low and there is data to send the data > will be send and the receiver will inject a bit of silence. > Regards, > Jeroen > On 04/01/2017 01:43 AM, Steve wrote: > > > I was playing with the pairphone modem, and it dawned on me > that the software was using this modem to send both vocoder > data and control data. It did this based on the boolean bit > for VAD. Well, that's probably not novel, but I asked > myself, how the heck could they know when the vocoder output was > speech or noise?? > > Well, it turns out that there is an algorithm just for that > purpose. It looks at each vocoder frame and a little history > and bada-boom youse gotta VAD bit. > > I was trying to figure out how they squeezed all the > encryption information and voice into 1200 bit/s, if the voice > itself was 1200 bit/s! Aha, they look for breaks in the voice and send > control bits instead. > > I suspect there are quite a few frames with no voice. If a > person was looking up something, they might not say anything > while they were otherwise tasked. This probably results in an > excess of control information. Dumb data just to fill the void. > > They almost need something like a duration detector, and > then send text data. A private SMS below the voice and control. > > Have a good weekend, > 73/steve > > > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > > > > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > ========================================= ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
