4 ms·
Keep in mind that 700 b/s is an extremely low bitrate. I worked on Opus, which bottoms out at around 6000 b/s. A typical IP+UDP+RTP packet has 40 bytes of head
by derf_ 10y ago
Keep in mind that 700 b/s is an extremely low bitrate.
I worked on Opus, which bottoms out at around 6000 b/s. A typical IP+UDP+RTP packet has 40 bytes of headers, which with 40 ms frames is 8000 b/s of overhead. Cell networks will use header compression to reduce that, but even so. 8000 b/s is almost eleven and a half 700C codec2 streams.
codec2 is just in another league. It's seriously impressive work.
- nitrogen 10y agoI think the old Crichton novel, Congo, mentioned using a very low bitrate codec over a digital satellite link. So maybe something already exists off the shelf that one could try over amateur radio.
- jdietrich 10y agoAFAIK there aren't any commercial codecs with such low bit rates, as there simply isn't the demand. The minimum bit rate of GSM-AMR is 4.75kbps. Some military codecs designed for use over HF are in the same ballpark as Codec2 - STANAG 4479 operates at 800bps. There is some academic research on voice codecs below 500bps.
- nullc 10y agoFun fact: export of very low bitrate (<2400 bps) codecs has been restricted under the same munitions restrictions as crypto (And also when open source presumably subject to the same court outcomes in the US).
- axman6 10y agoGotta talk to those subs somehow, those ultra long wavelength Comms aren't exactly high bandwidth. (I'm just making this up but it feels plausible, at least a few decades ago)