[tor-talk] TOR Fone - p2p secure and anonymous VoIP tool

[Fabio Pietrosanti (naif)]

On 2/3/13 9:23 PM, coderman wrote:
> "push-to-talk" with procedure words over zrtp would be applicable. use
> FEC to accommodate reasonable loss over datagram Tor.
>
> both Whisper Systems and Guardian Project are working on PTT
> capabilities, iirc.
>
> last but not least, the codec makes no difference until larger issues
> are worked out, for those arguing about OPUS vs. G729a/729.1 vs Speex,
> etc. in practice the G729 implementations in cSipSimple (over ZRTP)
> seem to be best, but this is most likely the other implementations
> sucking. i have high hopes for a better OPUS codec...

For my daily-for-profit-job i made in past stuff for secure telephony
over GPRS that:
- can have variable latencies on CS1 between 800ms-2200ms
- is a reliable transport (the low level of the OS does retransmissions
at GSM RLP level)

To work over high latency (and tipically also low-bandwidth) with
reliable transport (like TCP/Tor) you need to use those multimedia strategy:
- setup a large static jitter buffer (you define the added artificial
latency of the call to compensate variable latency)
- reduce transport protocol overhead by setting a large "packetization time"
- detect retransmission behaviours, in that case apply small TX cutting
(transmission)

With such approach you can avoid "PTT" and even if the communication
will sounds like an old analog satellite connection, it works.

Fabio
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