The audio session opens its TX side alongside RX (txenable in the conninfo,
16 kHz both ways), the stream gains a paced sender — 320 samples every 20 ms,
the frame mirroring what the rig itself sends on this socket, IDs swapped —
and the network Icom takes the same NetworkPlayer slot a TCI radio does: pick
'Radio (network audio)' as the To-radio device and the voice keyer needs no
cable and no virtual sound card. PTT brackets the message through the same
code as every other audio path.
The radio now appears as a device in both audio lists — 'Radio (TCI
network audio)' — so the receive audio and the voice keyer can both take
the CAT link instead of a sound card. No virtual cable, no second card, no
Windows mixer between the recording and the air.
The transmit side reuses the exchange the tone probe established, with a
WAV in place of the sine: the radio asks, we answer with the next slice,
and it sets the pace. The message is converted once, up front, rather than
per frame — a voice message is a few hundred kilobytes, and resampling
inside a callback that has 21 ms to answer would put arithmetic on the
path where a late frame is a gap on the air.
The PTT is untouched by all this: the keyer keys before and unkeys after
exactly as it does with a sound card, so a transmission is bracketed by
the same code whichever way the audio travels. And the playback runs OFF
the CAT goroutine, since everything else about the rig goes through that
one place and a ten-second message would otherwise freeze the frequency
display and the antenna following for ten seconds.
Two refusals rather than silent failure. A radio that has gone away stops
being offered as a device at all, and a radio whose transmit audio source
is still the microphone is caught within a fifth of a second — a voice
keyer that transmits silence is worse than one that says why it will not.
rouggy