Delay between PTT assertion and audio packet - Causes dead air for seconds #194
Description
I looked through the issues, and was surprised not to see this anywhere. I had the same problem the last time I tried Direwolf a few years ago.
What happens is on SOME digipeated and beacon transmissions, there is a long delay between when the PTT is asserted and when the audio comes out of the sound card. Yet most transmission are very quick (no obvious delay). I have played around with the DWAIT, TXDELAY, and TXTAIL, and they don't seem to affect the issue. The delay can be anywhere from two seconds to about 15. It just sends dead air before the packet is sent. This obviously ties up the channel and is not good practice.
One thing I did notice seemed to be that DCD was sometimes being triggered WHILE the PTT was active. I would see:
PTT 0 = 1
[0H] VE7WOL-9>TY0SWP,CHURCH,VA7IP-10*,WIDE2-1:`2,]l!8>/
DCD 0 = 1
DCD 0 = 0
PTT 0 = 0
The radio is sending unsquelched discriminator audio to the sound card. The levels are within normal range. I can not hear the transmitted packet in the incoming audio.
My setup is a Raspberry Pi3B+ with a SYBA CM-UAUD USB sound card, running 48000 Hz (native rate). Radio is a Motorola Spectra, modified for headless operation.
Any help or suggestions on the issue are appreciated. Thanks.