v2.33.87 — Remote rtl_tcp decoding and squelch

Added

• Remote rtl_tcp support for Pager, DSC, APRS and Morse. Stock rtl_fm can't connect to rtl_tcp, so these modes couldn't use a networked RTL-SDR. Remote devices now stream IQ through a small built-in rtl_tcp client into the csdr demodulator (FM, AM and SSB). Direct sampling is never enabled on an R828D (RTL-SDR Blog V4). (#410)

Fixed

• No squelch on HackRF or remote rtl_tcp audio. The csdr pipeline ignored the squelch setting, so the listening post hissed between transmissions. The channel is now gated on its power (squelch 0-100 maps to -80 to -10 dB). (#410)
• Quick mode switches on a remote rtl_tcp server failed with "busy with another client". rtl_tcp can take several seconds to release the previous client; the client now waits long enough. (#410)
• Pager and DSC reported "started" when rtl_fm exited immediately. They now return rtl_fm's error, with a hint when the device is a remote rtl_tcp server. (#410)
• Meters ignored the remote rtl_tcp server setting and always used local device 0. A remote server is now passed straight to rtlamr, and the local rtl_tcp that rtlamr uses listens on 127.0.0.1 only instead of every interface. (#410)