Dino: bump input latency to 20ms

hosts/by-name/moby/default.nix

@@ -69,7 +69,7 @@
     # - `systemctl --user restart pipewire`
     # - pipewire users will likely stop outputting audio until they are also restarted
     #
-    # there's seemingly two buffers for the mic:
+    # there's seemingly two buffers for the mic (see: <https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/FAQ#pipewire-buffering-explained>)
     # 1. Pipewire buffering out of the driver and into its own member.
     # 2. Pipewire buffering into Dino.
     # the latter is fixed at 10ms by Dino, difficult to override via runtime config.

hosts/common/programs/dino.nix

@@ -51,6 +51,14 @@ in
         Restart = "always";
         RestartSec = "20s";
       };
+
+      # audio buffering; see: <https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/FAQ#pipewire-buffering-explained>
+      # dino defaults to 10ms mic buffer, which causes underruns, which Dino handles *very* poorly
+      # as in, the other end of the call will just not receive sound from us for a couple seconds.
+      # pipewire uses power-of-two buffering for the mic itself. that would put us at 21.33 ms, but this env var supports only whole numbers (21ms ends up not power-of-two).
+      # also, Dino's likely still doing things in 10ms batches internally anyway.
+      environment.PULSE_LATENCY_MSEC = "20";
+
       # note that debug logging during calls produces so much journal spam that it pegs the CPU and causes dropped audio
       # environment.G_MESSAGES_DEBUG = "all";
     };