fix hd-rum-transcode crash

since recent rewrite (17th Mar, commit 4def13b, pushed to master on Fri),
simple:
`hd-rumtranscode 8M 5004` crashed with:
`Invalid bitrate value -3 passed (either positive bitrate or magic values from -2 supported)!`

because RATE_DEFAULT is dispatched in main but not otherwise.

In the different contexts, RATE_DEFAULT is invalid so it must not be the
default init in VRXTX_INIT initializer.

Author: MartinPulec

src/host.h

@@ -119,7 +119,6 @@ void set_audio_delay(int val);
 #define RATE_AUTO                   (-1) ///< spread packets evenly across frame time (currently 3/4)
 #define RATE_DYNAMIC                (-2) ///< same as @ref RATE_AUTO but occasional excess frame allowed
 #define RATE_MIN                RATE_DYNAMIC
-#define RATE_DEFAULT                (-3) ///< imaginary value, must not be passed to transmit module
 #define RATE_FLAG_FIXED_RATE (1ll<<62ll) ///< use the bitrate as fixed, not capped
 
 struct init_data;

src/main.cpp

@@ -127,6 +127,8 @@ constexpr char MOD_NAME[] = "[main] ";
 
 constexpr char DEFAULT_AUDIO_CODEC[]       = "PCM";
 constexpr int  PORT_BASE                   = 5004;
+#define RATE_DEFAULT \
+        (-3) ///< imaginary value, must not be passed to transmit module
 
 constexpr int OPT_AUDIO_CAPTURE_CHANNELS = ('a' << 8) | 'c';
 constexpr int OPT_AUDIO_DELAY            = ('A' << 8) | 'D';

src/video_rxtx.hpp

@@ -86,7 +86,7 @@ struct vrxtx_params {
                 .rx_port        = -1, \
                 .tx_port        = -1, \
                 .fec            = "none", \
-                .bitrate        = RATE_DEFAULT, \
+                .bitrate        = RATE_UNLIMITED, \
                 .decoder_mode   = VIDEO_NORMAL, \
                 .protocol_opts  = "", \
                 .start_time     = 0, \