patch proposed by issue 21 revising realtime priority for jack input applied

darkice/trunk/darkice.cfg

@@ -6,6 +6,8 @@
 duration        = 60        # duration of encoding, in seconds. 0 means forever
 bufferSecs      = 5         # size of internal slip buffer, in seconds
 reconnect       = yes       # reconnect to the server(s) if disconnected
+realtime        = yes       # run the encoder with POSIX realtime priority
+rtprio          = 3         # scheduling priority for the realtime threads
 
 # this section describes the audio input that will be streamed
 [input]

darkice/trunk/man/darkice.cfg.5

@@ -62,6 +62,10 @@ streaming, "yes" or "no". (optional parameter, defaults to "yes")
 .I realtime
 Use POSIX realtime scheduling, "yes" or "no".
 (optional parameter, defaults to "yes")
+.TP
+.I rtprio 
+Scheduling priority for the realtime threads.
+(optional parameter, defaults to 4)
 
 
 .PP

darkice/trunk/src/DarkIce.cpp

@@ -164,6 +164,13 @@ DarkIce :: init ( const Config      & config )              throw ( Exception )
     str = cs->get( "realtime" );
     enableRealTime = str ? (Util::strEq( str, "yes") ? true : false) : true;
 
+    // get realtime scheduling priority. If unspecified, set it to 4.
+    // Why 4? jackd's default priority is 10, jackd client threads run
+    // at 5, so make the encoder thread use 4. jackd automatically sets
+    // the process callback priority to the right value, so all we have
+    // to care about is the encoder priority.
+    str = cs->get( "rtprio" );
+    realTimeSchedPriority = (str != NULL) ? Util::strToL( str ) : 4;
 
     // the [input] section
     if ( !(cs = config.get( "input")) ) {
@@ -1111,13 +1118,17 @@ DarkIce :: setRealTimeScheduling ( void )               throw ( Exception )
     }
     origSchedPriority = param.sched_priority;
     
-    /* set SCHED_FIFO with max - 1 priority */
+    /* set SCHED_FIFO with max - 1 priority or user configured value */
     if ( (high_priority = sched_get_priority_max(SCHED_FIFO)) == -1 ) {
         throw Exception(__FILE__,__LINE__,"sched_get_priority_max",errno);
     }
     reportEvent( 8, "scheduler high priority", high_priority);
 
-    param.sched_priority = high_priority - 1;
+    if (realTimeSchedPriority > high_priority) {
+        param.sched_priority = high_priority - 1;
+    } else {
+        param.sched_priority = realTimeSchedPriority;
+    }
 
     if ( sched_setscheduler( 0, SCHED_FIFO, &param) == -1 ) {
         reportEvent( 1,

darkice/trunk/src/DarkIce.h

@@ -124,6 +124,11 @@ class DarkIce : public virtual Referable, public virtual Reporter
          */
         int                     enableRealTime;
 
+        /**
+         *  Scheduling priority for the realtime threads
+         */
+        int                     realTimeSchedPriority;
+
         /**
          *  Original scheduling policy
          */