Index: /trunk/libffado/src/libieee1394/CycleTimerHelper.cpp
===================================================================
--- /trunk/libffado/src/libieee1394/CycleTimerHelper.cpp (revision 764)
+++ /trunk/libffado/src/libieee1394/CycleTimerHelper.cpp (revision 767)
@@ -32,4 +32,20 @@
 #define DLL_COEFF_B   (DLL_SQRT2 * DLL_OMEGA)
 #define DLL_COEFF_C   (DLL_OMEGA * DLL_OMEGA)
+
+/*
+#define ENTER_CRITICAL_SECTION { \
+    if (pthread_mutex_trylock(&m_compute_vars_lock) == EBUSY) { \
+        debugWarning(" (%p) lock clash\n", this); \
+        ENTER_CRITICAL_SECTION; \
+    } \
+    }
+*/
+#define ENTER_CRITICAL_SECTION { \
+    ENTER_CRITICAL_SECTION; \
+    }
+#define EXIT_CRITICAL_SECTION { \
+    EXIT_CRITICAL_SECTION; \
+    }
+
 
 IMPL_DEBUG_MODULE( CycleTimerHelper, CycleTimerHelper, DEBUG_LEVEL_NORMAL );
@@ -168,5 +184,5 @@
 CycleTimerHelper::Execute()
 {
-    debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, "Execute %p...\n", this);
+    debugOutput( DEBUG_LEVEL_VERY_VERBOSE, "Execute %p...\n", this);
     uint32_t cycle_timer;
     uint64_t local_time;
@@ -175,5 +191,5 @@
         return false;
     }
-    debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " read : CTR: %11lu, local: %17llu\n",
+    debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " read : CTR: %11lu, local: %17llu\n",
                     cycle_timer, local_time);
 
@@ -195,5 +211,5 @@
 
         double diff = m_next_time_usecs - m_current_time_usecs;
-        debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " usecs: local: %11llu current: %f next: %f, diff: %f\n",
+        debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " usecs: local: %11llu current: %f next: %f, diff: %f\n",
                     local_time, m_current_time_usecs, m_next_time_usecs, diff);
 
@@ -204,5 +220,5 @@
         m_current_time_usecs = m_next_time_usecs;
         m_next_time_usecs = (local_time - usecs_late) + m_usecs_per_update;
-        debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " usecs: current: %f next: %f usecs_late=%f\n",
+        debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " usecs: current: %f next: %f usecs_late=%f\n",
                     m_current_time_usecs, m_next_time_usecs, usecs_late);
 
@@ -213,8 +229,8 @@
                                      (uint64_t)((DLL_COEFF_B * diff_ticks) + m_dll_e2));
         m_dll_e2 += DLL_COEFF_C * diff_ticks;
-        debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " ticks: current: %f next: %f diff=%f\n",
+        debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " ticks: current: %f next: %f diff=%f\n",
                     m_current_time_ticks, m_next_time_ticks, diff_ticks);
 
-        debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " state: local: %11llu, dll_e2: %f, rate: %f\n",
+        debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " state: local: %11llu, dll_e2: %f, rate: %f\n",
                     local_time, m_dll_e2, getRate());
     }
@@ -224,9 +240,9 @@
 
     // FIXME: priority inversion!
-    pthread_mutex_lock(&m_compute_vars_lock);
+    ENTER_CRITICAL_SECTION;
     m_current_vars.ticks = m_current_time_ticks;
     m_current_vars.usecs = m_current_time_usecs;
     m_current_vars.rate = getRate();
-    pthread_mutex_unlock(&m_compute_vars_lock);
+    EXIT_CRITICAL_SECTION;
 
     // wait for the next update period
@@ -235,5 +251,5 @@
     //int64_t time_to_sleep = m_usecs_per_update;
     if (time_to_sleep > 0) {
-        debugOutput( DEBUG_LEVEL_ULTRA_VERBOSE, " sleeping %lld usecs (avg delay: %f)\n", time_to_sleep, m_avg_wakeup_delay);
+        debugOutput( DEBUG_LEVEL_VERY_VERBOSE, " sleeping %lld usecs (avg delay: %f)\n", time_to_sleep, m_avg_wakeup_delay);
         usleep(time_to_sleep);
     }
@@ -255,7 +271,7 @@
 
     // reduce lock contention
-    pthread_mutex_lock(&m_compute_vars_lock);
+    ENTER_CRITICAL_SECTION;
     my_vars = m_current_vars;
-    pthread_mutex_unlock(&m_compute_vars_lock);
+    EXIT_CRITICAL_SECTION;
 
     double time_diff = now - my_vars.usecs;
@@ -266,9 +282,12 @@
     if (y_step_in_ticks_int > 0) {
         retval = addTicks(offset_in_ticks_int, y_step_in_ticks_int);
+        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "y_step_in_ticks_int > 0: %lld, time_diff: %f, rate: %f, retval: %lu\n", 
+                     y_step_in_ticks_int, time_diff, my_vars.rate, retval);
     } else {
+        retval = substractTicks(offset_in_ticks_int, -y_step_in_ticks_int);
+
         // this can happen if the update thread was woken up earlier than it should have been
-        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "y_step_in_ticks_int <= 0: %lld, time_diff: %f, rate: %f\n", 
-                     y_step_in_ticks_int, time_diff, my_vars.rate);
-        retval = substractTicks(offset_in_ticks_int, -y_step_in_ticks_int);
+        debugOutput(DEBUG_LEVEL_VERY_VERBOSE, "y_step_in_ticks_int <= 0: %lld, time_diff: %f, rate: %f, retval: %lu\n", 
+                     y_step_in_ticks_int, time_diff, my_vars.rate, retval);
     }
 
Index: /trunk/libffado/src/libieee1394/IsoHandlerManager.cpp
===================================================================
--- /trunk/libffado/src/libieee1394/IsoHandlerManager.cpp (revision 759)
+++ /trunk/libffado/src/libieee1394/IsoHandlerManager.cpp (revision 767)
@@ -356,5 +356,5 @@
         if(irq_interval <= 0) irq_interval=1;
         // FIXME: test
-        //irq_interval=1;
+        irq_interval=1;
 
 #else
@@ -440,5 +440,5 @@
             debugError("Max packet size too large! (%d)\n", stream->getMaxPacketSize());
         }
-
+        irq_interval=2;
 #endif
         // the SP specifies how many packets to buffer
Index: /trunk/libffado/src/libieee1394/IsoHandlerManager.h
===================================================================
--- /trunk/libffado/src/libieee1394/IsoHandlerManager.h (revision 760)
+++ /trunk/libffado/src/libieee1394/IsoHandlerManager.h (revision 767)
@@ -34,5 +34,5 @@
 #include <vector>
 
-//#define THREAD_PER_ISOHANDLER
+// #define THREAD_PER_ISOHANDLER
 
 #define FFADO_MAX_ISO_HANDLERS_PER_PORT 16