diff --git a/src/clock/clock.c b/src/clock/clock.c
index 14c75eae52..33b124e589 100644
--- a/src/clock/clock.c
+++ b/src/clock/clock.c
@@ -589,17 +589,18 @@ vlc_clock_main_t *vlc_clock_main_New(struct vlc_logger *parent_logger, struct vl
 
 void vlc_clock_main_Reset(vlc_clock_main_t *main_clock)
 {
-    vlc_mutex_lock(&main_clock->lock);
+    vlc_mutex_assert(&main_clock->lock);
+
     vlc_clock_main_reset(main_clock);
     main_clock->first_pcr =
         clock_point_Create(VLC_TICK_INVALID, VLC_TICK_INVALID);
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 void vlc_clock_main_SetFirstPcr(vlc_clock_main_t *main_clock,
                                 vlc_tick_t system_now, vlc_tick_t ts)
 {
-    vlc_mutex_lock(&main_clock->lock);
+    vlc_mutex_assert(&main_clock->lock);
+
     if (main_clock->first_pcr.system == VLC_TICK_INVALID)
     {
         main_clock->first_pcr = clock_point_Create(system_now, ts);
@@ -607,29 +608,29 @@ void vlc_clock_main_SetFirstPcr(vlc_clock_main_t *main_clock,
         main_clock->wait_sync_ref =
             clock_point_Create(VLC_TICK_INVALID, VLC_TICK_INVALID);
     }
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 void vlc_clock_main_SetInputDejitter(vlc_clock_main_t *main_clock,
                                      vlc_tick_t delay)
 {
-    vlc_mutex_lock(&main_clock->lock);
+    vlc_mutex_assert(&main_clock->lock);
+
     main_clock->input_dejitter = delay;
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 void vlc_clock_main_SetDejitter(vlc_clock_main_t *main_clock,
                                 vlc_tick_t dejitter)
 {
-    vlc_mutex_lock(&main_clock->lock);
+    vlc_mutex_assert(&main_clock->lock);
+
     main_clock->output_dejitter = dejitter;
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 void vlc_clock_main_ChangePause(vlc_clock_main_t *main_clock, vlc_tick_t now,
                                 bool paused)
 {
-    vlc_mutex_lock(&main_clock->lock);
+    vlc_mutex_assert(&main_clock->lock);
+
     assert(paused == (main_clock->pause_date == VLC_TICK_INVALID));
 
     if (paused)
@@ -653,7 +654,6 @@ void vlc_clock_main_ChangePause(vlc_clock_main_t *main_clock, vlc_tick_t now,
         main_clock->pause_date = VLC_TICK_INVALID;
         vlc_cond_broadcast(&main_clock->cond);
     }
-    vlc_mutex_unlock(&main_clock->lock);
 }
 
 void vlc_clock_main_Delete(vlc_clock_main_t *main_clock)
@@ -668,6 +668,17 @@ void vlc_clock_main_Delete(vlc_clock_main_t *main_clock)
     free(main_clock);
 }
 
+void vlc_clock_main_Lock(vlc_clock_main_t *main_clock)
+{
+    vlc_mutex_lock(&main_clock->lock);
+}
+
+void vlc_clock_main_Unlock(vlc_clock_main_t *main_clock)
+{
+    vlc_mutex_assert(&main_clock->lock);
+    vlc_mutex_unlock(&main_clock->lock);
+}
+
 vlc_tick_t vlc_clock_Update(vlc_clock_t *clock, vlc_tick_t system_now,
                             vlc_tick_t ts, double rate)
 {
@@ -738,12 +749,13 @@ vlc_clock_t *vlc_clock_main_CreateMaster(vlc_clock_main_t *main_clock,
                                          const struct vlc_clock_cbs *cbs,
                                          void *cbs_data)
 {
+    vlc_mutex_assert(&main_clock->lock);
+
     /* The master has always the 0 priority */
     vlc_clock_t *clock = vlc_clock_main_Create(main_clock, track_str_id, 0, cbs, cbs_data);
     if (!clock)
         return NULL;
 
-    vlc_mutex_lock(&main_clock->lock);
     assert(main_clock->master == NULL);
 
     if (main_clock->input_master == NULL)
@@ -753,19 +765,19 @@ vlc_clock_t *vlc_clock_main_CreateMaster(vlc_clock_main_t *main_clock,
 
     main_clock->master = clock;
     main_clock->rc++;
-    vlc_mutex_unlock(&main_clock->lock);
 
     return clock;
 }
 
 vlc_clock_t *vlc_clock_main_CreateInputMaster(vlc_clock_main_t *main_clock)
 {
+    vlc_mutex_assert(&main_clock->lock);
+
     /* The master has always the 0 priority */
     vlc_clock_t *clock = vlc_clock_main_Create(main_clock, "input", 0, NULL, NULL);
     if (!clock)
         return NULL;
 
-    vlc_mutex_lock(&main_clock->lock);
     assert(main_clock->input_master == NULL);
 
     /* Even if the master ES clock has already been created, it should not
@@ -779,7 +791,6 @@ vlc_clock_t *vlc_clock_main_CreateInputMaster(vlc_clock_main_t *main_clock)
     clock->ops = &master_ops;
     main_clock->input_master = clock;
     main_clock->rc++;
-    vlc_mutex_unlock(&main_clock->lock);
 
     return clock;
 }
@@ -790,6 +801,8 @@ vlc_clock_t *vlc_clock_main_CreateSlave(vlc_clock_main_t *main_clock,
                                         const struct vlc_clock_cbs *cbs,
                                         void *cbs_data)
 {
+    vlc_mutex_assert(&main_clock->lock);
+
     /* SPU outputs should have lower priority than VIDEO outputs since they
      * necessarily depend on a VIDEO output. This mean that a SPU reference
      * point will always be overridden by AUDIO or VIDEO outputs. Cf.
@@ -812,10 +825,8 @@ vlc_clock_t *vlc_clock_main_CreateSlave(vlc_clock_main_t *main_clock,
     if (!clock)
         return NULL;
 
-    vlc_mutex_lock(&main_clock->lock);
     clock->ops = &slave_ops;
     main_clock->rc++;
-    vlc_mutex_unlock(&main_clock->lock);
 
     return clock;
 }
diff --git a/src/clock/clock.h b/src/clock/clock.h
index bd48aadfe9..905efa8546 100644
--- a/src/clock/clock.h
+++ b/src/clock/clock.h
@@ -79,16 +79,48 @@ vlc_clock_main_t *vlc_clock_main_New(struct vlc_logger *parent_logger, struct vl
 
 /**
  * Destroy the clock main
+ *
+ * @param main_clock the unlocked main_clock
  */
 void vlc_clock_main_Delete(vlc_clock_main_t *main_clock);
 
+/**
+ * Lock the main_clock mutex
+ *
+ * All vlc_clock_main_t functions must be called with the lock held, except
+ * vlc_clock_main_Delete()
+ *
+ * @param main_clock the unlocked main_clock
+ */
+void vlc_clock_main_Lock(vlc_clock_main_t *main_clock);
+
+/**
+ * Unlock the main_clock mutex
+ *
+ * @param main_clock the locked main_clock
+ */
+void vlc_clock_main_Unlock(vlc_clock_main_t *main_clock);
+
 /**
  * Reset the vlc_clock_main_t
+ *
+ * @param main_clock the locked main_clock
  */
 void vlc_clock_main_Reset(vlc_clock_main_t *main_clock);
 
+/**
+ * Set the first PCR point
+ *
+ * @param main_clock the locked main_clock
+ */
 void vlc_clock_main_SetFirstPcr(vlc_clock_main_t *main_clock,
                                 vlc_tick_t system_now, vlc_tick_t ts);
+
+/**
+ * Set the input dejitter
+ *
+ * @param main_clock the locked main_clock
+ */
 void vlc_clock_main_SetInputDejitter(vlc_clock_main_t *main_clock,
                                      vlc_tick_t delay);
 
@@ -96,12 +128,16 @@ void vlc_clock_main_SetInputDejitter(vlc_clock_main_t *main_clock,
  * This function sets the dejitter delay to absorb the clock jitter
  *
  * Also used as the maximum delay before the synchro is considered to kick in.
+ *
+ * @param main_clock the locked main_clock
  */
 void vlc_clock_main_SetDejitter(vlc_clock_main_t *main_clock, vlc_tick_t dejitter);
 
 
 /**
  * This function allows changing the pause status.
+ *
+ * @param main_clock the locked main_clock
  */
 void vlc_clock_main_ChangePause(vlc_clock_main_t *clock, vlc_tick_t system_now,
                                 bool paused);
@@ -112,6 +148,8 @@ void vlc_clock_main_ChangePause(vlc_clock_main_t *clock, vlc_tick_t system_now,
  * @warning There can be only one master at a given time.
  *
  * You must use vlc_clock_Delete to free it.
+ *
+ * @param main_clock the locked main_clock
  */
 vlc_clock_t *vlc_clock_main_CreateMaster(vlc_clock_main_t *main_clock,
                                          const char *track_str_id,
@@ -127,6 +165,8 @@ vlc_clock_t *vlc_clock_main_CreateMaster(vlc_clock_main_t *main_clock,
  * @warning There can be only one input master at a given time.
  *
  * You must use vlc_clock_Delete to free it.
+ *
+ * @param main_clock the locked main_clock
  */
 vlc_clock_t *vlc_clock_main_CreateInputMaster(vlc_clock_main_t *main_clock);
 
@@ -134,6 +174,8 @@ vlc_clock_t *vlc_clock_main_CreateInputMaster(vlc_clock_main_t *main_clock);
  * This function creates a new slave vlc_clock_t interface
  *
  * You must use vlc_clock_Delete to free it.
+ *
+ * @param main_clock the locked main_clock
  */
 vlc_clock_t *vlc_clock_main_CreateSlave(vlc_clock_main_t *main_clock,
                                         const char *track_str_id,
@@ -145,6 +187,8 @@ vlc_clock_t *vlc_clock_main_CreateSlave(vlc_clock_main_t *main_clock,
  * This function creates a new slave vlc_clock_t interface
  *
  * You must use vlc_clock_Delete to free it.
+ *
+ * @param main_clock the locked main_clock
  */
 vlc_clock_t *vlc_clock_CreateSlave(const vlc_clock_t *clock,
                                    enum es_format_category_e cat);
diff --git a/src/input/es_out.c b/src/input/es_out.c
index cf88b9eac6..1512bfc103 100644
--- a/src/input/es_out.c
+++ b/src/input/es_out.c
@@ -1038,6 +1038,7 @@ static void EsOutDecodersStopBuffering( es_out_t *out, bool b_forced )
 
     input_clock_ChangeSystemOrigin( p_sys->p_pgrm->p_input_clock, true, update );
 
+    vlc_clock_main_Lock(p_sys->p_pgrm->clocks.main);
     /* Resetting the main_clock here will drop all points that were sent during
      * the buffering step. Only points coming from the input_clock are dropped
      * here. Indeed, decoders should not send any output frames while buffering
@@ -1053,6 +1054,7 @@ static void EsOutDecodersStopBuffering( es_out_t *out, bool b_forced )
      * point for the sync point. */
     vlc_clock_main_SetFirstPcr(p_sys->p_pgrm->clocks.main, update,
                                i_stream_start);
+    vlc_clock_main_Unlock(p_sys->p_pgrm->clocks.main);
 
     foreach_es_then_es_slaves(p_es)
     {
@@ -1112,7 +1114,10 @@ static void EsOutProgramChangePause( es_out_t *out, bool b_paused, vlc_tick_t i_
     vlc_list_foreach(pgrm, &p_sys->programs, node)
     {
         input_clock_ChangePause(pgrm->p_input_clock, b_paused, i_date);
+
+        vlc_clock_main_Lock(pgrm->clocks.main);
         vlc_clock_main_ChangePause(pgrm->clocks.main, i_date, b_paused);
+        vlc_clock_main_Unlock(pgrm->clocks.main);
     }
 }
 
@@ -1304,8 +1309,10 @@ static void EsOutProgramHandleClockSource( es_out_t *out, es_out_pgrm_t *p_pgrm
             /* Fall-through */
         case VLC_CLOCK_MASTER_INPUT:
         {
+            vlc_clock_main_Lock(p_sys->p_pgrm->clocks.main);
             p_pgrm->clocks.input =
                 vlc_clock_main_CreateInputMaster(p_pgrm->clocks.main);
+            vlc_clock_main_Unlock(p_sys->p_pgrm->clocks.main);
 
             if (p_pgrm->clocks.input == NULL)
                 break;
@@ -1332,8 +1339,10 @@ static void EsOutProgramHandleClockSource( es_out_t *out, es_out_pgrm_t *p_pgrm
 
     if (p_pgrm->active_clock_source != VLC_CLOCK_MASTER_INPUT)
     {
+        vlc_clock_main_Lock(p_pgrm->clocks.main);
         p_pgrm->clocks.input = vlc_clock_main_CreateSlave(
             p_pgrm->clocks.main, "pcr", UNKNOWN_ES, NULL, NULL);
+        vlc_clock_main_Unlock(p_pgrm->clocks.main);
 
         if (p_pgrm->clocks.input != NULL)
         {
@@ -1508,6 +1517,8 @@ static es_out_pgrm_t *EsOutProgramAdd( es_out_t *out, input_source_t *source, in
     const vlc_tick_t pts_delay = p_sys->i_pts_delay + p_sys->i_pts_jitter
                                + p_sys->i_tracks_pts_delay;
     input_clock_SetJitter( p_pgrm->p_input_clock, pts_delay, p_sys->i_cr_average );
+
+    vlc_clock_main_Lock(p_pgrm->clocks.main);
     vlc_clock_main_SetInputDejitter(p_pgrm->clocks.main, pts_delay );
 
     /* In case of low delay: don't use any output dejitter. This may result on
@@ -1515,6 +1526,7 @@ static es_out_pgrm_t *EsOutProgramAdd( es_out_t *out, input_source_t *source, in
      * than the visual quality if the user chose this option. */
     if (input_priv(p_input)->b_low_delay)
         vlc_clock_main_SetDejitter(p_pgrm->clocks.main, 0);
+    vlc_clock_main_Unlock(p_pgrm->clocks.main);
 
     /* Append it */
     vlc_list_append(&p_pgrm->node, &p_sys->programs);
@@ -2272,6 +2284,7 @@ static void EsOutCreateDecoder( es_out_t *out, es_out_id_t *p_es )
             vlc_assert_unreachable();
     }
 
+    vlc_clock_main_Lock(p_es->p_pgrm->clocks.main);
     if( p_es->fmt.i_cat != UNKNOWN_ES
      && p_es->fmt.i_cat == clock_source_cat
      && p_es->p_pgrm->p_master_es_clock == NULL )
@@ -2290,6 +2303,7 @@ static void EsOutCreateDecoder( es_out_t *out, es_out_id_t *p_es )
                                                    p_es->fmt.i_cat,
                                                    &clock_cbs, p_es);
     }
+    vlc_clock_main_Unlock(p_es->p_pgrm->clocks.main);
 
     if( !p_es->p_clock )
     {
@@ -3929,7 +3943,9 @@ static int EsOutVaPrivControlLocked( es_out_t *out, input_source_t *source,
         {
             input_clock_SetJitter(pgrm->p_input_clock,
                                   i_pts_delay, i_cr_average);
+            vlc_clock_main_Lock(pgrm->clocks.main);
             vlc_clock_main_SetInputDejitter(pgrm->clocks.main, i_pts_delay);
+            vlc_clock_main_Unlock(pgrm->clocks.main);
         }
         return VLC_SUCCESS;
     }
diff --git a/src/stream_output/stream_output.c b/src/stream_output/stream_output.c
index e09f95580b..31a1786d98 100644
--- a/src/stream_output/stream_output.c
+++ b/src/stream_output/stream_output.c
@@ -792,15 +792,21 @@ void sout_ClockMainDelete( vlc_clock_main_t *main_clock )
 
 void sout_ClockMainSetFirstPcr( vlc_clock_main_t *main_clock, vlc_tick_t pcr )
 {
+    vlc_clock_main_Lock( main_clock );
     vlc_clock_main_Reset( main_clock );
     vlc_clock_main_SetFirstPcr( main_clock, vlc_tick_now(), pcr );
+    vlc_clock_main_Unlock( main_clock );
 }
 
 vlc_clock_t *sout_ClockCreate( vlc_clock_main_t *main_clock,
                                const es_format_t *fmt )
 {
-    return vlc_clock_main_CreateSlave( main_clock, NULL, fmt->i_cat,
-                                       NULL, NULL );
+    vlc_clock_main_Lock( main_clock );
+    vlc_clock_t *clock =
+        vlc_clock_main_CreateSlave( main_clock, NULL, fmt->i_cat,
+                                    NULL, NULL );
+    vlc_clock_main_Unlock( main_clock );
+    return clock;
 }
 
 void sout_ClockDelete( vlc_clock_t *clock )