diff --git a/src/lib/condition.c b/src/lib/condition.c
index 0d731f959..dfc79c7c5 100644
--- a/src/lib/condition.c
+++ b/src/lib/condition.c
@@ -21,6 +21,15 @@
 
 #include "lib/condition.h"
 
+/**
+ * @file Condition variables
+ */
+
+/**
+ * Initialize a condition variable
+ * @param self is a pointer to the condition variable to be initialized
+ * @return self as given
+ */
 CinelerraCondition
 cinelerra_condition_init (CinelerraCondition self)
 {
@@ -32,6 +41,12 @@ cinelerra_condition_init (CinelerraCondition self)
   return self;
 }
 
+
+/**
+ * Destroy a condition variable
+ * @param self is a pointer to the condition variable to be destroyed
+ * @return self as given
+ */
 CinelerraCondition
 cinelerra_condition_destroy (CinelerraCondition self)
 {
diff --git a/src/lib/condition.h b/src/lib/condition.h
index a34ce45ff..7925fd993 100644
--- a/src/lib/condition.h
+++ b/src/lib/condition.h
@@ -24,6 +24,10 @@
 
 #include "lib/locking.h"
 
+/**
+ * @file Condition variables, header
+ */
+
 
 /**
  * Condition variables.
@@ -38,20 +42,10 @@ typedef struct cinelerra_condition_struct cinelerra_condition;
 typedef cinelerra_condition* CinelerraCondition;
 
 
-/**
- * Initialize a condition variable
- * @param self is a pointer to the condition variable to be initialized
- * @return self as given
- */
 CinelerraCondition
 cinelerra_condition_init (CinelerraCondition self);
 
 
-/**
- * Destroy a condition variable
- * @param self is a pointer to the condition variable to be destroyed
- * @return self as given
- */
 CinelerraCondition
 cinelerra_condition_destroy (CinelerraCondition self);
 
diff --git a/src/lib/error.c b/src/lib/error.c
index a5268a07f..d5ea88f01 100644
--- a/src/lib/error.c
+++ b/src/lib/error.c
@@ -23,6 +23,11 @@
 
 #include "lib/error.h"
 
+/**
+ * @file C Error handling in Cinelerra.
+ */
+
+
 /*
   predefined errors
 */
@@ -39,6 +44,13 @@ cinelerra_error_tls_init (void)
   pthread_key_create (&cinelerra_error_tls, NULL);
 }
 
+/**
+ * Set error state for the current thread.
+ * If the error state of the current thread was cleared, then set it, else preserve the old state.
+ * @param nerr name of the error with 'CINELERRA_ERROR_' prefix (example: CINELERRA_ERROR_NO_MEMORY)
+ * @return old state, that is NULL for success, when the state was cleared and a pointer to a pending 
+ * error when the error state was already set
+ */
 const char*
 cinelerra_error_set (const char * nerr)
 {
@@ -52,6 +64,12 @@ cinelerra_error_set (const char * nerr)
 }
 
 
+/**
+ * Get and clear current error state.
+ * This function clears the error state, if it needs to be reused, one has to store it in a temporary
+ * variable.
+ * @return pointer to any pending error of this thread, NULL if no error is pending
+ */
 const char*
 cinelerra_error ()
 {
diff --git a/src/lib/error.h b/src/lib/error.h
index 071a3c914..2b5051652 100644
--- a/src/lib/error.h
+++ b/src/lib/error.h
@@ -31,7 +31,7 @@ extern "C" {
 #include <stdlib.h>
 
 /**
- * C Error handling in Cinelerra.
+ * @file C Error handling in Cinelerra, header.
  */
 
 
@@ -67,20 +67,9 @@ const char* CINELERRA_ERROR_##err = "CINELERRA_ERROR_" #err ":" msg
 (({ERROR (flag, "%s", strchr(CINELERRA_ERROR_##err, ':')+1);}), \
 cinelerra_error_set(CINELERRA_ERROR_##err))
 
-/**
- * Set error state for the current thread.
- * If the error state of the current thread was cleared, then set it, else preserve the old state.
- * @param err name of the error with 'CINELERRA_ERROR_' prefix (example: CINELERRA_ERROR_NO_MEMORY)
- * @return old state, that is NULL for success, when the state was cleared and a pointer to a pending error when the error state was already set
- */
 const char*
 cinelerra_error_set (const char * err);
 
-/**
- * Get and clear current error state.
- * This function clears the error state, if it needs to be reused, one has to store it in a temporary variable.
- * @return pointer to any pending error of this thread, NULL if no error is pending
- */
 const char*
 cinelerra_error ();
 
diff --git a/src/lib/framerate.c b/src/lib/framerate.c
index 138a338a3..b70121a37 100644
--- a/src/lib/framerate.c
+++ b/src/lib/framerate.c
@@ -21,5 +21,10 @@
 
 #include "lib/error.h"
 
+/**
+ * @file Framerate calculations.
+ */
+
+
 CINELERRA_ERROR_DEFINE(FRAMERATE_ILLEGAL_TIME, "invalid time given");
 CINELERRA_ERROR_DEFINE(FRAMERATE_ILLEGAL_FRAME, "invalid frame given");
diff --git a/src/lib/framerate.h b/src/lib/framerate.h
index 2df5971fb..1e862ed0d 100644
--- a/src/lib/framerate.h
+++ b/src/lib/framerate.h
@@ -27,6 +27,11 @@
 #include "lib/error.h"
 #include "lib/time.h"
 
+/**
+ * @file Framerate calculations, header.
+ */
+
+
 /**
  * framerates are defined as a rational number
  * for example NTSC with 30000/1001fps
diff --git a/src/lib/locking.h b/src/lib/locking.h
index fce854b0d..6e53fee97 100644
--- a/src/lib/locking.h
+++ b/src/lib/locking.h
@@ -28,6 +28,10 @@
 
 #include "lib/error.h"
 
+/**
+ * @file Shared declarations for all locking primitives.
+ */
+
 /**
  * used to store the current lock state.
  *
diff --git a/src/lib/mutex.c b/src/lib/mutex.c
index be36f58d2..1425fdd02 100644
--- a/src/lib/mutex.c
+++ b/src/lib/mutex.c
@@ -21,6 +21,16 @@
 
 #include "lib/mutex.h"
 
+/**
+ * @file Mutual exclusion locking.
+ */
+
+
+/**
+ * Initialize a mutex variable
+ * @param self is a pointer to the mutex to be initialized
+ * @return self as given
+ */
 CinelerraMutex
 cinelerra_mutex_init (CinelerraMutex self)
 {
@@ -31,6 +41,11 @@ cinelerra_mutex_init (CinelerraMutex self)
   return self;
 }
 
+/**
+ * Destroy a mutex variable
+ * @param self is a pointer to the mutex to be destroyed
+ * @return self as given
+ */
 CinelerraMutex
 cinelerra_mutex_destroy (CinelerraMutex self)
 {
diff --git a/src/lib/mutex.h b/src/lib/mutex.h
index d9a26ef61..a359d9b75 100644
--- a/src/lib/mutex.h
+++ b/src/lib/mutex.h
@@ -24,6 +24,11 @@
 
 #include "lib/locking.h"
 
+/**
+ * @file Mutual exclusion locking, header.
+ */
+
+
 /**
  * Mutex.
  *
@@ -36,20 +41,10 @@ typedef struct cinelerra_mutex_struct cinelerra_mutex;
 typedef cinelerra_mutex* CinelerraMutex;
 
 
-/**
- * Initialize a mutex variable
- * @param self is a pointer to the mutex to be initialized
- * @return self as given
- */
 CinelerraMutex
 cinelerra_mutex_init (CinelerraMutex self);
 
 
-/**
- * Destroy a mutex variable
- * @param self is a pointer to the mutex to be destroyed
- * @return self as given
- */
 CinelerraMutex
 cinelerra_mutex_destroy (CinelerraMutex self);
 
diff --git a/src/lib/plugin.c b/src/lib/plugin.c
index 4005bb204..184b0cb06 100644
--- a/src/lib/plugin.c
+++ b/src/lib/plugin.c
@@ -28,6 +28,11 @@
 
 #include "plugin.h"
 
+/**
+ * @file Plugin loader.
+ */
+
+
 /* TODO should be set by the build system to the actual plugin path */
 #define CINELERRA_PLUGIN_PATH "~/.cinelerra3/plugins:/usr/local/lib/cinelerra3/plugins:.libs"
 
@@ -93,19 +98,34 @@ void* cinelerra_plugin_registry = NULL;
 /* plugin operations are protected by one big mutex */
 pthread_mutex_t cinelerra_plugin_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-/* the compare function for the registry tree */
+/**
+ * the compare function for the registry tree.
+ * Compares the names of two struct cinelerra_plugin.
+ * @return 0 if a and b are equal, just like strcmp. */
 static int
 cinelerra_plugin_name_cmp (const void* a, const void* b)
 {
   return strcmp (((struct cinelerra_plugin*) a)->name, ((struct cinelerra_plugin*) b)->name);
 }
 
+/**
+ * Initialize the plugin system.
+ * always succeeds or aborts
+ */
 void
 cinelerra_init_plugin (void)
 {
   NOBUG_INIT_FLAG (cinelerra_plugin);
 }
 
+/**
+ * Find and set pathname for the plugin.
+ * Searches through given path for given plugin, trying to find the file's location in the filesystem.
+ * If found, self->pathname will be set to the found plugin file.
+ * @param self The cinelerra_plugin to open look for.
+ * @param path The path to search trough (paths seperated by ":")
+ * @return 0 on success. -1 on error, or if plugin not found in path.
+ */
 int
 cinelerra_plugin_lookup (struct cinelerra_plugin* self, const char* path)
 {
@@ -149,6 +169,18 @@ cinelerra_plugin_lookup (struct cinelerra_plugin* self, const char* path)
   return -1; /* plugin not found */
 }
 
+
+/**
+ * Make an interface available.
+ * To use an interface provided by a plugin it must be opened first. It is allowed to open an interface 
+ * more than once. Each open must be paired with a close.
+ * @param name name of the plugin to use.
+ * @param interface name of the interface to open.
+ * @param min_revision the size of the interface structure is used as measure of a minimal required 
+ * revision (new functions are appended at the end)
+ * @return handle to the interface or NULL in case of a error. The application shall cast this handle to
+ * the actual interface type.
+ */
 struct cinelerra_interface*
 cinelerra_interface_open (const char* name, const char* interface, size_t min_revision)
 {
@@ -277,6 +309,11 @@ cinelerra_interface_open (const char* name, const char* interface, size_t min_re
   return NULL;
 }
 
+/**
+ * Close an interface. Does not free associated resources
+ * Calling this function with self==NULL is legal. Every interface handle must be closed only once.
+ * @param ptr interface to be closed
+ */
 void
 cinelerra_interface_close (void* ptr)
 {
diff --git a/src/lib/plugin.h b/src/lib/plugin.h
index b787870d2..a31e69199 100644
--- a/src/lib/plugin.h
+++ b/src/lib/plugin.h
@@ -32,6 +32,11 @@ extern "C" {
 
 #include "error.h"
 
+/**
+ * @file Plugin loader, header.
+ */
+
+
 NOBUG_DECLARE_FLAG (cinelerra_plugin);
 
 /* tool macros*/
@@ -90,32 +95,14 @@ struct cinelerra_interface
   int (*close)(void);
 };
 
-/**
- * Initialize the plugin system.
- * always succeeds or aborts
- */
 void
 cinelerra_init_plugin (void);
 
 
-/**
- * Make an interface available.
- * To use an interface provided by a plugin it must be opened first. It is allowed to open an interface more than once.
- * Each open must be paired with a close.
- * @param plugin name of the plugin to use.
- * @param name name of the interface to open.
- * @param min_revision the size of the interface structure is used as measure of a minimal required revision (new functions are appended at the end)
- * @return handle to the interface or NULL in case of a error. The application shall cast this handle to the actual interface type.
- */
 struct cinelerra_interface*
 cinelerra_interface_open (const char* plugin, const char* name, size_t min_revision);
 
 
-/**
- * Close an interface. Does not free associated resources
- * Calling this function with self==NULL is legal. Every interface handle must be closed only once.
- * @param self interface to be closed
- */
 void
 cinelerra_interface_close (void* self);
 
diff --git a/src/lib/references.h b/src/lib/references.h
index dd5988ec7..5f5543787 100644
--- a/src/lib/references.h
+++ b/src/lib/references.h
@@ -24,6 +24,11 @@
 
 #include <nobug.h>
 
+/**
+ * @file Strong and Weak references, header.
+ */
+
+
 typedef struct cinelerra_reference_struct cinelerra_reference;
 typedef cinelerra_reference* CinelerraReference;
 
diff --git a/src/lib/rwlock.c b/src/lib/rwlock.c
index 018c69f63..48becb14d 100644
--- a/src/lib/rwlock.c
+++ b/src/lib/rwlock.c
@@ -26,7 +26,16 @@
 CINELERRA_ERROR_DEFINE(RWLOCK_AGAIN, "maximum number of readlocks exceed");
 CINELERRA_ERROR_DEFINE(RWLOCK_DEADLOCK, "deadlock detected");
 
+/**
+ * @file Read/write locks.
+ */
 
+
+/**
+ * Initialize a rwlock
+ * @param self is a pointer to the rwlock to be initialized
+ * @return self as given
+ */
 CinelerraRWLock
 cinelerra_rwlock_init (CinelerraRWLock self)
 {
@@ -37,6 +46,11 @@ cinelerra_rwlock_init (CinelerraRWLock self)
   return self;
 }
 
+/**
+ * destroy a rwlock
+ * @param self is a pointer to the rwlock to be initialized
+ * @return self on success or NULL at error
+ */
 CinelerraRWLock
 cinelerra_rwlock_destroy (CinelerraRWLock self)
 {
@@ -51,6 +65,13 @@ cinelerra_rwlock_destroy (CinelerraRWLock self)
 
 
 
+/**
+ * initialize a rwlockacquirer state
+ * @param self rwlockacquirer to be initialized, must be an automatic variable
+ * @param rwlock associated rwlock
+ * @param state initial state of the mutex, either CINELERRA_RDLOCKED, CINELERRA_WRLOCKED or CINELERRA_UNLOCKED
+ * @return self as given or NULL on error
+ */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_init (CinelerraRWLockacquirer self, CinelerraRWLock rwlock, enum cinelerra_lockstate state)
 {
@@ -94,6 +115,12 @@ cinelerra_rwlockacquirer_init (CinelerraRWLockacquirer self, CinelerraRWLock rwl
 }
 
 
+/**
+ * readlock the rwlock.
+ * must not already be locked
+ * @param self rwlockacquirer associated with a rwlock
+ * @return self as given or NULL on error
+ */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_rdlock (CinelerraRWLockacquirer self)
 {
@@ -119,6 +146,12 @@ cinelerra_rwlockacquirer_rdlock (CinelerraRWLockacquirer self)
 }
 
 
+/**
+ * writelock the rwlock.
+ * must not already be locked
+ * @param self rwlockacquirer associated with a rwlock
+ * @return self as given or NULL on error
+ */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_wrlock (CinelerraRWLockacquirer self)
 {
diff --git a/src/lib/rwlock.h b/src/lib/rwlock.h
index 9bc07f9f3..21ad1e054 100644
--- a/src/lib/rwlock.h
+++ b/src/lib/rwlock.h
@@ -34,6 +34,10 @@
 CINELERRA_ERROR_DECLARE(RWLOCK_AGAIN);
 CINELERRA_ERROR_DECLARE(RWLOCK_DEADLOCK);
 
+/**
+ * @file Read/write locks, header.
+ */
+
 
 /**
  * RWLock.
@@ -47,20 +51,10 @@ typedef struct cinelerra_rwlock_struct cinelerra_rwlock;
 typedef cinelerra_rwlock* CinelerraRWLock;
 
 
-/**
- * Initialize a rwlock
- * @param self is a pointer to the rwlock to be initialized
- * @return self as given
- */
 CinelerraRWLock
 cinelerra_rwlock_init (CinelerraRWLock self);
 
 
-/**
- * destroy a rwlock
- * @param self is a pointer to the rwlock to be initialized
- * @return self on success or NULL at error
- */
 CinelerraRWLock
 cinelerra_rwlock_destroy (CinelerraRWLock self);
 
@@ -90,32 +84,13 @@ cinelerra_rwlockacquirer_ensureunlocked (CinelerraRWLockacquirer self)
 cinelerra_rwlockacquirer NOBUG_CLEANUP(cinelerra_rwlockacquirer_ensureunlocked)
 
 
-/**
- * initialize a rwlockacquirer state
- * @param self rwlockacquirer to be initialized, must be an automatic variable
- * @param cond associated rwlock
- * @param state initial state of the mutex, either CINELERRA_RDLOCKED, CINELERRA_WRLOCKED or CINELERRA_UNLOCKED
- * @return self as given or NULL on error
- */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_init (CinelerraRWLockacquirer self, CinelerraRWLock rwlock, enum cinelerra_lockstate state);
 
-/**
- * readlock the rwlock.
- * must not already be locked
- * @param self rwlockacquirer associated with a rwlock
- * @return self as given or NULL on error
- */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_rdlock (CinelerraRWLockacquirer self);
 
 
-/**
- * writelock the rwlock.
- * must not already be locked
- * @param self rwlockacquirer associated with a rwlock
- * @return self as given or NULL on error
- */
 CinelerraRWLockacquirer
 cinelerra_rwlockacquirer_wrlock (CinelerraRWLockacquirer self);
 
diff --git a/src/lib/time.h b/src/lib/time.h
index a2dea483b..4203ece49 100644
--- a/src/lib/time.h
+++ b/src/lib/time.h
@@ -29,10 +29,15 @@
 #include "lib/error.h"
 
 /*
+ * @file Time calculations.
   this time functions are small macro like wrapers, they are all inlined for performance reasons
-  time is passed around as pointers, this pointer must never be NULL
+  time is passed around as pointers, this pointer must never be NULL.
 
-  timehandling is a delicate business, be careful of precision errors accumulating, TODO explain how to use time
+  timehandling is a delicate business, be careful of precision errors accumulating
+
+  cinelerra_time is starting from zero, never becomes negative.
+  
+  TODO explain how to use time
 
 */
 
@@ -67,6 +72,8 @@ cinelerra_time_normalize (CinelerraTime time)
 
 /**
  * set a time value to zero.
+ * @param time Time to clear
+ * @return time as given
  */
 static inline CinelerraTime
 cinelerra_time_clear (CinelerraTime time)
@@ -81,6 +88,8 @@ cinelerra_time_clear (CinelerraTime time)
 
 /**
  * get current time.
+ * @param time Time to put current time into.
+ * @return time as given
  */
 static inline CinelerraTime
 cinelerra_time_current (CinelerraTime time)
@@ -96,6 +105,10 @@ cinelerra_time_current (CinelerraTime time)
 
 /**
  * init from floating point representation.
+ * @param time The time to be set
+ * @param fp Time in double
+ * @return time as given upon success, NULL if double time given was negative or given time didn't point
+ * anywhere
  */
 static inline CinelerraTime
 cinelerra_time_set_double (CinelerraTime time, double fp)
@@ -120,6 +133,10 @@ cinelerra_time_set_double (CinelerraTime time, double fp)
 
 /**
  * initialize with seconds and microseconds.
+ * @param time Time to set
+ * @param sec Seconds to set
+ * @param usec Microseconds to set
+ * @param Time as given
  */
 static inline CinelerraTime
 cinelerra_time_init (CinelerraTime time, time_t sec, suseconds_t usec)
@@ -135,6 +152,8 @@ cinelerra_time_init (CinelerraTime time, time_t sec, suseconds_t usec)
 
 /**
  * get the seconds part from a time.
+ * @param time Time to get seconds from
+ * @return Seconds elapsed, -1 on error
  */
 static inline time_t
 cinelerra_time_sec (CinelerraTime time)
@@ -147,6 +166,8 @@ cinelerra_time_sec (CinelerraTime time)
 
 /**
  * get the microseconds part of a time.
+ * @param time Time to get microseconds from
+ * @return Microseconds elapsed, -1 on error
  */
 static inline suseconds_t
 cinelerra_time_usec (CinelerraTime time)
@@ -159,6 +180,8 @@ cinelerra_time_usec (CinelerraTime time)
 
 /**
  * convert to floating point repesentation.
+ * @param time Time to get floating point representation from
+ * @return Floating point representation of time. NAN on error.
  */
 static inline double
 cinelerra_time_double_get (CinelerraTime time)
@@ -177,6 +200,9 @@ cinelerra_time_double_get (CinelerraTime time)
 
 /**
  * copy time
+ * @param dest Time-pointer to copy to
+ * @param src Time-source to copy from
+ * @return dest as given
  */
 static inline CinelerraTime
 cinelerra_time_copy (CinelerraTime dest, const CinelerraTime src)
@@ -191,6 +217,9 @@ cinelerra_time_copy (CinelerraTime dest, const CinelerraTime src)
 
 /**
  * add time.
+ * @param dest The result of the add
+ * @param src Time to add to dest
+ * @return dest as given, or NULL on overflow.
  */
 static inline CinelerraTime
 cinelerra_time_add (CinelerraTime dest, const CinelerraTime src)
@@ -215,6 +244,9 @@ cinelerra_time_add (CinelerraTime dest, const CinelerraTime src)
 
 /**
  * substact time.
+ * @param dest The result of subtract
+ * @param src Time to subtract from dest
+ * @return dest as given, or NULL on underflow.
  */
 static inline CinelerraTime
 cinelerra_time_sub (CinelerraTime dest, const CinelerraTime src)