vlc_filter: move documentation and fix doxygen warnings

include/vlc_filter.h:371: warning: The following parameters of filter_AddProxyCallbacks(vlc_object_t *obj, filter_t *filter, vlc_callback_t restart_cb) are not documented:
      parameter 'obj'
      parameter 'filter'

    include/vlc_filter.h:527: warning: The following parameter of filter_chain_AppendFilter(filter_chain_t *chain, const char *name, const config_chain_t *cfg, const es_format_t *fmt_out) is not documented:
      parameter 'cfg'

    include/vlc_filter.h:471: warning: argument 'psz_capability' of command @param is not found in the argument list of filter_chain_NewSPU(vlc_object_t *obj, const char *cap)

    include/vlc_filter.h:471: warning: The following parameter of filter_chain_NewSPU(vlc_object_t *obj, const char *cap) is not documented:
      parameter 'cap'

    include/vlc_filter.h:506: warning: Found unknown command '\paramt'

    include/vlc_filter.h:504: warning: The following parameter of filter_chain_Reset(filter_chain_t *p_chain, const es_format_t *p_fmt_in, vlc_video_context *vctx_in, const es_format_t *p_fmt_out) is not documented:
      parameter 'vctx_in'

    include/vlc_filter.h:608: warning: The following parameter of filter_chain_SubSource(filter_chain_t *chain, spu_t *spu, vlc_tick_t display_date) is not documented:
      parameter 'spu'

    include/vlc_filter.h:383: warning: The following parameters of filter_DelProxyCallbacks(vlc_object_t *obj, filter_t *filter, vlc_callback_t restart_cb) are not documented:
      parameter 'obj'
      parameter 'filter'

include/vlc_filter.h

@@ -367,6 +367,8 @@ static inline int filter_GetInputAttachments( filter_t *p_filter,
  * This function duplicates every variables from the filter, and adds a proxy
  * callback to trigger filter events from obj.
  *
+ * \param obj the object to add the callback proxy to
+ * \param filter the filter object for which the callback will be proxified
  * \param restart_cb a vlc_callback_t to call if the event means restarting the
  * filter (i.e. an event on a non-command variable)
  */
@@ -379,6 +381,8 @@ VLC_API void filter_AddProxyCallbacks( vlc_object_t *obj, filter_t *filter,
  * This function removes the callbacks previously added to every duplicated
  * variables, and removes them afterward.
  *
+ * \param obj the object to remove the callback proxy from
+ * \param filter the filter object for which the callback was proxified
  * \param restart_cb the same vlc_callback_t passed to filter_AddProxyCallbacks
  */
 VLC_API void filter_DelProxyCallbacks( vlc_object_t *obj, filter_t *filter,
@@ -473,7 +477,7 @@ typedef struct filter_chain_t filter_chain_t;
  * \param psz_capability vlc capability of filters in filter chain
  * \return pointer to a filter chain
  */
-filter_chain_t * filter_chain_NewSPU( vlc_object_t *obj, const char *psz_capability )
+filter_chain_t * filter_chain_NewSPU(vlc_object_t *obj, const char *psz_capability)
 VLC_USED;
 #define filter_chain_NewSPU( a, b ) filter_chain_NewSPU( VLC_OBJECT( a ), b )
 
@@ -495,9 +499,9 @@ VLC_USED;
  * Delete filter chain will delete all filters in the chain and free all
  * allocated data. The pointer to the filter chain is then no longer valid.
  *
- * \param p_chain pointer to filter chain
+ * \param chain pointer to filter chain
  */
-VLC_API void filter_chain_Delete( filter_chain_t * );
+VLC_API void filter_chain_Delete(filter_chain_t *chain);
 
 /**
  * Reset filter chain will delete all filters in the chain and
@@ -505,7 +509,7 @@ VLC_API void filter_chain_Delete( filter_chain_t * );
  *
  * \param p_chain pointer to filter chain
  * \param p_fmt_in new fmt_in params
- * \paramt vctx_in new input video context
+ * \param vctx_in new input video context
  * \param p_fmt_out new fmt_out params
  */
 VLC_API void filter_chain_Reset( filter_chain_t *p_chain,
@@ -525,6 +529,7 @@ VLC_API void filter_chain_Clear(filter_chain_t *);
  *
  * \param chain filter chain to append a filter to
  * \param name filter name
+ * \param cfg the configuration chain for the filter
  * \param fmt_out filter output format
  * \return a pointer to the filter or NULL on error
  */
@@ -604,9 +609,10 @@ VLC_API void filter_chain_VideoFlush( filter_chain_t * );
  * Generate subpictures from a chain of subpicture source "filters".
  *
  * \param chain filter chain
+ * \param spu an initialized subpicture unit
  * \param display_date of subpictures
  */
-void filter_chain_SubSource(filter_chain_t *chain, spu_t *,
+void filter_chain_SubSource(filter_chain_t *chain, spu_t *spu,
                             vlc_tick_t display_date);
 
 /**

src/misc/filter_chain.c

@@ -88,9 +88,6 @@ static filter_chain_t *filter_chain_NewInner( vlc_object_t *obj,
 }
 
 #undef filter_chain_NewSPU
-/**
- * Filter chain initialisation
- */
 filter_chain_t *filter_chain_NewSPU( vlc_object_t *obj, const char *cap )
 {
     return filter_chain_NewInner( obj, cap, NULL, false, SPU_ES );
@@ -169,9 +166,6 @@ void filter_chain_Clear( filter_chain_t *p_chain )
         filter_chain_DeleteFilter( p_chain, &p_chain->first->filter );
 }
 
-/**
- * Filter chain destruction
- */
 void filter_chain_Delete( filter_chain_t *p_chain )
 {
     filter_chain_Clear( p_chain );