lavfi/avfilter: fix typos in doxgens

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/avfilter.h

@@ -668,7 +668,7 @@ struct AVFilterContext {
      * allowed threading types. I.e. a threading type needs to be set in both
      * to be allowed.
      *
-     * After the filter is initialzed, libavfilter sets this field to the
+     * After the filter is initialized, libavfilter sets this field to the
      * threading type that is actually used (0 for no multithreading).
      */
     int thread_type;
@@ -830,7 +830,7 @@ struct AVFilterLink {
 
     /**
      * True if the link is closed.
-     * If set, all attemps of start_frame, filter_frame or request_frame
+     * If set, all attempts of start_frame, filter_frame or request_frame
      * will fail with AVERROR_EOF, and if necessary the reference will be
      * destroyed.
      * If request_frame returns AVERROR_EOF, this flag is set on the
@@ -1260,7 +1260,7 @@ AVFilterGraph *avfilter_graph_alloc(void);
  *
  * @return the context of the newly created filter instance (note that it is
  *         also retrievable directly through AVFilterGraph.filters or with
- *         avfilter_graph_get_filter()) on success or NULL or failure.
+ *         avfilter_graph_get_filter()) on success or NULL on failure.
  */
 AVFilterContext *avfilter_graph_alloc_filter(AVFilterGraph *graph,
                                              const AVFilter *filter,
@@ -1384,7 +1384,7 @@ void avfilter_inout_free(AVFilterInOut **inout);
  * outputs of the already existing filters, which are provided as
  * inputs to the parsed filters.
  *
- * @param graph   the filter graph where to link the parsed grap context
+ * @param graph   the filter graph where to link the parsed graph context
  * @param filters string to be parsed
  * @param inputs  linked list to the inputs of the graph
  * @param outputs linked list to the outputs of the graph
@@ -1482,7 +1482,7 @@ int avfilter_graph_send_command(AVFilterGraph *graph, const char *target, const
  *               "all" sends to all filters
  *               otherwise it can be a filter or filter instance name
  *               which will send the command to all matching filters.
- * @param cmd    the command to sent, for handling simplicity all commands must be alphanummeric only
+ * @param cmd    the command to sent, for handling simplicity all commands must be alphanumeric only
  * @param arg    the argument for the command
  * @param ts     time at which the command should be sent to the filter
  *