lavfi: replace avfilter_open() with avfilter_graph_alloc_filter().

Since we do not support "standalone" filters not attached to an
AVFilterGraph, we should not have a public function to create such
filters. In addition that function is horribly named, the action it does
cannot be possibly described as "opening" a filter.

doc/APIchanges

@@ -16,6 +16,7 @@ API changes, most recent first:
 2013-xx-xx - lavfi 3.8.0
   Move all content from avfiltergraph.h to avfilter.h. Deprecate
   avfilterhraph.h, user applications should include just avfilter.h
+  Add avfilter_graph_alloc_filter(), deprecate avfilter_open().
 
 2013-xx-xx - lavfi 3.7.0 - avfilter.h
   Add AVFilter.priv_class for exporting filter options through the AVOptions API

libavfilter/avfilter.c

@@ -352,17 +352,16 @@ static const AVClass avfilter_class = {
     .child_class_next = filter_child_class_next,
 };
 
-int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name)
+AVFilterContext *ff_filter_alloc(const AVFilter *filter, const char *inst_name)
 {
     AVFilterContext *ret;
-    *filter_ctx = NULL;
 
     if (!filter)
-        return AVERROR(EINVAL);
+        return NULL;
 
     ret = av_mallocz(sizeof(AVFilterContext));
     if (!ret)
-        return AVERROR(ENOMEM);
+        return NULL;
 
     ret->av_class = &avfilter_class;
     ret->filter   = filter;
@@ -404,8 +403,7 @@ int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *in
     ret->input_count  = ret->nb_inputs;
 #endif
 
-    *filter_ctx = ret;
-    return 0;
+    return ret;
 
 err:
     av_freep(&ret->inputs);
@@ -416,9 +414,17 @@ err:
     ret->nb_outputs = 0;
     av_freep(&ret->priv);
     av_free(ret);
-    return AVERROR(ENOMEM);
+    return NULL;
 }
 
+#if FF_API_AVFILTER_OPEN
+int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name)
+{
+    *filter_ctx = ff_filter_alloc(filter, inst_name);
+    return *filter_ctx ? 0 : AVERROR(ENOMEM);
+}
+#endif
+
 void avfilter_free(AVFilterContext *filter)
 {
     int i;

libavfilter/avfilter.h

@@ -602,8 +602,8 @@ void avfilter_uninit(void);
 /**
  * Register a filter. This is only needed if you plan to use
  * avfilter_get_by_name later to lookup the AVFilter structure by name. A
- * filter can still by instantiated with avfilter_open even if it is not
- * registered.
+ * filter can still by instantiated with avfilter_graph_alloc_filter even if it
+ * is not registered.
  *
  * @param filter the filter to register
  * @return 0 if the registration was succesfull, a negative value
@@ -628,6 +628,7 @@ AVFilter *avfilter_get_by_name(const char *name);
  */
 AVFilter **av_filter_next(AVFilter **filter);
 
+#if FF_API_AVFILTER_OPEN
 /**
  * Create a filter instance.
  *
@@ -636,8 +637,11 @@ AVFilter **av_filter_next(AVFilter **filter);
  * @param filter    the filter to create an instance of
  * @param inst_name Name to give to the new instance. Can be NULL for none.
  * @return >= 0 in case of success, a negative error code otherwise
+ * @deprecated use avfilter_graph_alloc_filter() instead
  */
+attribute_deprecated
 int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name);
+#endif
 
 /**
  * Initialize a filter.
@@ -720,6 +724,24 @@ typedef struct AVFilterGraph {
  */
 AVFilterGraph *avfilter_graph_alloc(void);
 
+/**
+ * Create a new filter instance in a filter graph.
+ *
+ * @param graph graph in which the new filter will be used
+ * @param filter the filter to create an instance of
+ * @param name Name to give to the new instance (will be copied to
+ *             AVFilterContext.name). This may be used by the caller to identify
+ *             different filters, libavfilter itself assigns no semantics to
+ *             this parameter. May be NULL.
+ *
+ * @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.
+ */
+AVFilterContext *avfilter_graph_alloc_filter(AVFilterGraph *graph,
+                                             const AVFilter *filter,
+                                             const char *name);
+
 /**
  * Get a filter instance with name name from graph.
  *

libavfilter/avfiltergraph.c

@@ -81,12 +81,12 @@ int avfilter_graph_create_filter(AVFilterContext **filt_ctx, AVFilter *filt,
 {
     int ret;
 
-    if ((ret = avfilter_open(filt_ctx, filt, name)) < 0)
-        goto fail;
+    *filt_ctx = avfilter_graph_alloc_filter(graph_ctx, filt, name);
+    if (!*filt_ctx)
+        return AVERROR(ENOMEM);
     if ((ret = avfilter_init_filter(*filt_ctx, args, opaque)) < 0)
         goto fail;
-    if ((ret = avfilter_graph_add_filter(graph_ctx, *filt_ctx)) < 0)
-        goto fail;
+
     return 0;
 
 fail:
@@ -96,6 +96,32 @@ fail:
     return ret;
 }
 
+AVFilterContext *avfilter_graph_alloc_filter(AVFilterGraph *graph,
+                                             const AVFilter *filter,
+                                             const char *name)
+{
+    AVFilterContext **filters, *s;
+
+    s = ff_filter_alloc(filter, name);
+    if (!s)
+        return NULL;
+
+    filters = av_realloc(graph->filters, sizeof(*filters) * (graph->nb_filters + 1));
+    if (!filters) {
+        avfilter_free(s);
+        return NULL;
+    }
+
+    graph->filters = filters;
+    graph->filters[graph->nb_filters++] = s;
+
+#if FF_API_FOO_COUNT
+    graph->filter_count = graph->nb_filters;
+#endif
+
+    return s;
+}
+
 /**
  * Check for the validity of graph.
  *

libavfilter/graphparser.c

@@ -109,16 +109,11 @@ static int create_filter(AVFilterContext **filt_ctx, AVFilterGraph *ctx, int ind
         return AVERROR(EINVAL);
     }
 
-    ret = avfilter_open(filt_ctx, filt, inst_name);
+    *filt_ctx = avfilter_graph_alloc_filter(ctx, filt, inst_name);
     if (!*filt_ctx) {
         av_log(log_ctx, AV_LOG_ERROR,
                "Error creating filter '%s'\n", filt_name);
-        return ret;
-    }
-
-    if ((ret = avfilter_graph_add_filter(ctx, *filt_ctx)) < 0) {
-        avfilter_free(*filt_ctx);
-        return ret;
+        return AVERROR(ENOMEM);
     }
 
     if (!strcmp(filt_name, "scale") && args && !strstr(args, "flags") &&

libavfilter/internal.h

@@ -196,4 +196,14 @@ int ff_request_frame(AVFilterLink *link);
  */
 int ff_filter_frame(AVFilterLink *link, AVFrame *frame);
 
+/**
+ * Allocate a new filter context and return it.
+ *
+ * @param filter what filter to create an instance of
+ * @param inst_name name to give to the new filter context
+ *
+ * @return newly created filter context or NULL on failure
+ */
+AVFilterContext *ff_filter_alloc(const AVFilter *filter, const char *inst_name);
+
 #endif /* AVFILTER_INTERNAL_H */

libavfilter/version.h

@@ -58,5 +58,8 @@
 #ifndef FF_API_OLD_FILTER_OPTS
 #define FF_API_OLD_FILTER_OPTS              (LIBAVFILTER_VERSION_MAJOR < 4)
 #endif
+#ifndef FF_API_AVFILTER_OPEN
+#define FF_API_AVFILTER_OPEN                (LIBAVFILTER_VERSION_MAJOR < 4)
+#endif
 
 #endif /* AVFILTER_VERSION_H */