avfilter: Add command passing support

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/avfilter.c

@@ -26,6 +26,7 @@
 #include "libavutil/audioconvert.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
 #include "avfilter.h"
 #include "internal.h"
 
@@ -616,6 +617,17 @@ void avfilter_draw_slice(AVFilterLink *link, int y, int h, int slice_dir)
     draw_slice(link, y, h, slice_dir);
 }
 
+int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags)
+{
+    if(!strcmp(cmd, "ping")){
+        av_strlcatf(res, res_len, "pong from:%s %s\n", filter->filter->name, filter->name);
+        return 0;
+    }else if(filter->filter->process_command) {
+        return filter->filter->process_command(filter, cmd, arg, res, res_len, flags);
+    }
+    return AVERROR(ENOSYS);
+}
+
 void avfilter_filter_samples(AVFilterLink *link, AVFilterBufferRef *samplesref)
 {
     void (*filter_samples)(AVFilterLink *, AVFilterBufferRef *);

libavfilter/avfilter.h

@@ -29,7 +29,7 @@
 #include "libavutil/rational.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 35
+#define LIBAVFILTER_VERSION_MINOR 36
 #define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
@@ -552,6 +552,20 @@ typedef struct AVFilter {
      * NULL_IF_CONFIG_SMALL() macro to define it.
      */
     const char *description;
+
+    /**
+     * Make the filter instance process a command.
+     *
+     * @param cmd    the command to process, for handling simplicity all commands must be alphanumeric only
+     * @param arg    the argument for the command
+     * @param res    a buffer with size res_size where the filter(s) can return a response. This must not change when the command is not supported.
+     * @param flags  if AVFILTER_CMD_FLAG_FAST is set and the command would be
+     *               timeconsuming then a filter should treat it like an unsupported command
+     *
+     * @returns >=0 on success otherwise an error code.
+     *          AVERROR(ENOSYS) on unsupported commands
+     */
+    int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);
 } AVFilter;
 
 /** An instance of a filter */
@@ -791,6 +805,15 @@ void avfilter_end_frame(AVFilterLink *link);
  */
 void avfilter_draw_slice(AVFilterLink *link, int y, int h, int slice_dir);
 
+#define AVFILTER_CMD_FLAG_ONE   1 ///< Stop once a filter understood the command (for target=all for example), fast filters are favored automatically
+#define AVFILTER_CMD_FLAG_FAST  2 ///< Only execute command when its fast (like a video out that supports contrast adjustment in hw)
+
+/**
+ * Make the filter instance process a command.
+ * It is recommanded to use avfilter_graph_send_command().
+ */
+int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags);
+
 /**
  * Send a buffer of audio samples to the next filter.
  *

libavfilter/avfiltergraph.c

@@ -253,3 +253,33 @@ int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx)
 
     return 0;
 }
+
+int avfilter_graph_send_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, char *res, int res_len, int flags)
+{
+    int i, r = AVERROR(ENOSYS);
+
+    if(!graph)
+        return r;
+
+    if((flags & AVFILTER_CMD_FLAG_ONE) && !(flags & AVFILTER_CMD_FLAG_FAST)) {
+        r=avfilter_graph_send_command(graph, target, cmd, arg, res, res_len, flags | AVFILTER_CMD_FLAG_FAST);
+        if(r != AVERROR(ENOSYS))
+            return r;
+    }
+
+    if(res_len && res)
+        res[0]= 0;
+
+    for (i = 0; i < graph->filter_count; i++) {
+        AVFilterContext *filter = graph->filters[i];
+        if(!strcmp(target, "all") || !strcmp(target, filter->name) || !strcmp(target, filter->filter->name)){
+            r = avfilter_process_command(filter, cmd, arg, res, res_len, flags);
+            if(r != AVERROR(ENOSYS)) {
+                if((flags & AVFILTER_CMD_FLAG_ONE) || r<0)
+                    return r;
+            }
+        }
+    }
+
+    return r;
+}

libavfilter/avfiltergraph.h

@@ -136,4 +136,21 @@ int avfilter_graph_parse(AVFilterGraph *graph, const char *filters,
                          AVFilterInOut **inputs, AVFilterInOut **outputs,
                          void *log_ctx);
 
+/**
+ * Send a command to one or more filter instances.
+ *
+ * @param graph  the filter graph
+ * @param target the filter(s) to which the command should be sent
+ *               "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 alphanumeric only
+ * @param arg    the argument for the command
+ * @param res    a buffer with size res_size where the filter(s) can return a response.
+ *
+ * @returns >=0 on success otherwise an error code.
+ *              AVERROR(ENOSYS) on unsupported commands
+ */
+int avfilter_graph_send_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, char *res, int res_len, int flags);
+
 #endif /* AVFILTER_AVFILTERGRAPH_H */