diff --git a/spa/plugins/filter-graph/filter-graph.c b/spa/plugins/filter-graph/filter-graph.c
index bf2a57f7f..70de19d6b 100644
--- a/spa/plugins/filter-graph/filter-graph.c
+++ b/spa/plugins/filter-graph/filter-graph.c
@@ -1030,11 +1030,6 @@ static struct descriptor *descriptor_load(struct impl *impl, const char *type,
 			}
 		}
 	}
-	if (desc->n_input == 0 && desc->n_output == 0 && desc->n_control == 0 && desc->n_notify == 0) {
-		spa_log_error(impl->log, "plugin has no input and no output ports");
-		res = -ENOTSUP;
-		goto exit;
-	}
 	for (i = 0; i < desc->n_control; i++) {
 		p = desc->control[i];
 		desc->default_control[i] = get_default(impl, desc, p);
@@ -1794,7 +1789,7 @@ static int setup_graph(struct graph *graph)
 	struct port *port;
 	struct graph_port *gp;
 	struct graph_hndl *gh;
-	uint32_t i, j, n, n_input, n_output, n_hndl = 0;
+	uint32_t i, j, n, n_input, n_output, n_hndl = 0, n_out_hndl;
 	int res;
 	struct descriptor *desc;
 	const struct spa_fga_descriptor *d;
@@ -1815,16 +1810,11 @@ static int setup_graph(struct graph *graph)
 	    SPA_FLAG_IS_SET(first->desc->desc->flags, SPA_FGA_DESCRIPTOR_SUPPORTS_NULL_DATA) &&
 	    SPA_FLAG_IS_SET(last->desc->desc->flags, SPA_FGA_DESCRIPTOR_SUPPORTS_NULL_DATA);
 
-	if (n_input == 0) {
-		spa_log_error(impl->log, "no inputs");
-		res = -EINVAL;
-		goto error;
-	}
-	if (n_output == 0) {
-		spa_log_error(impl->log, "no outputs");
-		res = -EINVAL;
-		goto error;
-	}
+	if (n_input == 0)
+		n_input = n_output;
+	if (n_output == 0)
+		n_output = n_input;
+
 	if (graph->n_inputs == 0)
 		graph->n_inputs = impl->info.n_inputs;
 	if (graph->n_inputs == 0)
@@ -1835,12 +1825,14 @@ static int setup_graph(struct graph *graph)
 
 	/* compare to the requested number of inputs and duplicate the
 	 * graph n_hndl times when needed. */
-	n_hndl = graph->n_inputs / n_input;
+	n_hndl = n_input ? graph->n_inputs / n_input : 1;
 
 	if (graph->n_outputs == 0)
 		graph->n_outputs = n_output * n_hndl;
 
-	if (n_hndl != graph->n_outputs / n_output) {
+	n_out_hndl = n_output ? graph->n_outputs / n_output : 1;
+
+	if (n_hndl != n_out_hndl) {
 		spa_log_error(impl->log, "invalid ports. The input stream has %1$d ports and "
 				"the filter has %2$d inputs. The output stream has %3$d ports "
 				"and the filter has %4$d outputs. input:%1$d / input:%2$d != "
diff --git a/spa/plugins/filter-graph/plugin_builtin.c b/spa/plugins/filter-graph/plugin_builtin.c
index 8a964ccd7..69ed34fc2 100644
--- a/spa/plugins/filter-graph/plugin_builtin.c
+++ b/spa/plugins/filter-graph/plugin_builtin.c
@@ -14,6 +14,7 @@
 #include <sys/wait.h>
 #include <sys/socket.h>
 #include <fcntl.h>
+#include <time.h>
 
 #include <spa/utils/json.h>
 #include <spa/utils/result.h>
@@ -3115,6 +3116,107 @@ static const struct spa_fga_descriptor noisegate_desc = {
 	.cleanup = builtin_cleanup,
 };
 
+/* busy */
+struct busy_impl {
+	struct plugin *plugin;
+
+	struct spa_fga_dsp *dsp;
+	struct spa_log *log;
+
+	unsigned long rate;
+
+	float wait_scale;
+	float cpu_scale;
+};
+
+static void *busy_instantiate(const struct spa_fga_plugin *plugin, const struct spa_fga_descriptor * Descriptor,
+		unsigned long SampleRate, int index, const char *config)
+{
+	struct plugin *pl = SPA_CONTAINER_OF(plugin, struct plugin, plugin);
+	struct busy_impl *impl;
+	struct spa_json it[1];
+	const char *val;
+	char key[256];
+	float wait_percent = 0.0f, cpu_percent = 0.0f;
+	int len;
+
+	if (config != NULL) {
+		if (spa_json_begin_object(&it[0], config, strlen(config)) <= 0) {
+			spa_log_error(pl->log, "busy:config must be an object");
+			return NULL;
+		}
+
+		while ((len = spa_json_object_next(&it[0], key, sizeof(key), &val)) > 0) {
+			if (spa_streq(key, "wait-percent")) {
+				if (spa_json_parse_float(val, len, &wait_percent) <= 0) {
+					spa_log_error(pl->log, "busy:wait-percent requires a number");
+					return NULL;
+				}
+			} else if (spa_streq(key, "cpu-percent")) {
+				if (spa_json_parse_float(val, len, &cpu_percent) <= 0) {
+					spa_log_error(pl->log, "busy:cpu-percent requires a number");
+					return NULL;
+				}
+			} else {
+				spa_log_warn(pl->log, "busy: ignoring config key: '%s'", key);
+			}
+		}
+		if (wait_percent <= 0.0f)
+			wait_percent = 0.0f;
+		if (cpu_percent <= 0.0f)
+			cpu_percent = 0.0f;
+	}
+
+	impl = calloc(1, sizeof(*impl));
+	if (impl == NULL)
+		return NULL;
+
+	impl->plugin = pl;
+	impl->dsp = pl->dsp;
+	impl->log = pl->log;
+	impl->rate = SampleRate;
+	impl->wait_scale = wait_percent * SPA_NSEC_PER_SEC / (100.0f * SampleRate);
+	impl->cpu_scale = cpu_percent * SPA_NSEC_PER_SEC / (100.0f * SampleRate);
+	spa_log_info(impl->log, "wait-percent:%f cpu-percent:%f", wait_percent, cpu_percent);
+
+	return impl;
+}
+
+static void busy_run(void * Instance, unsigned long SampleCount)
+{
+	struct busy_impl *impl = Instance;
+	struct timespec ts;
+	uint64_t busy_nsec;
+
+	if (impl->wait_scale > 0.0f) {
+		busy_nsec = (uint64_t)(impl->wait_scale * SampleCount);
+		ts.tv_sec = busy_nsec / SPA_NSEC_PER_SEC;
+		ts.tv_nsec = busy_nsec % SPA_NSEC_PER_SEC;
+		clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
+	}
+	if (impl->cpu_scale > 0.0f) {
+		clock_gettime(CLOCK_MONOTONIC, &ts);
+		busy_nsec = SPA_TIMESPEC_TO_NSEC(&ts);
+		busy_nsec += (uint64_t)(impl->cpu_scale * SampleCount);
+		do {
+			clock_gettime(CLOCK_MONOTONIC, &ts);
+		} while ((uint64_t)SPA_TIMESPEC_TO_NSEC(&ts) < busy_nsec);
+	}
+}
+
+static const struct spa_fga_descriptor busy_desc = {
+	.name = "busy",
+	.flags = SPA_FGA_DESCRIPTOR_SUPPORTS_NULL_DATA,
+
+	.n_ports = 0,
+	.ports = NULL,
+
+	.instantiate = busy_instantiate,
+	.connect_port = builtin_connect_port,
+	.run = busy_run,
+	.cleanup = builtin_cleanup,
+};
+
 static const struct spa_fga_descriptor * builtin_descriptor(unsigned long Index)
 {
 	switch(Index) {
@@ -3180,6 +3282,8 @@ static const struct spa_fga_descriptor * builtin_descriptor(unsigned long Index)
 		return &zeroramp_desc;
 	case 30:
 		return &noisegate_desc;
+	case 31:
+		return &busy_desc;
 	}
 	return NULL;
 }
diff --git a/src/modules/module-filter-chain.c b/src/modules/module-filter-chain.c
index 9a723a859..9ab3639bd 100644
--- a/src/modules/module-filter-chain.c
+++ b/src/modules/module-filter-chain.c
@@ -652,6 +652,36 @@ extern struct spa_handle_factory spa_filter_graph_factory;
  * of "Attack (s)" seconds. The noise gate stays open for at least "Hold (s)"
  * seconds before it can close again.
  *
+ * ### Busy
+ *
+ * The `busy` plugin has no input or output ports and it can be used to keep the
+ * CPU or graph busy for the given percent of time.
+ *
+ * The node requires a `config` section with extra configuration:
+ *
+ *\code{.unparsed}
+ * filter.graph = {
+ *     nodes = [
+ *         {
+ *             type   = builtin
+ *             name   = ...
+ *             label  = busy
+ *             config = {
+ *                 wait-percent = 0.0
+ *                 cpu-percent = 50.0
+ *             }
+ *             ...
+ *         }
+ *     }
+ *     ...
+ * }
+ *\endcode
+ *
+ * - `wait-percent` the percentage of time to wait. This keeps the graph busy but
+ *                  not the CPU. Default 0.0
+ * - `cpu-percent` the percentage of time to keep the CPU busy. This keeps both the
+ *                  graph and CPU busy. Default 0.0
+ *
  *
  * ## SOFA filters
  *