diff --git a/pinos/client/stream.c b/pinos/client/stream.c
index fff1f43ef..e752352a0 100644
--- a/pinos/client/stream.c
+++ b/pinos/client/stream.c
@@ -135,18 +135,20 @@ clear_buffers (PinosStream *stream)
   spa_list_init (&impl->free);
 }
 
-static void
+static bool
 stream_set_state (PinosStream      *stream,
                   PinosStreamState  state,
                   char             *error)
 {
-  if (stream->state != state) {
+  bool res = stream->state != state;
+  if (res) {
     if (stream->error)
       free (stream->error);
     stream->error = error;
     stream->state = state;
     pinos_signal_emit (&stream->state_changed, stream);
   }
+  return res;
 }
 
 /**
@@ -604,32 +606,37 @@ handle_node_command (PinosStream      *stream,
   PinosContext *context = stream->context;
 
   if (SPA_COMMAND_TYPE (command) == context->type.command_node.Pause) {
-    pinos_log_debug ("stream %p: pause %d", stream, seq);
-
-    pinos_loop_update_io (stream->context->loop,
-                          impl->rtsocket_source,
-                          SPA_IO_ERR | SPA_IO_HUP);
-
     add_async_complete (stream, seq, SPA_RESULT_OK);
-    stream_set_state (stream, PINOS_STREAM_STATE_PAUSED, NULL);
+
+    if (stream->state == PINOS_STREAM_STATE_STREAMING) {
+      pinos_log_debug ("stream %p: pause %d", stream, seq);
+
+      pinos_loop_update_io (stream->context->loop,
+                            impl->rtsocket_source,
+                            SPA_IO_ERR | SPA_IO_HUP);
+
+      stream_set_state (stream, PINOS_STREAM_STATE_PAUSED, NULL);
+    }
   }
   else if (SPA_COMMAND_TYPE (command) == context->type.command_node.Start) {
-    pinos_log_debug ("stream %p: start %d %d", stream, seq, impl->direction);
     add_async_complete (stream, seq, SPA_RESULT_OK);
 
-    pinos_loop_update_io (stream->context->loop,
-                          impl->rtsocket_source,
-                          SPA_IO_IN | SPA_IO_ERR | SPA_IO_HUP);
+    if (stream->state == PINOS_STREAM_STATE_PAUSED) {
+      pinos_log_debug ("stream %p: start %d %d", stream, seq, impl->direction);
 
-    if (impl->direction == SPA_DIRECTION_INPUT)
-      send_need_input (stream);
-    else {
-      impl->in_need_buffer = true;
-      pinos_signal_emit (&stream->need_buffer, stream);
-      impl->in_need_buffer = false;
+      pinos_loop_update_io (stream->context->loop,
+                            impl->rtsocket_source,
+                            SPA_IO_IN | SPA_IO_ERR | SPA_IO_HUP);
+
+      if (impl->direction == SPA_DIRECTION_INPUT)
+        send_need_input (stream);
+      else {
+        impl->in_need_buffer = true;
+        pinos_signal_emit (&stream->need_buffer, stream);
+        impl->in_need_buffer = false;
+      }
+      stream_set_state (stream, PINOS_STREAM_STATE_STREAMING, NULL);
     }
-
-    stream_set_state (stream, PINOS_STREAM_STATE_STREAMING, NULL);
   }
   else if (SPA_COMMAND_TYPE (command) == context->type.command_node.ClockUpdate) {
     SpaCommandNodeClockUpdate *cu = (SpaCommandNodeClockUpdate *) command;
@@ -660,6 +667,8 @@ client_node_done (void              *object,
   pinos_log_info ("strean %p: create client node done with fd %d", stream, datafd);
   handle_socket (stream, datafd);
   do_node_init (stream);
+
+  stream_set_state (stream, PINOS_STREAM_STATE_CONFIGURE, NULL);
 }
 
 static void
@@ -703,11 +712,15 @@ client_node_set_format (void              *object,
 
   if (impl->format)
     free (impl->format);
-  impl->format = spa_format_copy (format);
+  impl->format = format ? spa_format_copy (format) : NULL;
   impl->pending_seq = seq;
 
   pinos_signal_emit (&stream->format_changed, stream, impl->format);
-  stream_set_state (stream, PINOS_STREAM_STATE_READY, NULL);
+
+  if (format)
+    stream_set_state (stream, PINOS_STREAM_STATE_READY, NULL);
+  else
+    stream_set_state (stream, PINOS_STREAM_STATE_CONFIGURE, NULL);
 }
 
 static void
@@ -1038,7 +1051,7 @@ pinos_stream_finish_format (PinosStream     *stream,
   impl->port_info.n_params = n_params;
 
   if (SPA_RESULT_IS_OK (res)) {
-    add_port_update (stream, PINOS_MESSAGE_PORT_UPDATE_INFO |
+    add_port_update (stream, (n_params ? PINOS_MESSAGE_PORT_UPDATE_INFO : 0) |
                              PINOS_MESSAGE_PORT_UPDATE_FORMAT);
 
     if (!impl->format)
diff --git a/pinos/examples/video-src.c b/pinos/examples/video-src.c
index e2843e7a2..cb1870abf 100644
--- a/pinos/examples/video-src.c
+++ b/pinos/examples/video-src.c
@@ -69,6 +69,8 @@ typedef struct {
   PinosListener on_stream_state_changed;
   PinosListener on_stream_format_changed;
 
+  SpaVideoInfoRaw format;
+
   uint8_t params_buffer[1024];
   int counter;
 } Data;
@@ -170,19 +172,24 @@ on_stream_format_changed (PinosListener  *listener,
   SpaPODFrame f[2];
   SpaAllocParam *params[2];
 
-  spa_pod_builder_init (&b, data->params_buffer, sizeof (data->params_buffer));
-  spa_pod_builder_object (&b, &f[0], 0, ctx->type.alloc_param_buffers.Buffers,
-      PROP      (&f[1], ctx->type.alloc_param_buffers.size,    SPA_POD_TYPE_INT, STRIDE * HEIGHT),
-      PROP      (&f[1], ctx->type.alloc_param_buffers.stride,  SPA_POD_TYPE_INT, STRIDE),
-      PROP_U_MM (&f[1], ctx->type.alloc_param_buffers.buffers, SPA_POD_TYPE_INT, 32, 2, 32),
-      PROP      (&f[1], ctx->type.alloc_param_buffers.align,   SPA_POD_TYPE_INT, 16));
-  params[0] = SPA_POD_BUILDER_DEREF (&b, f[0].ref, SpaAllocParam);
+  if (format) {
+    spa_pod_builder_init (&b, data->params_buffer, sizeof (data->params_buffer));
+    spa_pod_builder_object (&b, &f[0], 0, ctx->type.alloc_param_buffers.Buffers,
+        PROP      (&f[1], ctx->type.alloc_param_buffers.size,    SPA_POD_TYPE_INT, STRIDE * HEIGHT),
+        PROP      (&f[1], ctx->type.alloc_param_buffers.stride,  SPA_POD_TYPE_INT, STRIDE),
+        PROP_U_MM (&f[1], ctx->type.alloc_param_buffers.buffers, SPA_POD_TYPE_INT, 32, 2, 32),
+        PROP      (&f[1], ctx->type.alloc_param_buffers.align,   SPA_POD_TYPE_INT, 16));
+    params[0] = SPA_POD_BUILDER_DEREF (&b, f[0].ref, SpaAllocParam);
 
-  spa_pod_builder_object (&b, &f[0], 0, ctx->type.alloc_param_meta_enable.MetaEnable,
-    PROP      (&f[1], ctx->type.alloc_param_meta_enable.type, SPA_POD_TYPE_INT, SPA_META_TYPE_HEADER));
-  params[1] = SPA_POD_BUILDER_DEREF (&b, f[0].ref, SpaAllocParam);
+    spa_pod_builder_object (&b, &f[0], 0, ctx->type.alloc_param_meta_enable.MetaEnable,
+      PROP      (&f[1], ctx->type.alloc_param_meta_enable.type, SPA_POD_TYPE_INT, SPA_META_TYPE_HEADER));
+    params[1] = SPA_POD_BUILDER_DEREF (&b, f[0].ref, SpaAllocParam);
 
-  pinos_stream_finish_format (stream, SPA_RESULT_OK, params, 2);
+    pinos_stream_finish_format (stream, SPA_RESULT_OK, params, 2);
+  }
+  else {
+    pinos_stream_finish_format (stream, SPA_RESULT_OK, NULL, 0);
+  }
 }
 
 static void
diff --git a/pinos/server/port.c b/pinos/server/port.c
index e16a69b51..731bd9e9a 100644
--- a/pinos/server/port.c
+++ b/pinos/server/port.c
@@ -203,6 +203,9 @@ static SpaResult
 pinos_port_pause (PinosPort *port)
 {
   SpaCommand cmd = SPA_COMMAND_INIT (port->node->core->type.command_node.Pause);
+  if (port->state <= SPA_PORT_STATE_PAUSED)
+    return SPA_RESULT_OK;
+
   port->state = SPA_PORT_STATE_PAUSED;
   return spa_node_port_send_command (port->node->node,
                                     port->direction,