diff --git a/include/mediastreamer2/mediastream.h b/include/mediastreamer2/mediastream.h
index 47e9546..00ce4f2 100644
--- a/include/mediastreamer2/mediastream.h
+++ b/include/mediastreamer2/mediastream.h
@@ -226,7 +226,7 @@ int video_stream_send_only_start(VideoStream *videostream,
 void video_stream_recv_only_stop(VideoStream *vs);
 void video_stream_send_only_stop(VideoStream *vs);
 
-VideoStream * video_preview_start(MSWebCam *device, MSVideoSize vsize);
+VideoStream * video_preview_start(MSWebCam *device, MSVideoSize disp_size, const char *displaytype);
 void video_preview_stop(VideoStream *stream);
 
 bool_t ms_is_ipv6(const char *address);
diff --git a/src/msv4l2.c b/src/msv4l2.c
index 1df88e6..94d89c3 100644
--- a/src/msv4l2.c
+++ b/src/msv4l2.c
@@ -382,7 +382,7 @@ static void msv4l2_uninit(MSFilter *f){
 	V4l2State *s=(V4l2State*)f->data;
 	ms_free(s->dev);
 #ifdef V4L2_THREADED
-	ms_mutex_destroy(&s->mutex);	
+	ms_mutex_destroy(&s->mutex);
 #endif
 	ms_free(s);
 }
@@ -390,7 +390,6 @@ static void msv4l2_uninit(MSFilter *f){
 #ifdef V4L2_THREADED
 static void *msv4l2_thread(void *ptr){
 	V4l2State *s=(V4l2State*)ptr;
-	int err=-1;
 	ms_message("msv4l2_thread starting");
 	if (s->fd!=-1)
 	{
@@ -407,13 +406,12 @@ static void *msv4l2_thread(void *ptr){
 	}
 	if (msv4l2_do_mmap(s)!=0)
 	{
-		ms_warning("msv4l2 do mmap");
+		ms_warning("msv4l2 could not do mmap");
 		goto close;
 	}
 	ms_message("V4L2 video capture started.");
 	while(s->thread_run)
 	{
-		mblk_t *m;
 		if (s->fd!=-1){
 			mblk_t *m;
 			m=v4lv2_grab_image(s);
@@ -425,9 +423,7 @@ static void *msv4l2_thread(void *ptr){
 				ms_mutex_unlock(&s->mutex);
 			}
 		}
-	}	
-	ms_message("thread:%d",s->thread_run);
-munmap:	
+	}
 	msv4l2_do_munmap(s);
 close:
 	msv4l2_close(s);
@@ -471,12 +467,12 @@ static void msv4l2_process(MSFilter *f){
 	
 	if (cur_frame>=s->frame_count){
 		mblk_t *om=NULL;
-		ms_mutex_lock(&s->mutex);
 		/*keep the most recent frame if several frames have been captured */
 		if (s->fd!=-1){
+			ms_mutex_lock(&s->mutex);
 			om=getq(&s->rq);
+			ms_mutex_unlock(&s->mutex);
 		}
-		ms_mutex_unlock(&s->mutex);
 		if (om!=NULL){
 			timestamp=f->ticker->time*90;/* rtp uses a 90000 Hz clockrate for video*/
 			mblk_set_timestamp_info(om,timestamp);
diff --git a/src/videostream.c b/src/videostream.c
index 47b44aa..44e9381 100644
--- a/src/videostream.c
+++ b/src/videostream.c
@@ -432,7 +432,7 @@ unsigned long video_stream_get_native_window_id(VideoStream *stream){
 }
 
 
-VideoStream * video_preview_start(MSWebCam *device, MSVideoSize disp_size){
+VideoStream * video_preview_start(MSWebCam *device, MSVideoSize disp_size, const char *displaytype){
 	VideoStream *stream = (VideoStream *)ms_new0 (VideoStream, 1);
 	MSVideoSize vsize=disp_size;
 	MSPixFmt format;
@@ -441,7 +441,10 @@ VideoStream * video_preview_start(MSWebCam *device, MSVideoSize disp_size){
 	int corner=-1;
 
 	/* creates the filters */
-	choose_display_name(stream);
+	if(!displaytype)
+		choose_display_name(stream);
+	else
+		video_stream_set_display_filter_name(stream,displaytype);
 	stream->source = ms_web_cam_create_reader(device);
 
 	stream->output=ms_filter_new_from_name (stream->display_name);
diff --git a/tests/videodisplay.c b/tests/videodisplay.c
index 4c69372..b42530a 100644
--- a/tests/videodisplay.c
+++ b/tests/videodisplay.c
@@ -37,7 +37,7 @@ int main(int argc, char *argv[]){
 	/* this is to test the sequence start/stop */
 	for(i=0;i<1;++i){
 		int n;
-		vs=video_preview_start(cam,vsize);
+		vs=video_preview_start(cam,vsize,NULL);
 
         	for(n=0;n<1000;++n){
 #ifdef WIN32