diff --git a/coreapi/linphonecore.c b/coreapi/linphonecore.c
index 4ae24d0e9..a6911b301 100644
--- a/coreapi/linphonecore.c
+++ b/coreapi/linphonecore.c
@@ -2159,6 +2159,13 @@ bool_t linphone_core_inc_invite_pending(LinphoneCore*lc){
 	return FALSE;
 }
 
+#ifdef TEST_EXT_RENDERER
+static void rendercb(void *data, const MSPicture *local, const MSPicture *remote){
+	ms_message("rendercb, local buffer=%p, remote buffer=%p",
+	           local ? local->planes[0] : NULL, remote? remote->planes[0] : NULL);
+}
+#endif
+
 void linphone_core_init_media_streams(LinphoneCore *lc, LinphoneCall *call){
 	SalMediaDescription *md=call->localdesc;
 	lc->audiostream=audio_stream_new(md->streams[0].port,linphone_core_ipv6_enabled(lc));
@@ -2186,8 +2193,12 @@ void linphone_core_init_media_streams(LinphoneCore *lc, LinphoneCall *call){
 		rtp_session_set_transports(lc->audiostream->session,lc->a_rtp,lc->a_rtcp);
 
 #ifdef VIDEO_ENABLED
-	if ((lc->video_conf.display || lc->video_conf.capture) && md->streams[1].port>0)
+	if ((lc->video_conf.display || lc->video_conf.capture) && md->streams[1].port>0){
 		lc->videostream=video_stream_new(md->streams[1].port,linphone_core_ipv6_enabled(lc));
+#ifdef TEST_EXT_RENDERER
+		video_stream_set_render_callback(lc->videostream,rendercb,NULL);
+#endif
+	}
 #else
 	lc->videostream=NULL;
 #endif
@@ -2661,7 +2672,11 @@ void linphone_core_set_ring_level(LinphoneCore *lc, int level){
 	if (sndcard) ms_snd_card_set_level(sndcard,MS_SND_CARD_PLAYBACK,level);
 }
 
-
+/**
+ * Sets call playback gain in db
+ *
+ * @ingroup media_parameters
+**/
 void linphone_core_set_soft_play_level(LinphoneCore *lc, float level){
 	float gain=level;
 	lc->sound_conf.soft_play_lev=level;
@@ -2672,11 +2687,17 @@ void linphone_core_set_soft_play_level(LinphoneCore *lc, float level){
 		ms_filter_call_method(st->volrecv,MS_VOLUME_SET_DB_GAIN,&gain);
 	}else ms_warning("Could not apply gain: gain control wasn't activated.");
 }
+
+/**
+ * Returns call playback gain in db
+ *
+ * @ingroup media_parameters
+**/
 float linphone_core_get_soft_play_level(LinphoneCore *lc) {
 	float gain=0;
 	AudioStream *st=lc->audiostream;
 	if (st->volrecv){
-		ms_filter_call_method(st->volrecv,MS_VOLUME_GET,&gain);
+		ms_filter_call_method(st->volrecv,MS_VOLUME_GET_GAIN_DB,&gain);
 	}else ms_warning("Could not get gain: gain control wasn't activated.");
 
 	return gain;