mosaic_bridge: fully drain the video filter when the input source changes

modules/stream_out/mosaic_bridge.c

@@ -622,12 +622,30 @@ static int Send( sout_stream_t *p_stream, void *id, block_t *p_buffer )
     return ret == VLCDEC_SUCCESS ? VLC_SUCCESS : VLC_EGENERIC;
 }
 
+static void drain_filter(sout_stream_sys_t *p_sys)
+{
+    bridged_es_t *p_es = p_sys->p_es;
+    picture_t * p_in = NULL;
+    do
+    {
+        p_in = filter_chain_VideoDrain( p_sys->p_vf2, true );
+        if( p_in )
+        {
+            vlc_global_lock( VLC_MOSAIC_MUTEX );
+            vlc_picture_chain_Append( &p_es->pictures, p_in );
+            vlc_global_unlock( VLC_MOSAIC_MUTEX );
+        }
+    } while (p_in != NULL);
+}
+
 static int video_update_format_decoder( decoder_t *p_dec, vlc_video_context *vctx )
 {
     struct decoder_owner *p_owner = dec_get_owner( p_dec );
     sout_stream_sys_t *p_sys = p_owner->p_stream->p_sys;
     if ( p_sys->p_vf2 )
     {
+        drain_filter( p_sys );
+
         // update the filter after the format changed/is known
         char *psz_chain = var_GetNonEmptyString( p_owner->p_stream, CFG_PREFIX "vfilter" );
         msg_Dbg( p_owner->p_stream, "update filter: '%s'",