v4l2: calculate duration only once

modules/access/v4l2.c

@@ -560,6 +560,7 @@ struct demux_sys_t
     float f_fps;            /* <= 0.0 mean to grab at full rate */
     mtime_t i_video_pts;    /* only used when f_fps > 0 */
     int i_fourcc;
+    mtime_t i_duration;     /* frame duration calculation */
 
     es_out_id_t *p_es;
 
@@ -669,6 +670,8 @@ static int DemuxOpen( vlc_object_t *p_this )
 
     ParseMRL( p_sys, p_demux->psz_path, (vlc_object_t *) p_demux );
 
+    p_sys->i_duration = (mtime_t)((double)1000000 / (double)p_sys->f_fps);
+
 #ifdef HAVE_LIBV4L2
     if( !config_GetInt( p_this, CFG_PREFIX "use-libv4l2" ) )
     {
@@ -1298,10 +1301,8 @@ static block_t* GrabVideo( demux_t *p_demux )
 
     if( p_sys->f_fps >= 0.1 && p_sys->i_video_pts > 0 )
     {
-        mtime_t i_dur = (mtime_t)((double)1000000 / (double)p_sys->f_fps);
-
         /* Did we wait long enough ? (frame rate reduction) */
-        if( p_sys->i_video_pts + i_dur > mdate() ) return NULL;
+        if( p_sys->i_video_pts + p_sys->i_duration > mdate() ) return NULL;
     }
 
     /* Grab Video Frame */