diff --git a/lib/operators.c b/lib/operators.c
index 9decadf..1ffdd1a 100644
--- a/lib/operators.c
+++ b/lib/operators.c
@@ -15,6 +15,10 @@
 extern int verbosity;		/* must be declared around main() */
 
 /* ---------------------------------------------------------------- */
+/*
+ * 	A + B -> D
+ * 				why is this func so slow ?
+ */
 int fimg_add(FloatImg *a, FloatImg *b, FloatImg *d)
 {
 int		idx, nbiter;
@@ -57,6 +61,9 @@ if (3 != a->type || 3 != b->type || 3 != d->type) {
 
 nbiter = a->width * a->height;
 
+/*		maybe we can speedup this loop for
+ *		avoiding the cache strashing ?
+ */
 for (idx=0; idx<nbiter; idx++) {
 	d->R[idx] = fabs(a->R[idx] - b->R[idx]);
 	d->G[idx] = fabs(a->G[idx] - b->G[idx]);
diff --git a/v4l2/rgb2fimg.c b/v4l2/rgb2fimg.c
index f9a7237..ad1edba 100644
--- a/v4l2/rgb2fimg.c
+++ b/v4l2/rgb2fimg.c
@@ -41,6 +41,8 @@ for (y=0; y<h; y++) {
 		r = (float)*src++;
 		g = (float)*src++;
 		b = (float)*src++;
+
+		/* may be, here, we can speed up the job */
 		fimg_add_rgb(d, xx, yy, r, g, b);
 		}
 	}