Improve step parameter parsing and usage

README.md

@@ -138,7 +138,7 @@ Compression tools:
                                    - full8, full16, full32, full64
                                    - dia:   Diamond Search
       --me-steps <integer>   : How many search steps does the motion estimation
-                               do before cutting off, -1 for no limits [-1]
+                               do before cutting off [-1]
                                    Has effect only for 'hexbs' and 'dia'
       --subme <integer>      : Set fractional pixel motion estimation level
                                    - 0: only integer motion estimation

src/cfg.c

@@ -1156,7 +1156,21 @@ int kvz_config_parse(kvz_config *cfg, const char *name, const char *value)
     cfg->high_tier = true;
   }
   else if (OPT("me-steps")) {
-    cfg->me_max_steps = (uint32_t)atoi(value); // fix
+    char * tailptr = NULL;
+
+    errno = 0;
+    long steps = strtol(value, &tailptr, 0);
+
+    if (*tailptr != '\0') {
+      fprintf(stderr, "Invalid me-steps value: \"%s\"", value);
+      return 0;
+    }
+    if (steps < -1 || errno == ERANGE || steps > UINT32_MAX) {
+      fprintf(stderr, "me-steps value is out of bounds: \"%s\"", value);
+      return 0;
+    }
+
+    cfg->me_max_steps = (uint32_t)steps;
   }
   else {
     return 0;

src/cli.c

@@ -433,7 +433,7 @@ void print_help(void)
     "                                   - full8, full16, full32, full64\n"
     "                                   - dia:   Diamond Search\n"
     "      --me-steps <integer>   : How many search steps does the motion estimation\n"
-    "                               do before cutting off, -1 for no limits [-1]\n"
+    "                               do before cutting off [-1]\n"
     "                                   Has effect only for 'hexbs' and 'dia'\n"
     "      --subme <integer>      : Set fractional pixel motion estimation level\n"
     "                                   - 0: only integer motion estimation\n"

src/search_inter.c

@@ -630,6 +630,7 @@ static void tz_search(inter_search_info_t *info, vector2d_t extra_mv)
  *
  * \param info      search info
  * \param extra_mv  extra motion vector to check
+ * \param steps     how many steps are done at maximum before exiting, does not affect the final step
  *
  * Motion vector is searched by first searching iteratively with the large
  * hexagon pattern until the best match is at the center of the hexagon.
@@ -640,7 +641,7 @@ static void tz_search(inter_search_info_t *info, vector2d_t extra_mv)
  * the predicted motion vector is way off. In the future even more additional
  * points like 0,0 might be used, such as vectors from top or left.
  */
-static void hexagon_search(inter_search_info_t *info, vector2d_t extra_mv, uint32_t max_steps)
+static void hexagon_search(inter_search_info_t *info, vector2d_t extra_mv, uint32_t steps)
 {
   // The start of the hexagonal pattern has been repeated at the end so that
   // the indices between 1-6 can be used as the start of a 3-point list of new
@@ -689,13 +690,11 @@ static void hexagon_search(inter_search_info_t *info, vector2d_t extra_mv, uint3
     }
   }
 
-  uint32_t steps_left = max_steps;
-
   // Iteratively search the 3 new points around the best match, until the best
   // match is in the center.
-  while (best_index != 0 && steps_left != 0) {
+  while (best_index != 0 && steps != 0) {
     // decrement count if enabled
-    if (steps_left > 0 && max_steps != (uint32_t)-1) steps_left -= 1;
+    if (steps > 0) steps -= 1;
 
     // Starting point of the 3 offsets to be searched.
     unsigned start;
@@ -731,8 +730,23 @@ static void hexagon_search(inter_search_info_t *info, vector2d_t extra_mv, uint3
   }
 }
 
-
-static void diamond_search(inter_search_info_t *info, vector2d_t extra_mv, uint32_t max_steps) 
+/**
+* \brief Do motion search using the diamond algorithm.
+*
+* \param info      search info
+* \param extra_mv  extra motion vector to check
+* \param steps     how many steps are done at maximum before exiting
+*
+* Motion vector is searched by searching iteratively with a diamond-shaped
+* pattern. We take care of not checking the direction we came from, but
+* further checking for avoiding visits to already visited points is not done.
+*
+* If a non 0,0 predicted motion vector predictor is given as extra_mv,
+* the 0,0 vector is also tried. This is hoped to help in the case where
+* the predicted motion vector is way off. In the future even more additional
+* points like 0,0 might be used, such as vectors from top or left.
+**/
+static void diamond_search(inter_search_info_t *info, vector2d_t extra_mv, uint32_t steps) 
 {
   enum diapos {
     DIA_UP = 0,
@@ -791,12 +805,11 @@ static void diamond_search(inter_search_info_t *info, vector2d_t extra_mv, uint3
 
   // whether we found a better candidate this iteration
   uint8_t better_found;
-  uint32_t steps_left = max_steps;
 
   do {
     better_found = 0;
     // decrement count if enabled
-    if (steps_left > 0 && max_steps != (uint32_t) -1) steps_left -= 1;
+    if (steps > 0) steps -= 1;
 
     // search the points of the diamond
     for (int i = 0; i < 4; ++i) {
@@ -818,7 +831,7 @@ static void diamond_search(inter_search_info_t *info, vector2d_t extra_mv, uint3
       // the xor operation flips the orientation
       from_dir = best_index ^ 0x3;
     }
-  } while (better_found && steps_left != 0);
+  } while (better_found && steps != 0);
   // and we're done
 }