Add seek-in value option for video thumbnails

* Allows users to specify which percentage of the total video duration
to seek in instead of hardcoding 15%.
* Now defaults to 50%.

src/_h5ai/private/conf/options.json

@@ -356,6 +356,7 @@
     - doc: array of strings
     - delay: number, delay in milliseconds after "dom-ready" before thumb-requesting starts
     - size: number, size in pixel of the generated thumbnails
+    - seek: number, percentage of total video duration to seek into
     - exif: boolean, use included EXIF thumbs if possible
     - chunksize: int, number of thumbs per request
     */
@@ -366,6 +367,7 @@
         "doc": ["x-pdf", "x-ps"],
         "delay": 1,
         "size": 240,
+        "seek": 50,
         "exif": false,
         "chunksize": 20
     },

src/_h5ai/private/php/ext/class-thumb.php

@@ -124,13 +124,17 @@ private function compute_duration($cmdv, $source_path) {
         foreach ($cmdv as &$arg) {
             $arg = str_replace('[H5AI_SRC]', $source_path, $arg);
         }
-        $result = Util::exec_cmdv($cmdv);
-        if (empty($result) || !is_numeric($result) || is_infinite($result)) {
-            // Force seeking at 1 second in
-            return "1";
+        $duration = Util::exec_cmdv($cmdv);
+        if (empty($duration) || !is_numeric($duration) || is_infinite($duration)) {
+            return "0.1";
         }
-        // Seek at 15% of the total video duration
-        return strval(round(((floatval($result) * 15) / 100), 1, PHP_ROUND_HALF_UP));
+        // Seek at user-defined percentage of the total video duration
+        return strval(
+            round(
+            (floatval($duration) *
+            floatval($this->context->query_option('thumbnails.seek', 50)) / 100),
+            1, PHP_ROUND_HALF_UP)
+        );
     }
 }