linux-v4l2: Improve module detection

Expand PATH for Debian-like systems.
Improve detection when the module is already loaded.

plugins/linux-v4l2/linux-v4l2.c

@@ -26,18 +26,7 @@ MODULE_EXPORT const char *obs_module_description(void)
 
 extern struct obs_source_info v4l2_input;
 extern struct obs_output_info virtualcam_info;
-
-static bool v4l2loopback_installed()
-{
-	bool loaded = false;
-
-	int ret = system("modinfo v4l2loopback >/dev/null 2>&1");
-
-	if (ret == 0)
-		loaded = true;
-
-	return loaded;
-}
+extern bool loopback_module_available();
 
 bool obs_module_load(void)
 {
@@ -45,7 +34,7 @@ bool obs_module_load(void)
 
 	obs_data_t *obs_settings = obs_data_create();
 
-	if (v4l2loopback_installed()) {
+	if (loopback_module_available()) {
 		obs_register_output(&virtualcam_info);
 		obs_data_set_bool(obs_settings, "vcamEnabled", true);
 	} else {

plugins/linux-v4l2/v4l2-output.c

@@ -50,10 +50,24 @@ static bool loopback_module_loaded()
 	return loaded;
 }
 
+bool loopback_module_available()
+{
+	if (loopback_module_loaded()) {
+		return true;
+	}
+
+	if (system("PATH=\"$PATH:/sbin\" modinfo v4l2loopback >/dev/null 2>&1") ==
+	    0) {
+		return true;
+	}
+
+	return false;
+}
+
 static int loopback_module_load()
 {
 	return system(
-		"pkexec modprobe v4l2loopback exclusive_caps=1 card_label='OBS Virtual Camera' && sleep 0.5");
+		"PATH=\"$PATH:/sbin\" pkexec modprobe v4l2loopback exclusive_caps=1 card_label='OBS Virtual Camera' && sleep 0.5");
 }
 
 static void *virtualcam_create(obs_data_t *settings, obs_output_t *output)