Require key-value data file syntax

README.md

@@ -107,39 +107,33 @@ Files are ordered by filename, so names like this work well:
 
 ## data.txt
 
-`data.txt` is optional.
+`data.txt` is optional, but if present every non-empty, non-comment line must use mandatory `key: value` syntax. Plain positional lines are not supported.
 
-Simplest format:
+Movie metadata keys:
 
 ```text
-Paris Trip
-Paris, France
-May 2024
+Title: Paris Trip
+Location: Paris, France
+Date: May 2024
+Description: Longer description shown in MVLog and embedded in final MP4 metadata.
 ```
 
-Those three lines mean:
+Supported metadata key aliases:
 
-1. title
-2. location
-3. date
+- title: `Title` or `Name`
+- location: `Location`, `Place`, or `Where`
+- date: `Date`, `Dates`, or `When`
+- description: `Description`, `Desc`, or `Synopsis`
 
-If the date line is omitted, movmaker uses the date from the first picture/video and displays it like:
+If the date entry is omitted, movmaker uses the date from the first picture/video and displays it like:
 
 ```text
 May 2026
 ```
 
-If the location line is omitted and GPS coordinates are found in the first picture/video that has them, movmaker reverse geocodes them and uses that as the location. It tries to return only `city/town/village, country`; if no city/town/village is found, it uses just the country.
+If the location entry is omitted and GPS coordinates are found in the first picture/video that has them, movmaker reverse geocodes them and uses that as the location. It tries to return only `city/town/village, country`; if no city/town/village is found, it uses just the country.
 
-Key/value format also works:
-
-```text
-title: Paris Trip
-date: May 2024
-place: Paris, France
-```
-
-Optional per-file captions are supported:
+Any other `key: value` line is treated as a per-file caption where the key is the exact media filename:
 
 ```text
 IMG_001.jpg: Eiffel Tower