Documented the ability to force the language when generating subtitles

README.md

@@ -230,13 +230,20 @@ Values in `generate_subtitles` are objects with the following structure:
 
  * `type`: `string`  
    The transcription engine to be used for generating the subtitles. Currently
-   only supports the value "whisper".
+   only supports the value "whisper". This key is mandatory.
 
  * `source`: `string`  
    The name of one of this presentation's video streams, which will be used to
    generate the subtitle track. Should preferrably use a stream with a camera
    feed for best synchronization results. The stream may either be an already
-   existing one or one created by this job.
+   existing one or one created by this job. This key is mandatory.
+
+ * `language`: `string`  
+   The language in which to generate subtitles. If omitted, the language will
+   be inferred by the subtitling engine. Should mainly be used to force the
+   correct language when the automatic detection fails.  
+   The language string should be a two-letter ISO 639-1 language code, such as
+   `sv` or `en`.
 
 Here is an example of valid `subtitles` and `generate_subtitles` sections:
 ```json
@@ -246,19 +253,21 @@ Here is an example of valid `subtitles` and `generate_subtitles` sections:
         "Svenska": null
     },
     "generate_subtitles": {
-        "Generated": {
+        "English (generated)": {
             "type": "whisper",
-            "source": "camera"
+            "source": "camera",
+            "language": "en"
         }
     }
 }
 ```
+
 This example would save the provided WEBVTT file for the "English" track,
-generate subtitles for the "Generated" track based on the given source and
-delete the "Svenska" track. Note that the source "camera" must exist (either
-in this job specification or in the package already on disk in case of an
-update), and `upload_dir` must be provided in the job specification in order
-to be able to resolve the path to the English subtitle track.
+generate subtitles for the "English (generated)" track based on the given
+source and delete the "Svenska" track. Note that the source "camera" must
+exist (either in this job specification or in the package already on disk in
+case of an update), and `upload_dir` must be provided in the job specification
+in order to be able to resolve the path to the English subtitle track.
 
 
 ### Job Sources

pipeline/handlers/subtitles.py

@@ -39,8 +39,10 @@ def _do_whisper_transcribe(inpath,
                                     word_timestamps=True)
         end = time.time()
         if language is None:
-            read_language = result['language']
+            out_language = result['language']
             logger.info(f"Detected language '{read_language}' in {inpath}.")
+        else:
+            out_language = language
         vttWriter = whisper.utils.WriteVTT(str(outpath.parent))
         vttWriter.always_include_hours = True
     except Exception as e:
@@ -55,7 +57,7 @@ def _do_whisper_transcribe(inpath,
     elapsed = time.strftime('%H:%M:%S', time.gmtime(end - start))
     logger.info('Finished whisper transcription job '
                 f'for {inpath} in {elapsed}.')
-    return outpath
+    return (outpath, out_language)
 
 
 @Handler.register