[reddit] provide video previews if available (#4322)

gallery_dl/extractor/reddit.py

@@ -173,6 +173,16 @@ class RedditExtractor(Extractor):
         return submission["url"]
 
     def _previews(self, post):
+        try:
+            if "reddit_video_preview" in post["preview"]:
+                video = post["preview"]["reddit_video_preview"]
+                if "dash_url" in video:
+                    yield "ytdl:" + video["dash_url"]
+                if "hls_url" in video:
+                    yield "ytdl:" + video["hls_url"]
+        except Exception as exc:
+            self.log.debug("%s: %s", exc.__class__.__name__, exc)
+
         try:
             for image in post["preview"]["images"]:
                 yield image["source"]["url"]

gallery_dl/job.py

@@ -404,6 +404,8 @@ class DownloadJob(Job):
                                 pass
                             else:
                                 text.nameext_from_url(url, kwdict)
+                                if url.startswith("ytdl:"):
+                                    kwdict["extension"] = ""
                                 self.handle_url(url, kwdict)
                     break
                 except exception.RestartExtraction: