[utils] Add codec2ext

diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 22a39a0ab7af191095242e6b2a3f580e59e17c37..dc0bf5627a5d149da4790b1f2d938649ed7924f9 100644 (file)
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1893,6 +1893,19 @@ def mimetype2ext(mt):
     }.get(res, res)
 
 
+def codec2ext(codec):
+    codec_type = codec.split('.')[0]
+
+    # Leave the return value None for unknown values as codec_type
+    # is not a good fallback for file extensions
+    return {
+        'avc1': 'mp4',
+        'mp4a': 'm4a',
+        'vorbis': 'webm',
+        'vp9': 'webm',
+    }.get(codec_type)
+
+
 def urlhandle_detect_ext(url_handle):
     try:
         url_handle.headers