From 765ac263dbf17442f41715a1cfce13fc61a4b315 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jaime=20Marqui=CC=81nez=20Ferra=CC=81ndiz?=
 <jaime.marquinez.ferrandiz@gmail.com>
Date: Sat, 20 Feb 2016 19:55:10 +0100
Subject: [PATCH] [utils] mimetype2ext: return 'm4a' for 'audio/mp4' (fixes
 #8620)

The youtube extractor was using 'mp4' for them, therefore filters like 'bestaudio[ext=m4a]' stopped working (94278f720272c5ad2cd5900f59f8e71f31d46633 broke it).
---
 youtube_dl/utils.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 7ce661b09e..a2c6780ca3 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1836,6 +1836,12 @@ def error_to_compat_str(err):
 
 
 def mimetype2ext(mt):
+    ext = {
+        'audio/mp4': 'm4a',
+    }.get(mt)
+    if ext is not None:
+        return ext
+
     _, _, res = mt.rpartition('/')
 
     return {