[dl:http] add MIME type and signature for .aac files

gallery_dl/downloader/http.py

@@ -484,6 +484,8 @@ MIME_TYPES = {
     "audio/webm" : "webm",
     "audio/ogg"  : "ogg",
     "audio/mpeg" : "mp3",
+    "audio/aac"  : "aac",
+    "audio/x-aac": "aac",
 
     "application/vnd.apple.mpegurl": "m3u8",
     "application/x-mpegurl"        : "m3u8",
@@ -540,6 +542,7 @@ SIGNATURE_CHECKS = {
                        s[8:12] == b"WAVE"),
     "mp3" : lambda s: (s[0:3] == b"ID3" or
                        s[0:2] in (b"\xFF\xFB", b"\xFF\xF3", b"\xFF\xF2")),
+    "aac" : lambda s: s[0:2] in (b"\xFF\xF9", b"\xFF\xF1"),
     "m3u8": lambda s: s[0:7] == b"#EXTM3U",
     "mpd" : lambda s: b"<MPD" in s,
     "zip" : lambda s: s[0:4] in (b"PK\x03\x04", b"PK\x05\x06", b"PK\x07\x08"),

test/test_downloader.py

@@ -395,6 +395,8 @@ SAMPLES = {
     ("mp3" , b"\xFF\xFB"),
     ("mp3" , b"\xFF\xF3"),
     ("mp3" , b"\xFF\xF2"),
+    ("aac" , b"\xFF\xF9"),
+    ("aac" , b"\xFF\xF1"),
     ("m3u8", b"#EXTM3U\n#EXT-X-STREAM-INF:PROGRAM-ID=1, BANDWIDTH=200000"),
     ("mpd" , b'<MPD xmlns="urn:mpeg:dash:schema:mpd:2011"'),
     ("zip" , b"PK\x03\x04"),