[downloader/ism] Support ec-3 codec (#5004)

Closes #296
Authored by: nixxo

yt_dlp/downloader/ism.py

@@ -138,6 +138,8 @@ def write_piff_header(stream, params):
 
         if fourcc == 'AACL':
             sample_entry_box = box(b'mp4a', sample_entry_payload)
+        if fourcc == 'EC-3':
+            sample_entry_box = box(b'ec-3', sample_entry_payload)
     elif stream_type == 'video':
         sample_entry_payload += u16.pack(0)  # pre defined
         sample_entry_payload += u16.pack(0)  # reserved

yt_dlp/extractor/common.py

@@ -3124,9 +3124,10 @@ class InfoExtractor:
             stream_name = stream.get('Name')
             stream_language = stream.get('Language', 'und')
             for track in stream.findall('QualityLevel'):
-                fourcc = track.get('FourCC') or ('AACL' if track.get('AudioTag') == '255' else None)
+                KNOWN_TAGS = {'255': 'AACL', '65534': 'EC-3'}
+                fourcc = track.get('FourCC') or KNOWN_TAGS.get(track.get('AudioTag'))
                 # TODO: add support for WVC1 and WMAP
-                if fourcc not in ('H264', 'AVC1', 'AACL', 'TTML'):
+                if fourcc not in ('H264', 'AVC1', 'AACL', 'TTML', 'EC-3'):
                     self.report_warning('%s is not a supported codec' % fourcc)
                     continue
                 tbr = int(track.attrib['Bitrate']) // 1000

yt_dlp/utils.py

@@ -3546,7 +3546,7 @@ def get_compatible_ext(*, vcodecs, acodecs, vexts, aexts, preferences=None):
     COMPATIBLE_CODECS = {
         'mp4': {
             'av1', 'hevc', 'avc1', 'mp4a',  # fourcc (m3u8, mpd)
-            'h264', 'aacl',  # Set in ISM
+            'h264', 'aacl', 'ec-3',  # Set in ISM
         },
         'webm': {
             'av1', 'vp9', 'vp8', 'opus', 'vrbs',