[ffmpeg] Detect libavformat version for `aac_adtstoasc`

and print available features in verbose head
Based on https://github.com/ytdl-org/youtube-dl/pull/29581

yt_dlp/YoutubeDL.py

@@ -3350,7 +3350,11 @@ class YoutubeDL(object):
             platform.architecture()[0],
             platform_name()))
 
-        exe_versions = FFmpegPostProcessor.get_versions(self)
+        exe_versions, ffmpeg_features = FFmpegPostProcessor.get_versions_and_features(self)
+        ffmpeg_features = {key for key, val in ffmpeg_features.items() if val}
+        if ffmpeg_features:
+            exe_versions['ffmpeg'] += f' (%s)' % ','.join(ffmpeg_features)
+
         exe_versions['rtmpdump'] = rtmpdump_version()
         exe_versions['phantomjs'] = PhantomJSwrapper._version()
         exe_str = ', '.join(

yt_dlp/downloader/external.py

@@ -21,7 +21,6 @@ from ..utils import (
     encodeArgument,
     handle_youtubedl_headers,
     check_executable,
-    is_outdated_version,
     Popen,
     sanitize_open,
 )
@@ -459,7 +458,7 @@ class FFmpegFD(ExternalFD):
                 args += ['-f', 'mpegts']
             else:
                 args += ['-f', 'mp4']
-                if (ffpp.basename == 'ffmpeg' and is_outdated_version(ffpp._versions['ffmpeg'], '3.2', False)) and (not info_dict.get('acodec') or info_dict['acodec'].split('.')[0] in ('aac', 'mp4a')):
+                if (ffpp.basename == 'ffmpeg' and ffpp._features.get('needs_adtstoasc')) and (not info_dict.get('acodec') or info_dict['acodec'].split('.')[0] in ('aac', 'mp4a')):
                     args += ['-bsf:a', 'aac_adtstoasc']
         elif protocol == 'rtmp':
             args += ['-f', 'flv']

yt_dlp/postprocessor/ffmpeg.py

@@ -75,9 +75,14 @@ class FFmpegPostProcessor(PostProcessor):
                 self.basename, self.basename, required_version)
             self.report_warning(warning)
 
+    @staticmethod
+    def get_versions_and_features(downloader=None):
+        pp = FFmpegPostProcessor(downloader)
+        return pp._versions, pp._features
+
     @staticmethod
     def get_versions(downloader=None):
-        return FFmpegPostProcessor(downloader)._versions
+        return FFmpegPostProcessor.get_version_and_features(downloader)[0]
 
     def _determine_executables(self):
         programs = ['avprobe', 'avconv', 'ffmpeg', 'ffprobe']
@@ -99,9 +104,12 @@ class FFmpegPostProcessor(PostProcessor):
             if prog != 'ffmpeg' or not out:
                 return
 
+            mobj = re.search(r'(?m)^\s+libavformat\s+(?:[0-9. ]+)\s+/\s+(?P<runtime>[0-9. ]+)', out)
+            lavf_runtime_version = mobj.group('runtime').replace(' ', '') if mobj else None
             self._features = {
                 'fdk': '--enable-libfdk-aac' in out,
                 'setts': 'setts' in out.splitlines(),
+                'needs_adtstoasc': is_outdated_version(lavf_runtime_version, '57.56.100', False),
             }
 
         self.basename = None