Including feature to increase or decrease media (volume) audio level

README.md

@@ -361,6 +361,9 @@ which means you can modify it, redistribute it or use it however you like.
                                      a value between 0 (better) and 9 (worse)
                                      for VBR or a specific bitrate like 128K
                                      (default 5)
+    --audio-volume VOLUME            Specify ffmpeg/avconv audio volume, insert 
+				     a value in dB to increase audio volume.
+                                     (default 4)
     --recode-video FORMAT            Encode the video to another format if
                                      necessary (currently supported:
                                      mp4|flv|ogg|webm|mkv|avi)

youtube_dl/__init__.py

@@ -168,6 +168,11 @@ def _real_main(argv=None):
         opts.audioquality = opts.audioquality.strip('k').strip('K')
         if not opts.audioquality.isdigit():
             parser.error('invalid audio quality specified')
+
+    if opts.audiovolume:
+        if not opts.audioquality.isdigit():
+            parser.error('invalid audio volume specified')
+
     if opts.recodevideo is not None:
         if opts.recodevideo not in ['mp4', 'flv', 'webm', 'ogg', 'mkv', 'avi']:
             parser.error('invalid video recode format specified')
@@ -221,6 +226,7 @@ def _real_main(argv=None):
             'key': 'FFmpegExtractAudio',
             'preferredcodec': opts.audioformat,
             'preferredquality': opts.audioquality,
+            'preferredvolume': opts.audiovolume,
             'nopostoverwrites': opts.nopostoverwrites,
         })
     if opts.recodevideo:
@@ -377,7 +383,7 @@ def _real_main(argv=None):
     with YoutubeDL(ydl_opts) as ydl:
         # Update version
         if opts.update_self:
-            update_self(ydl.to_screen, opts.verbose, ydl._opener)
+            update_self(ydl.to_screen, opts.verbose)
 
         # Remove cache dir
         if opts.rm_cachedir:

youtube_dl/options.py

@@ -688,6 +688,12 @@ def parseOpts(overrideArguments=None):
         '--audio-quality', metavar='QUALITY',
         dest='audioquality', default='5',
         help='Specify ffmpeg/avconv audio quality, insert a value between 0 (better) and 9 (worse) for VBR or a specific bitrate like 128K (default %default)')
+
+    postproc.add_option(
+        '--audio-volume', metavar='QUALITY',
+        dest='audiovolume', default=None,
+        help='Specify ffmpeg/avconv audio volume, insert a value in dB to increase audio volume (default %default)')
+
     postproc.add_option(
         '--recode-video',
         metavar='FORMAT', dest='recodevideo', default=None,

youtube_dl/postprocessor/ffmpeg.py

@@ -166,12 +166,13 @@ class FFmpegPostProcessor(PostProcessor):
 
 
 class FFmpegExtractAudioPP(FFmpegPostProcessor):
-    def __init__(self, downloader=None, preferredcodec=None, preferredquality=None, nopostoverwrites=False):
+    def __init__(self, downloader=None, preferredcodec=None, preferredquality=None, preferredvolume=None, nopostoverwrites=False):
         FFmpegPostProcessor.__init__(self, downloader)
         if preferredcodec is None:
             preferredcodec = 'best'
         self._preferredcodec = preferredcodec
         self._preferredquality = preferredquality
+        self._preferredvolume = preferredvolume
         self._nopostoverwrites = nopostoverwrites
 
     def get_audio_codec(self, path):
@@ -242,6 +243,8 @@ class FFmpegExtractAudioPP(FFmpegPostProcessor):
                         more_opts += ['-q:a', self._preferredquality]
                     else:
                         more_opts += ['-b:a', self._preferredquality + 'k']
+                if self._preferredvolume is not None:
+                    more_opts += ['-af', 'volume=volume='+self._preferredvolume+'dB:precision=fixed']
         else:
             # We convert the audio (lossy)
             acodec = {'mp3': 'libmp3lame', 'aac': 'aac', 'm4a': 'aac', 'opus': 'opus', 'vorbis': 'libvorbis', 'wav': None}[self._preferredcodec]
@@ -253,6 +256,10 @@ class FFmpegExtractAudioPP(FFmpegPostProcessor):
                     more_opts += ['-q:a', self._preferredquality]
                 else:
                     more_opts += ['-b:a', self._preferredquality + 'k']
+
+            if self._preferredvolume is not None:
+                more_opts += ['-af', 'volume=volume='+self._preferredvolume+'dB:precision=fixed']
+
             if self._preferredcodec == 'aac':
                 more_opts += ['-f', 'adts']
             if self._preferredcodec == 'm4a':