From 50eff38c1c071e2d389799843530c294d31887ed Mon Sep 17 00:00:00 2001
From: pukkandan <pukkandan.ytdlp@gmail.com>
Date: Thu, 23 Sep 2021 11:48:49 +0530
Subject: [PATCH] bugfix for a21e0ab1a1a03f82517cd8cec4b9a2b4d6b81ac3 Closes
 #1061

---
 yt_dlp/postprocessor/ffmpeg.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/yt_dlp/postprocessor/ffmpeg.py b/yt_dlp/postprocessor/ffmpeg.py
index 6f274b196..7ea01620e 100644
--- a/yt_dlp/postprocessor/ffmpeg.py
+++ b/yt_dlp/postprocessor/ffmpeg.py
@@ -730,11 +730,13 @@ class FFmpegMergerPP(FFmpegPostProcessor):
         filename = info['filepath']
         temp_filename = prepend_extension(filename, 'temp')
         args = ['-c', 'copy']
+        audio_streams = 0
         for (i, fmt) in enumerate(info['requested_formats']):
             if fmt.get('acodec') != 'none':
                 args.extend(['-map', f'{i}:a:0'])
                 if self.get_audio_codec(fmt['filepath']) == 'aac':
-                    args.extend([f'-bsf:{i}:a:0', 'aac_adtstoasc'])
+                    args.extend([f'-bsf:a:{audio_streams}', 'aac_adtstoasc'])
+                audio_streams += 1
             if fmt.get('vcodec') != 'none':
                 args.extend(['-map', '%u:v:0' % (i)])
         self.to_screen('Merging formats into "%s"' % filename)