Format 171 is 128k vorbis audio, while youtube-dl says it's 48k

[aykevl]

I avoided format 171 because according to youtube-dl it's a low-quality 48kbps format, but I found out (via Wikipedia) that it has a much higher bitrate (128kbps):
http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs
I downloaded both formats of the same video. ffprobe said they were both 128kbps, and the filesize was also similar. So I guess youtube-dl somehow doesn't display the format properly.

$ youtube-dl -F https://www.youtube.com/watch?v=TK4u6wm-HIk
[youtube] Setting language
[youtube] TK4u6wm-HIk: Downloading webpage
[youtube] TK4u6wm-HIk: Downloading video info webpage
[youtube] TK4u6wm-HIk: Extracting video information
[info] Available formats for TK4u6wm-HIk:
format code extension resolution  note 
171         webm      audio only  DASH audio , audio@ 48k (worst)
140         m4a       audio only  DASH audio , audio@128k
160         mp4       144p        DASH video , video only
242         webm      240p        DASH video , video only
133         mp4       240p        DASH video , video only
243         webm      360p        DASH video , video only
134         mp4       360p        DASH video , video only
244         webm      480p        DASH video , video only
135         mp4       480p        DASH video , video only
247         webm      720p        DASH video , video only
136         mp4       720p        DASH video , video only
248         webm      1080p       DASH video , video only
137         mp4       1080p       DASH video , video only
17          3gp       176x144     
36          3gp       320x240     
5           flv       400x240     
43          webm      640x360     
18          mp4       640x360     
22          mp4       1280x720    (best)

[juancri]

I think you're right. I get these results:

Format 171 (webm): 104 kb/s
Fromat 140 (m4a): 127 kb/s

[phihag]

Thank you for the report, fixed.

[aykevl]

Thank you for fixing it!