Unable to download some YouTube videos with iPhone User Agent.

[koji2100]

Unable to download some YouTube videos that needs encrypted signature, with iPhone User Agent.

youtube-dl.exe --user-agent "Mozilla/5.0 (iPad; CPU OS 6_0 like Mac OS X) Ap
pleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A403 Safari/8536.25" --verbose -f mp4 http
://www.youtube.com/watch?v=2jTg-q6Drt0
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['--user-agent', 'Mozilla/5.0 (iPad; CPU OS 6_0 like Mac OS X) AppleWebKi
t/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A403 Safari/8536.25', '--verbose', '-f', 'mp4', 'h
ttp://www.youtube.com/watch?v=2jTg-q6Drt0']
[debug] youtube-dl version 2013.09.17
[debug] Python version 2.7.5 - Windows-7-6.1.7601-SP1
[debug] Proxy map: {}
[youtube] Setting language
[youtube] 2jTg-q6Drt0: Downloading video webpage
[youtube] 2jTg-q6Drt0: Downloading video info webpage
[youtube] 2jTg-q6Drt0: Extracting video information
WARNING: unable to extract uploader nickname
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 46, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 37, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 45, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 22, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 44, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 35, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 43, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 34, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 18, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 5, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 36, html5 player None
WARNING: unable to extract html5 player; please report this issue on http://yt-dl.org/bug
[youtube] encrypted signature length 85 (42.42), itag 17, html5 player None
ERROR: unable to download video
Traceback (most recent call last):
File "youtube_dl\YoutubeDL.pyo", line 571, in download
File "youtube_dl\YoutubeDL.pyo", line 336, in extract_info
File "youtube_dl\YoutubeDL.pyo", line 419, in process_ie_result
File "youtube_dl\YoutubeDL.pyo", line 366, in process_ie_result
File "youtube_dl\YoutubeDL.pyo", line 548, in process_info
UnavailableVideoError: HTTP Error 403: Forbidden

example:
http://www.youtube.com/watch?v=2jTg-q6Drt0
http://www.youtube.com/watch?v=NhI2mp-WIck
http://www.youtube.com/watch?v=RfBHVbo543o
http://www.youtube.com/watch?v=cr8magEp0Ho

[jaimeMF]

Yooutube serves a different page if it's a mobile device, the most important difference is that it doesn't include the ytplayer.config. Therefore youtube-dl tries to use the signatures from the /get_video_info page, which can't be used (I think it doesn't use the same algo).
You'll need to use another UA, adding support for using the signatures from /get_video_info would require more work than with the current system, and I don't know if it could be automated.