Repository: youtube-dl
Issue: Problems on some techtalks.tv videos (but not all)
Labels: cant-reproduce

- [X] I've **verified** and **I assure** that I'm running youtube-dl **2017.07.15**

### Before submitting an *issue* make sure you have:
- [X] At least skimmed through [README](https://github.com/rg3/youtube-dl/blob/master/README.md) and **most notably** [FAQ](https://github.com/rg3/youtube-dl#faq) and [BUGS](https://github.com/rg3/youtube-dl#bugs) sections
- [X] [Searched](https://github.com/rg3/youtube-dl/search?type=Issues) the bugtracker for similar issues including closed ones

### What is the purpose of your *issue*?
- [X] Bug report (encountered problems with youtube-dl)
- [ ] Site support request (request for adding support for a new site)
- [ ] Feature request (request for a new functionality)
- [ ] Question
- [ ] Other

---

### If the purpose of this *issue* is a *bug report*, *site support request* or you are not completely sure provide the full verbose output:
```
$ youtube-dl -v http://techtalks.tv/talks/memory-networks-for-language-understanding/62356/
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'http://techtalks.tv/talks/memory-networks-for-language-understanding/62356/']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.07.15
[debug] Python version 2.7.13 - Darwin-16.6.0-x86_64-i386-64bit
[debug] exe versions: avconv 12, avprobe 12, ffmpeg 3.3.2, ffprobe 3.3.2, rtmpdump 2.4
[debug] Proxy map: {}
[TechTalks] 62356: Downloading webpage
[debug] Invoking downloader on u'rtmp://webcast.weyond.com/vod'
[download] Destination: Memory Networks for Language Understanding-62356.flv
[debug] rtmpdump command line: rtmpdump --verbose -r 'rtmp://webcast.weyond.com/vod' -o 'Memory Networks for Language Understanding-62356.flv.part' --playpath 'icml/2016/tutorials/mp4:tuts-crown-2' --resume --skip 1
[rtmpdump] RTMPDump v2.4
[rtmpdump] (c) 2010 Andrej Stepanchuk, Howard Chu, The Flvstreamer Team; license: GPL
[rtmpdump] DEBUG: Parsing...
[rtmpdump] DEBUG: Parsed protocol: 0
[rtmpdump] DEBUG: Parsed host    : webcast.weyond.com
[rtmpdump] DEBUG: Parsed app     : vod
[rtmpdump] DEBUG: Number of skipped key frames for resume: 1
[rtmpdump] DEBUG: Protocol : RTMP
[rtmpdump] DEBUG: Hostname : webcast.weyond.com
[rtmpdump] DEBUG: Port     : 1935
[rtmpdump] DEBUG: Playpath : icml/2016/tutorials/mp4:tuts-crown-2
[rtmpdump] DEBUG: tcUrl    : rtmp://webcast.weyond.com:1935/vod
[rtmpdump] DEBUG: app      : vod
[rtmpdump] DEBUG: live     : no
[rtmpdump] DEBUG: timeout  : 30 sec
[rtmpdump] DEBUG: Failed to get last keyframe.
[rtmpdump] DEBUG: Closing connection.
[rtmpdump] 0 bytes
[rtmpdump] RTMPDump v2.4
[rtmpdump] (c) 2010 Andrej Stepanchuk, Howard Chu, The Flvstreamer Team; license: GPL
[rtmpdump] DEBUG: Parsing...
[rtmpdump] DEBUG: Parsed protocol: 0
[rtmpdump] DEBUG: Parsed host    : webcast.weyond.com
[rtmpdump] DEBUG: Parsed app     : vod
[rtmpdump] DEBUG: Number of skipped key frames for resume: 1
[rtmpdump] DEBUG: Number of skipped key frames for resume: 1
[rtmpdump] DEBUG: Protocol : RTMP
[rtmpdump] DEBUG: Hostname : webcast.weyond.com
[rtmpdump] DEBUG: Port     : 1935
[rtmpdump] DEBUG: Playpath : icml/2016/tutorials/mp4:tuts-crown-2
[rtmpdump] DEBUG: tcUrl    : rtmp://webcast.weyond.com:1935/vod
[rtmpdump] DEBUG: app      : vod
[rtmpdump] DEBUG: live     : no
[rtmpdump] DEBUG: timeout  : 30 sec
[rtmpdump] DEBUG: Failed to get last keyframe.
[rtmpdump] DEBUG: Closing connection.


ERROR: rtmpdump exited with code 1
  File "/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/local/bin/youtube-dl/__main__.py", line 19, in <module>
    youtube_dl.main()
  File "/usr/local/bin/youtube-dl/youtube_dl/__init__.py", line 465, in main
    _real_main(argv)
  File "/usr/local/bin/youtube-dl/youtube_dl/__init__.py", line 455, in _real_main
    retcode = ydl.download(all_urls)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1941, in download
    url, force_generic_extractor=self.params.get('force_generic_extractor', False))
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 787, in extract_info
    return self.process_ie_result(ie_result, download, extra_info)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 841, in process_ie_result
    return self.process_video_result(ie_result, download=download)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1584, in process_video_result
    self.process_info(new_info)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1848, in process_info
    success = dl(filename, info_dict)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1790, in dl
    return fd.download(name, info)
  File "/usr/local/bin/youtube-dl/youtube_dl/downloader/common.py", line 361, in download
    return self.real_download(filename, info_dict)
  File "/usr/local/bin/youtube-dl/youtube_dl/downloader/rtmp.py", line 202, in real_download
    self.report_error('rtmpdump exited with code %d' % retval)
  File "/usr/local/bin/youtube-dl/youtube_dl/downloader/common.py", line 163, in report_error
    self.ydl.report_error(*args, **kargs)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 604, in report_error
    self.trouble(error_message, tb)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 566, in trouble
    tb_data = traceback.format_list(traceback.extract_stack())



```
---

### Description of your *issue*, suggested solution and other information

I'm trying to download a video from techtalks.tv with the above command, which fails. Looking through the existing issues related to techtalks.tv, I found [another issue](https://github.com/rg3/youtube-dl/issues/11448). The link mentioned in that issue does not fail, I can download that video without problems. So I think the problem isn't in my rtmpdump installation.