Update parsing of storyboards

[benob]

The format for getting storyboards seems to have changed. They are now available in the 'player_response' field.

I checked with master@rg3/youtube-dl that it works.

[MarcAbonce]

Hi. Sorry for the delay.
It looks like YouTube changed the way they return storyboard urls again. When I try to run your branch, I get an error because the storyboards are not found in player_response either.

[benob]

After investigation, it only seems to work for a subset of videos.

• Example of working video: X5oD_thIk3c
• Example of non-working video: Iytbx7IGKCM
  It fails if 'storyboards' is not in player_response at line 1514 but fixing that doesn't get storyboards from the non-working videos.

I also get better results for the non-working video when applying my patch to master but still no storyboards.

I can't find the jpeg filenames in the downloaded data, but maybe I am looking at the wrong place. Do you have ideas?

[MarcAbonce]

You were right.
For the videos where it failed, I found that when the storyboards are not in player_response, you can still find them in a script inside the web page itself.
Now this should work with all videos.
Thank you so much!