YouTube Video Manager – Locate Edit Subtitle Option

Currently you cannot add a subtitle/caption track to someone else's video.

However, you can prepare the caption/subtitle file for the video and then share it the author so they can add it to the video (it's simple and I don't think he or she would object since subtitles do not have to be turned on by default).

Since it will be in another language as the video's audio track (and not in English either) you will have to prepare a time-coded subtitle script (or caption file). There are a number of articles about that available online including a good one to start with on Youtube help site.

Overall guidelines on preparing and adding subtitles to Youtube are available here.

Assuming you have Python installed, you can use getyoutubecc, which is a Python script.

Execution is as follows

>> python getyoutubecc Akqkvx407c8

Then keep the video and .srt in the same folder and you should be able to play in VLC.

For a non-technical way try one of the conversion sites such as http://mo.dbxdb.com/, which will download the .srt within a zip.

Select the track from the zip file

And then you should see the subtitles appear

For videos with multiple tracks you will have to dig in and save it from .xml to .srt manually, there isn't a ready made tool out there on the web

http://video.google.com/timedtext?lang=<LANG>&v=<VIDEOID>

Where can be en for English, it for Italian and de for German.
<VIDEOID> is the id of your Youtube video.

For some videos, it appears necessary to specify the name of the subtitle track, as seen on the Youtube page of the video, as a third argument:

http://video.google.com/timedtext?lang=<LANG>&v=<VIDEOID>&name=<NAME>