Add support for “danmaku” subtitles on nicovideo.jp

[linkmauve]

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2017.08.06. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• [x] I've verified and I assure that I'm running youtube-dl 2017.08.06

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• [x] At least skimmed through the README, most notably the FAQ and BUGS sections
• [x] Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• [ ] Bug report (encountered problems with youtube-dl)
• [ ] Site support request (request for adding support for a new site)
• [x] Feature request (request for a new functionality)
• [ ] Question
• [ ] Other

---

If the purpose of this issue is a site support request please provide all kinds of example URLs support for which should be included (replace following example URLs by yours):

• Single video: http://nicovideo.jp/watch/sm10215922

---

Description of your issue, suggested solution and other information

Most videos on nicovideo.jp contain an XML file representing comments from users, meant to be rendered on top of the video in a similar way as subtitles.

youtube-dl should expose a way to retrieve this track, either to then convert it to ass, or to (be made available to video players](https://github.com/mpv-player/mpv/issues/4722).

[yan12125]

As a reference, for HTML5 videos, danmaku is served via a mysterious format from /api.json/

[
    {
        "ping": {
            "content": "rs:0"
        }
    },
    {
        "ping": {
            "content": "ps:0"
        }
    },
    {
        "thread": {
            "language": 1,
            "last_res": 1,
            "resultcode": 0,
            "revision": 1,
            "server_time": 1502041119,
            "thread": "1498481660",
            "ticket": "0x2e826693"
        }
    },
    {
        "leaf": {
            "count": 1,
            "language": 1,
            "thread": "1498481660"
        }
    },
    {
        "ping": {
            "content": "pf:0"
        }
    },
    {
        "ping": {
            "content": "ps:1"
        }
    },
    {
        "thread": {
            "language": 1,
            "last_res": 1,
            "resultcode": 0,
            "revision": 1,
            "server_time": 1502041119,
            "thread": "1498481660",
            "ticket": "0x2e826693"
        }
    },
    {
        "chat": {
            "anonymity": 1,
            "content": "给战姬打call，终于要出了",
            "date": 1498483144,
            "date_usec": 187515,
            "language": 1,
            "mail": "184",
            "no": 1,
            "premium": 1,
            "thread": "1498481660",
            "user_id": "7BSCuGwpjDFvigUQMAaMjC-q1WA",
            "vpos": 1402
        }
    },
    {
        "ping": {
            "content": "pf:1"
        }
    },
    {
        "ping": {
            "content": "ps:2"
        }
    },
    {
        "thread": {
            "fork": 1,
            "last_res": 1,
            "resultcode": 0,
            "revision": 1,
            "server_time": 1502041119,
            "thread": "1498481660",
            "ticket": "1500127358"
        }
    },
    {
        "global_num_res": {
            "num_res": 931,
            "thread": "1498481660"
        }
    },
    {
        "chat": {
            "content": "＠ジャンプ sm31574832",
            "date": 1500127358,
            "date_usec": 201000,
            "fork": 1,
            "no": 1,
            "thread": "1498481660",
            "vpos": 19800
        }
    },
    {
        "ping": {
            "content": "pf:2"
        }
    },
    {
        "ping": {
            "content": "rf:0"
        }
    }
]

This is captured from http://www.nicovideo.jp/watch/sm31464864.

[kayb94]

So the "chat" -> "content" is what is supposed to be the subtitle (I don't know japanese)?

"date" seems to be epoch, I mean seconds since 01/01/1970. It can be converted on command line e.g. by the following: > date --date='@1500127358' Sat Jul 15 16:02:38 CEST 2017

EDIT: At least I am not interested after seeing nicovideo requires login. ^^

[usushio]

Hi, I found a blog article that explains the various fields in the JSON file here (in Japanese): https://qiita.com/tor4kichi/items/74939b49954d3e72d789 Hopefully, it will be useful for this purpose.