ニコ動HTML5プレイヤーページの動画内部データJSONの例

#js-initial-watch-data.json

{
	"video": {
		"id": "sm13924244",
		"title": "【ポポポポーン】あいさつするたび速度落ちるね【シーク禁止】",
		"originalTitle": "【ポポポポーン】あいさつするたび速度落ちるね【シーク禁止】",
		"description": "ポポポポーン教信者なら余裕だよな？　　　　加速:<a href=\"https:\/\/www.nicovideo.jp\/watch\/sm13924147\" class=\"watch\">sm13924147<\/a>　ピッチアップ:<a href=\"https:\/\/www.nicovideo.jp\/watch\/sm13941513\" class=\"watch\">sm13941513<\/a> ピッチダウン:<a href=\"https:\/\/www.nicovideo.jp\/watch\/sm13941810\" class=\"watch\">sm13941810<\/a> あいさつするたび〇〇【<a href=\"https:\/\/www.nicovideo.jp\/mylist\/24558006\" target=\"_blank\" rel=\"noopener\">mylist\/24558006<\/a>】          移動順　加速→ピッチアップ→減速→ピッチダウン→加速（以下ry　無限ループってこわくね？",
		"originalDescription": "ポポポポーン教信者なら余裕だよな？　　　　加速:sm13924147　ピッチアップ:sm13941513 ピッチダウン:sm13941810 あいさつするたび〇〇【mylist\/24558006】          移動順　加速→ピッチアップ→減速→ピッチダウン→加速（以下ry　無限ループってこわくね？",
		"thumbnailURL": "https:\/\/tn.smilevideo.jp\/smile?i=13924244",
		"largeThumbnailURL": null,
		"postedDateTime": "2011\/03\/22 02:18:29",
		"originalPostedDateTime": null,
		"width": null,
		"height": null,
		"duration": 610,
		"viewCount": 46440,
		"mylistCount": 289,
		"translation": false,
		"translator": null,
		"movieType": "mp4",
		"badges": null,
		"mainCommunityId": null,
		"dmcInfo": null,
		"backCommentType": null,
		"channelId": null,
		"isCommentExpired": false,
		"isWide": null,
		"isOfficialAnime": null,
		"isNoBanner": null,
		"isDeleted": false,
		"isTranslated": false,
		"isR18": false,
		"isAdult": false,
		"isNicowari": null,
		"isPublic": true,
		"isPublishedNicoscript": null,
		"isNoNGS": null,
		"isCommunityMemberOnly": "",
		"isCommonsTreeExists": null,
		"isNoIchiba": false,
		"isOfficial": false,
		"isMonetized": false,
		"smileInfo": {
			"url": "https:\/\/smile-cls31.sl.nicovideo.jp\/smile?m=13924244.77128low",
			"isSlowLine": false,
			"currentQualityId": "auto",
			"qualityIds": ["auto", "low"]
		}
	},
	"player": {
		"playerInfoXMLUpdateTIme": 1532318603,
		"isContinuous": false
	},
	"thread": {
		"commentCount": 13472,
		"hasOwnerThread": "1",
		"mymemoryLanguage": null,
		"serverUrl": "https:\/\/nmsg.nicovideo.jp\/api\/",
		"subServerUrl": "https:\/\/nmsg.nicovideo.jp\/api\/",
		"ids": {
			"default": "1300727909",
			"nicos": null,
			"community": null
		}
	},
	"commentComposite": {
		"threads": [{
			"id": 1300727909,
			"fork": 1,
			"isActive": true,
			"postkeyStatus": 0,
			"isDefaultPostTarget": false,
			"isThreadkeyRequired": false,
			"isLeafRequired": false,
			"label": "owner",
			"isOwnerThread": true,
			"hasNicoscript": true
		}, {
			"id": 1300727909,
			"fork": 0,
			"isActive": true,
			"postkeyStatus": 0,
			"isDefaultPostTarget": true,
			"isThreadkeyRequired": false,
			"isLeafRequired": true,
			"label": "default",
			"isOwnerThread": false,
			"hasNicoscript": false
		}],
		"layers": [{
			"index": 0,
			"isTranslucent": false,
			"threadIds": [{
				"id": 1300727909,
				"fork": 1
			}]
		}, {
			"index": 1,
			"isTranslucent": false,
			"threadIds": [{
				"id": 1300727909,
				"fork": 0
			}]
		}]
	},
	"tags": [{
		"id": "111625184",
		"name": "エンターテイメント",
		"isCategory": true,
		"isCategoryCandidate": true,
		"isDictionaryExists": true,
		"isLocked": true
	}, {
		"id": "111669041",
		"name": "言ったら減速してしまうシリーズ",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "111827268",
		"name": "あいさつの魔法。",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "114004558",
		"name": "シーク禁止",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "161227210",
		"name": "お使いのPCは正常です",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "198088133",
		"name": "腹筋崩壊",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "204074040",
		"name": "ポポポポーン教",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "220209063",
		"name": "ヘリコプター",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "259588404",
		"name": "ノイズミュージック",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "269292101",
		"name": "音量注意",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}, {
		"id": "271320885",
		"name": "睡眠用BGM",
		"isCategory": false,
		"isCategoryCandidate": false,
		"isDictionaryExists": true,
		"isLocked": false
	}],
	"playlist": {
		"watchId": "sm13924244",
		"referer": "https:\/\/www.nicovideo.jp\/search\/%E3%82%B7%E3%83%BC%E3%82%AF%E7%A6%81%E6%AD%A2?ref=nicotop_search",
		"parameter": null,
		"recipe": "eyJpZCI6InZpZGVvX3BsYXlsaXN0X3NlYXJjaF9jb250aW51b3VzIiwic2VhcmNoUXVlcnkiOnsidHlwZSI6ImtleXdvcmQiLCJxdWVyeSI6IuOCt-ODvOOCr-emgeatoiIsInBhZ2UiOjEsInBlclBhZ2UiOjMyLCJzb3J0IjoiK3AifX0"
	},
	"owner": {
		"id": "18989070",
		"nickname": "物理研究愛好会 さん",
		"iconURL": "https:\/\/secure-dcdn.cdn.nimg.jp\/nicoaccount\/usericon\/1898\/18989070.jpg?1289674641",
		"nicoliveInfo": null,
		"channelInfo": null,
		"isUserVideoPublic": true,
		"isUserMyVideoPublic": false,
		"isUserOpenListPublic": true
	},
	"viewer": {
		"id": 53842185,
		"nickname": "tor4kichi さん",
		"prefecture": 23,
		"sex": 0,
		"age": 29,
		"isPremium": false,
		"isPostLocked": false,
		"isHtrzm": false,
		"isTwitterConnection": false,
		"nicosid": "1518132923.1546675337"
	},
	"community": null,
	"mainCommunity": null,
	"channel": null,
	"ad": {
		"vastMetaData": null
	},
	"lead": {
		"tagRelatedMarquee": null,
		"tagRelatedBanner": null,
		"videoEndBannerIn": null,
		"videoEndOverlay": null
	},
	"maintenance": null,
	"context": {
		"playFrom": null,
		"initialPlaybackPosition": null,
		"initialPlaybackType": null,
		"playLength": null,
		"returnId": null,
		"returnTo": null,
		"returnMsg": null,
		"watchId": "sm13924244",
		"isNoMovie": null,
		"isNoRelatedVideo": null,
		"isDownloadCompleteWait": null,
		"isNoNicotic": null,
		"isNeedPayment": false,
		"isAdultRatingNG": false,
		"isPlayable": null,
		"isTranslatable": false,
		"isTagUneditable": false,
		"isVideoOwner": false,
		"isThreadOwner": false,
		"isOwnerThreadEditable": null,
		"useChecklistCache": null,
		"isDisabledMarquee": null,
		"isDictionaryDisplayable": true,
		"isDefaultCommentInvisible": false,
		"accessFrom": null,
		"csrfToken": "53842185-1542627809-84dc37065d2ddade2d774cb9509b4ecdbff3fedd",
		"translationVersionJsonUpdateTime": 1509423100,
		"userkey": "1542543208.~1~gNdO9DobwaQ4nJEH-KM_EjPdGTQivB11xEcIKXRDMJ0",
		"watchAuthKey": "1:1542541408:1300727909:90c4e09186644bd94f1c069f663188944d5701fc097d585bd128d95d6dfd1cef",
		"watchTrackId": "uH4u9qxJWy_1542541408965",
		"watchPageServerTime": 1542541409071,
		"isAuthenticationRequired": false,
		"isPeakTime": true,
		"ngRevision": 5,
		"categoryName": "エンターテイメント",
		"categoryKey": "ent",
		"categoryGroupName": "エンタメ・音楽",
		"categoryGroupKey": "g_ent2",
		"yesterdayRank": null,
		"highestRank": 170,
		"isMyMemory": false,
		"ownerNGList": [{
			"source": "",
			"destination": ""
		}],
		"linkedChannelVideos": null,
		"isAllowEmbedPlayer": true
	},
	"liveTopics": {
		"items": [{
			"id": "lv316930944",
			"title": "【艦これ6-4ラスト】んんｗｗｗ主砲ガン積み以外ありえないｗｗｗｗｗｗｗ",
			"thumbnailURL": "https:\/\/secure-dcdn.cdn.nimg.jp\/comch\/community-icon\/64x64\/co3685734.jpg?1531753439",
			"point": 90,
			"isHigh": false,
			"elapsedTimeM": 42,
			"communityId": "co3685734",
			"communityName": "ちゃらんぽらんの集会所"
		}, {
			"id": "lv316824917",
			"title": "【せーのポチ枠】機動戦士ガンダムSEED DESTINY  1〜8話観てみるく♡",
			"thumbnailURL": "https:\/\/secure-dcdn.cdn.nimg.jp\/comch\/community-icon\/64x64\/co1921730.jpg?1535652009",
			"point": 85,
			"isHigh": false,
			"elapsedTimeM": 42,
			"communityId": "co1921730",
			"communityName": "ミルクとクルミとモモコ"
		}]
	}
}

video.commentCompositeが追加されていたようで、これを使うとスムーズに http://nmsg.nicovideo.jp/api.json/ でのコメント取得や投稿をコントロールできると思います。