chore(main): release 6.4.1 (#507)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -1,5 +1,19 @@
 # Changelog
 
+## [6.4.1](https://github.com/LuanRT/YouTube.js/compare/v6.4.0...v6.4.1) (2023-10-02)
+
+
+### Bug Fixes
+
+* **Feed:** Do not throw when multiple continuations are present ([8e372d5](https://github.com/LuanRT/YouTube.js/commit/8e372d5c67f148be288bb0485f2c70ec43fbecd0))
+* **Playlist:** Throw a more helpful error when parsing empty responses ([987f506](https://github.com/LuanRT/YouTube.js/commit/987f50604a0163f9a07091ce787995c6f6fddb75))
+
+
+### Performance Improvements
+
+* Cache deciphered n-params by info response ([#505](https://github.com/LuanRT/YouTube.js/issues/505)) ([d2959b3](https://github.com/LuanRT/YouTube.js/commit/d2959b3a55a5081295da4754627913933bbaf1e7))
+* **generator:** Remove duplicate checks in `isMiscType` ([#506](https://github.com/LuanRT/YouTube.js/issues/506)) ([68df321](https://github.com/LuanRT/YouTube.js/commit/68df3218580db10c9a0932c93ff2ce487526ff1e))
+
 ## [6.4.0](https://github.com/LuanRT/YouTube.js/compare/v6.3.0...v6.4.0) (2023-09-10)
 
 

README.md

@@ -325,6 +325,9 @@ Retrieves video info.
 - `<info>#download(options)`
   - Downloads the video. See [download](#download).
 
+- `<info>#getTranscript()`
+  - Retrieves the video's transcript.
+
 - `<info>#filters`
   - Returns filters that can be applied to the watch next feed.
 
@@ -660,16 +663,6 @@ console.info('Playback url:', url);
 | video_id | `string` | Video id |
 | options | `FormatOptions` | Format options |
 
-<a name="gettranscript"></a>
-### `getTranscript(video_id)`
-Retrieves a given video's transcript.
-
-**Returns**: `Promise<Transcript>`
-
-| Param | Type | Description |
-| --- | --- | --- |
-| video_id | `string` | Video id |
-
 <a name="download"></a>
 ### `download(video_id, options?)`
 Downloads a given video.

docs/updating-the-parser.md

@@ -31,24 +31,22 @@ For example, suppose we have found a new renderer named `verticalListRenderer`.
 > `../classes/VerticalList.ts`
 
 ```ts
-import Parser from '..';
-import { YTNode } from '../helpers';
-import type { RawNode } from '../index.js';
+import Parser, { RawNode } from '../index.js';
+import { YTNode } from '../helpers.js';
 
-class VerticalList extends YTNode {
+export default class VerticalList extends YTNode {
   static type = 'VerticalList';
 
   header;
   contents;
 
   constructor(data: RawNode) {
+    super();
     // parse the data here, ex;
     this.header = Parser.parseItem(data.header);
     this.contents = Parser.parseArray(data.contents);
   }
 }
-
-export default VerticalList;
 ```
 
 You may use the parser's generated class for the new renderer as a starting point for your own implementation.

examples/auth/index.js

@@ -1,4 +1,4 @@
-const { Innertube, UniversalCache } = require('youtubei.js');
+import { Innertube, UniversalCache } from  'youtubei.js';
 
 (async () => {
   const yt = await Innertube.create({

examples/transcript/index.ts

@@ -0,0 +1,16 @@
+import { Innertube } from 'youtubei.js';
+
+(async () => {
+  const yt = await Innertube.create({ generate_session_locally: true });
+
+  const info = await yt.getInfo('hePb00CqvP0');
+
+  const defaultTranscriptInfo = await info.getTranscript();
+
+  console.log(`Got ${defaultTranscriptInfo.selectedLanguage} transcript with ${defaultTranscriptInfo.transcript.content.body.initial_segments.length} lines.`);
+
+  console.log("Fetching Hebrew transcript...");
+
+  const heTranscriptInfo = await defaultTranscriptInfo.selectLanguage('Hebrew');
+  console.log(`Got ${heTranscriptInfo.selectedLanguage} transcript with ${heTranscriptInfo.transcript.content.body.initial_segments.length} lines.`);
+})();

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "youtubei.js",
-  "version": "6.4.0",
+  "version": "6.4.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "youtubei.js",
-      "version": "6.4.0",
+      "version": "6.4.1",
       "funding": [
         "https://github.com/sponsors/LuanRT"
       ],

package.json

@@ -1,6 +1,6 @@
 {
   "name": "youtubei.js",
-  "version": "6.4.0",
+  "version": "6.4.1",
   "description": "A wrapper around YouTube's private API. Supports YouTube, YouTube Music, YouTube Kids and YouTube Studio (WIP).",
   "type": "module",
   "types": "./dist/src/platform/lib.d.ts",

src/Innertube.ts

@@ -14,8 +14,6 @@ import NotificationsMenu from './parser/youtube/NotificationsMenu.js';
 import Playlist from './parser/youtube/Playlist.js';
 import Search from './parser/youtube/Search.js';
 import VideoInfo from './parser/youtube/VideoInfo.js';
-import ContinuationItem from './parser/classes/ContinuationItem.js';
-import Transcript from './parser/classes/Transcript.js';
 
 import { Kids, Music, Studio } from './core/clients/index.js';
 import { AccountManager, InteractionManager, PlaylistManager } from './core/managers/index.js';
@@ -38,7 +36,7 @@ import {
 import { GetUnseenCountEndpoint } from './core/endpoints/notification/index.js';
 
 import type { ApiResponse } from './core/Actions.js';
-import { type IGetTranscriptResponse, type IBrowseResponse, type IParsedResponse } from './parser/types/index.js';
+import { type IBrowseResponse, type IParsedResponse } from './parser/types/index.js';
 import type { INextRequest } from './types/index.js';
 import type { DownloadOptions, FormatOptions } from './types/FormatUtils.js';
 
@@ -334,35 +332,6 @@ export default class Innertube {
     return info.chooseFormat(options);
   }
 
-  /**
-   * Retrieves a video's transcript.
-   * @param video_id - The video id.
-   */
-  async getTranscript(video_id: string): Promise<Transcript> {
-    throwIfMissing({ video_id });
-
-    const next_response = await this.actions.execute(NextEndpoint.PATH, { ...NextEndpoint.build({ video_id }), parse: true });
-
-    if (!next_response.engagement_panels)
-      throw new InnertubeError('Engagement panels not found. Video likely has no transcript.');
-
-    const transcript_panel = next_response.engagement_panels.get({
-      panel_identifier: 'engagement-panel-searchable-transcript'
-    });
-
-    if (!transcript_panel)
-      throw new InnertubeError('Transcript panel not found. Video likely has no transcript.');
-
-    const transcript_continuation = transcript_panel.content?.as(ContinuationItem);
-
-    if (!transcript_continuation)
-      throw new InnertubeError('Transcript continuation not found.');
-
-    const transcript_response = await transcript_continuation.endpoint.call<IGetTranscriptResponse>(this.actions, { parse: true });
-
-    return transcript_response.actions_memo.getType(Transcript).first();
-  }
-
   /**
    * Downloads a given video. If you only need the direct download link see {@link getStreamingData}.
    * If you wish to retrieve the video info too, have a look at {@link getBasicInfo} or {@link getInfo}.

src/core/Player.ts

@@ -10,6 +10,7 @@ import type { FetchFunction } from '../types/PlatformShim.js';
  */
 export default class Player {
   #nsig_sc;
+  #nsig_cache;
   #sig_sc;
   #sig_sc_timestamp;
   #player_id;
@@ -21,6 +22,8 @@ export default class Player {
     this.#sig_sc_timestamp = signature_timestamp;
 
     this.#player_id = player_id;
+
+    this.#nsig_cache = new Map<string, string>();
   }
 
   static async create(cache: ICache | undefined, fetch: FetchFunction = Platform.shim.fetch): Promise<Player> {
@@ -66,7 +69,7 @@ export default class Player {
     return await Player.fromSource(cache, sig_timestamp, sig_sc, nsig_sc, player_id);
   }
 
-  decipher(url?: string, signature_cipher?: string, cipher?: string): string {
+  decipher(url?: string, signature_cipher?: string, cipher?: string, this_response_nsig_cache?: Map<string, string>): string {
     url = url || signature_cipher || cipher;
 
     if (!url)
@@ -93,15 +96,23 @@ export default class Player {
     const n = url_components.searchParams.get('n');
 
     if (n) {
-      const nsig = Platform.shim.eval(this.#nsig_sc, {
-        nsig: n
-      });
+      let nsig;
 
-      if (typeof nsig !== 'string')
-        throw new PlayerError('Failed to decipher nsig');
+      if (this_response_nsig_cache && this_response_nsig_cache.has(n)) {
+        nsig = this_response_nsig_cache.get(n) as string;
+      } else {
+        nsig = Platform.shim.eval(this.#nsig_sc, {
+          nsig: n
+        });
 
-      if (nsig.startsWith('enhanced_except_')) {
-        console.warn('Warning:\nCould not transform nsig, download may be throttled.\nChanging the InnerTube client to "ANDROID" might help!');
+        if (typeof nsig !== 'string')
+          throw new PlayerError('Failed to decipher nsig');
+
+        if (nsig.startsWith('enhanced_except_')) {
+          console.warn('Warning:\nCould not transform nsig, download may be throttled.\nChanging the InnerTube client to "ANDROID" might help!');
+        } else if (this_response_nsig_cache) {
+          this_response_nsig_cache.set(n, nsig);
+        }
       }
 
       url_components.searchParams.set('n', nsig);

src/core/mixins/Feed.ts

@@ -185,10 +185,8 @@ export default class Feed<T extends IParsedResponse = IParsedResponse> {
    */
   async getContinuationData(): Promise<T | undefined> {
     if (this.#continuation) {
-      if (this.#continuation.length > 1)
-        throw new InnertubeError('There are too many continuations, you\'ll need to find the correct one yourself in this.page');
       if (this.#continuation.length === 0)
-        throw new InnertubeError('There are no continuations');
+        throw new InnertubeError('There are no continuations.');
 
       const response = await this.#continuation[0].endpoint.call<T>(this.#actions, { parse: true });
 

src/core/mixins/MediaInfo.ts

@@ -10,6 +10,8 @@ import Parser from '../../parser/index.js';
 import type { DashOptions } from '../../types/DashOptions.js';
 import PlayerStoryboardSpec from '../../parser/classes/PlayerStoryboardSpec.js';
 import { getStreamingInfo } from '../../utils/StreamingInfo.js';
+import ContinuationItem from '../../parser/classes/ContinuationItem.js';
+import TranscriptInfo from '../../parser/youtube/TranscriptInfo.js';
 
 export default class MediaInfo {
   #page: [IPlayerResponse, INextResponse?];
@@ -84,6 +86,36 @@ export default class MediaInfo {
     return FormatUtils.download(options, this.#actions, this.playability_status, this.streaming_data, this.#actions.session.player, this.cpn);
   }
 
+  /**
+   * Retrieves the video's transcript.
+   * @param video_id - The video id.
+   */
+  async getTranscript(): Promise<TranscriptInfo> {
+    const next_response = this.page[1];
+
+    if (!next_response)
+      throw new InnertubeError('Cannot get transcript from basic video info.');
+
+    if (!next_response.engagement_panels)
+      throw new InnertubeError('Engagement panels not found. Video likely has no transcript.');
+
+    const transcript_panel = next_response.engagement_panels.get({
+      panel_identifier: 'engagement-panel-searchable-transcript'
+    });
+
+    if (!transcript_panel)
+      throw new InnertubeError('Transcript panel not found. Video likely has no transcript.');
+
+    const transcript_continuation = transcript_panel.content?.as(ContinuationItem);
+
+    if (!transcript_continuation)
+      throw new InnertubeError('Transcript continuation not found.');
+
+    const response = await transcript_continuation.endpoint.call(this.actions);
+
+    return new TranscriptInfo(this.actions, response);
+  }
+
   /**
    * Adds video to the watch history.
    */

src/parser/classes/StructuredDescriptionContent.ts

@@ -5,18 +5,24 @@ import HorizontalCardList from './HorizontalCardList.js';
 import VideoDescriptionHeader from './VideoDescriptionHeader.js';
 import VideoDescriptionInfocardsSection from './VideoDescriptionInfocardsSection.js';
 import VideoDescriptionMusicSection from './VideoDescriptionMusicSection.js';
-import type VideoDescriptionTranscriptSection from './VideoDescriptionTranscriptSection.js';
+import VideoDescriptionTranscriptSection from './VideoDescriptionTranscriptSection.js';
+import VideoDescriptionCourseSection from './VideoDescriptionCourseSection.js';
 
 export default class StructuredDescriptionContent extends YTNode {
   static type = 'StructuredDescriptionContent';
 
   items: ObservedArray<
     VideoDescriptionHeader | ExpandableVideoDescriptionBody | VideoDescriptionMusicSection |
-    VideoDescriptionInfocardsSection | VideoDescriptionTranscriptSection | HorizontalCardList
+    VideoDescriptionInfocardsSection | VideoDescriptionTranscriptSection | VideoDescriptionTranscriptSection |
+    VideoDescriptionCourseSection | HorizontalCardList
   >;
 
   constructor(data: RawNode) {
     super();
-    this.items = Parser.parseArray(data.items, [ VideoDescriptionHeader, ExpandableVideoDescriptionBody, VideoDescriptionMusicSection, VideoDescriptionInfocardsSection, HorizontalCardList ]);
+    this.items = Parser.parseArray(data.items, [
+      VideoDescriptionHeader, ExpandableVideoDescriptionBody, VideoDescriptionMusicSection,
+      VideoDescriptionInfocardsSection, VideoDescriptionCourseSection, VideoDescriptionTranscriptSection,
+      VideoDescriptionTranscriptSection, HorizontalCardList
+    ]);
   }
 }

src/parser/classes/StructuredDescriptionPlaylistLockup.ts

@@ -0,0 +1,34 @@
+import { YTNode } from '../helpers.js';
+import type { RawNode } from '../index.js';
+import NavigationEndpoint from './NavigationEndpoint.js';
+import Text from './misc/Text.js';
+import Thumbnail from './misc/Thumbnail.js';
+
+export default class StructuredDescriptionPlaylistLockup extends YTNode {
+  static type = 'StructuredDescriptionPlaylistLockup';
+
+  thumbnail: Thumbnail[];
+  title: Text;
+  short_byline_text: Text;
+  video_count_short_text: Text;
+  endpoint: NavigationEndpoint;
+  thumbnail_width: number;
+  aspect_ratio: number;
+  max_lines_title: number;
+  max_lines_short_byline_text: number;
+  overlay_position: string;
+
+  constructor(data: RawNode) {
+    super();
+    this.thumbnail = Thumbnail.fromResponse(data.thumbnail);
+    this.title = new Text(data.title);
+    this.short_byline_text = new Text(data.shortBylineText);
+    this.video_count_short_text = new Text(data.videoCountShortText);
+    this.endpoint = new NavigationEndpoint(data.navigationEndpoint);
+    this.thumbnail_width = data.thumbnailWidth;
+    this.aspect_ratio = data.aspectRatio;
+    this.max_lines_title = data.maxLinesTitle;
+    this.max_lines_short_byline_text = data.maxLinesShortBylineText;
+    this.overlay_position = data.overlayPosition;
+  }
+}

src/parser/classes/TranscriptSectionHeader.ts

@@ -0,0 +1,18 @@
+import { YTNode } from '../helpers.js';
+import type { RawNode } from '../index.js';
+import Text from './misc/Text.js';
+
+export default class TranscriptSectionHeader extends YTNode {
+  static type = 'TranscriptSectionHeader';
+
+  start_ms: string;
+  end_ms: string;
+  snippet: Text;
+
+  constructor(data: RawNode) {
+    super();
+    this.start_ms = data.startMs;
+    this.end_ms = data.endMs;
+    this.snippet = new Text(data.snippet);
+  }
+}

src/parser/classes/TranscriptSegmentList.ts

@@ -1,21 +1,22 @@
-import type { ObservedArray} from '../helpers.js';
+import type { ObservedArray } from '../helpers.js';
 import { YTNode } from '../helpers.js';
 import type { RawNode } from '../index.js';
 import Parser from '../index.js';
 import { Text } from '../misc.js';
+import TranscriptSectionHeader from './TranscriptSectionHeader.js';
 import TranscriptSegment from './TranscriptSegment.js';
 
 export default class TranscriptSegmentList extends YTNode {
   static type = 'TranscriptSegmentList';
 
-  initial_segments: ObservedArray<TranscriptSegment>;
+  initial_segments: ObservedArray<TranscriptSegment | TranscriptSectionHeader>;
   no_result_label: Text;
   retry_label: Text;
   touch_captions_enabled: boolean;
 
   constructor(data: RawNode) {
     super();
-    this.initial_segments = Parser.parseArray(data.initialSegments, TranscriptSegment);
+    this.initial_segments = Parser.parseArray(data.initialSegments, [ TranscriptSegment, TranscriptSectionHeader ]);
     this.no_result_label = new Text(data.noResultLabel);
     this.retry_label = new Text(data.retryLabel);
     this.touch_captions_enabled = data.touchCaptionsEnabled;

src/parser/classes/VideoDescriptionCourseSection.ts

@@ -0,0 +1,19 @@
+import type { ObservedArray} from '../helpers.js';
+import { YTNode } from '../helpers.js';
+import type { RawNode } from '../index.js';
+import Parser from '../index.js';
+import StructuredDescriptionPlaylistLockup from './StructuredDescriptionPlaylistLockup.js';
+import Text from './misc/Text.js';
+
+export default class VideoDescriptionCourseSection extends YTNode {
+  static type = 'VideoDescriptionCourseSection';
+
+  section_title: Text;
+  media_lockups: ObservedArray<StructuredDescriptionPlaylistLockup>;
+
+  constructor(data: RawNode) {
+    super();
+    this.section_title = new Text(data.sectionTitle);
+    this.media_lockups = Parser.parseArray(data.mediaLockups, [ StructuredDescriptionPlaylistLockup ]);
+  }
+}

src/parser/classes/misc/Format.ts

@@ -3,6 +3,8 @@ import { InnertubeError } from '../../../utils/Utils.js';
 import type { RawNode } from '../../index.js';
 
 export default class Format {
+  #this_response_nsig_cache?: Map<string, string>;
+
   itag: number;
   mime_type: string;
   is_type_otf: boolean;
@@ -52,7 +54,11 @@ export default class Format {
     matrix_coefficients?: string;
   };
 
-  constructor(data: RawNode) {
+  constructor(data: RawNode, this_response_nsig_cache?: Map<string, string>) {
+    if (this_response_nsig_cache) {
+      this.#this_response_nsig_cache = this_response_nsig_cache;
+    }
+
     this.itag = data.itag;
     this.mime_type = data.mimeType;
     this.is_type_otf = data.type === 'FORMAT_STREAM_TYPE_OTF';
@@ -122,6 +128,6 @@ export default class Format {
    */
   decipher(player: Player | undefined): string {
     if (!player) throw new InnertubeError('Cannot decipher format, this session appears to have no valid player.');
-    return player.decipher(this.url, this.signature_cipher, this.cipher);
+    return player.decipher(this.url, this.signature_cipher, this.cipher, this.#this_response_nsig_cache);
   }
 }

src/parser/generator.ts

@@ -134,33 +134,35 @@ export function isRendererList(value: unknown) {
  * @returns If it is a misc type, return the InferenceType. Otherwise, return false.
  */
 export function isMiscType(key: string, value: unknown): MiscInferenceType | false {
-  // NavigationEndpoint
-  if ((key.endsWith('Endpoint') || key.endsWith('Command') || key === 'endpoint') && typeof value === 'object' && value !== null) {
-    return {
-      type: 'misc',
-      endpoint: new NavigationEndpoint(value),
-      optional: false,
-      misc_type: 'NavigationEndpoint'
-    };
-  }
-  // Text
-  if (typeof value === 'object' && value !== null && (Reflect.has(value, 'simpleText') || Reflect.has(value, 'runs'))) {
-    const textNode = new Text(value);
-    return {
-      type: 'misc',
-      misc_type: 'Text',
-      optional: false,
-      endpoint: textNode.endpoint,
-      text: textNode.toString()
-    };
-  }
-  // Thumbnail
-  if (typeof value === 'object' && value !== null && Reflect.has(value, 'thumbnails') && Array.isArray(Reflect.get(value, 'thumbnails'))) {
-    return {
-      type: 'misc',
-      misc_type: 'Thumbnail',
-      optional: false
-    };
+  if (typeof value === 'object' && value !== null) {
+    // NavigationEndpoint
+    if (key.endsWith('Endpoint') || key.endsWith('Command') || key === 'endpoint') {
+      return {
+        type: 'misc',
+        endpoint: new NavigationEndpoint(value),
+        optional: false,
+        misc_type: 'NavigationEndpoint'
+      };
+    }
+    // Text
+    if (Reflect.has(value, 'simpleText') || Reflect.has(value, 'runs')) {
+      const textNode = new Text(value);
+      return {
+        type: 'misc',
+        misc_type: 'Text',
+        optional: false,
+        endpoint: textNode.endpoint,
+        text: textNode.toString()
+      };
+    }
+    // Thumbnail
+    if (Reflect.has(value, 'thumbnails') && Array.isArray(Reflect.get(value, 'thumbnails'))) {
+      return {
+        type: 'misc',
+        misc_type: 'Thumbnail',
+        optional: false
+      };
+    }
   }
   return false;
 }

src/parser/nodes.ts

@@ -328,6 +328,7 @@ export { default as SlimOwner } from './classes/SlimOwner.js';
 export { default as SlimVideoMetadata } from './classes/SlimVideoMetadata.js';
 export { default as SortFilterSubMenu } from './classes/SortFilterSubMenu.js';
 export { default as StructuredDescriptionContent } from './classes/StructuredDescriptionContent.js';
+export { default as StructuredDescriptionPlaylistLockup } from './classes/StructuredDescriptionPlaylistLockup.js';
 export { default as SubFeedOption } from './classes/SubFeedOption.js';
 export { default as SubFeedSelector } from './classes/SubFeedSelector.js';
 export { default as SubscribeButton } from './classes/SubscribeButton.js';
@@ -359,6 +360,7 @@ export { default as Transcript } from './classes/Transcript.js';
 export { default as TranscriptFooter } from './classes/TranscriptFooter.js';
 export { default as TranscriptSearchBox } from './classes/TranscriptSearchBox.js';
 export { default as TranscriptSearchPanel } from './classes/TranscriptSearchPanel.js';
+export { default as TranscriptSectionHeader } from './classes/TranscriptSectionHeader.js';
 export { default as TranscriptSegment } from './classes/TranscriptSegment.js';
 export { default as TranscriptSegmentList } from './classes/TranscriptSegmentList.js';
 export { default as TwoColumnBrowseResults } from './classes/TwoColumnBrowseResults.js';
@@ -371,6 +373,7 @@ export { default as VerticalList } from './classes/VerticalList.js';
 export { default as VerticalWatchCardList } from './classes/VerticalWatchCardList.js';
 export { default as Video } from './classes/Video.js';
 export { default as VideoCard } from './classes/VideoCard.js';
+export { default as VideoDescriptionCourseSection } from './classes/VideoDescriptionCourseSection.js';
 export { default as VideoDescriptionHeader } from './classes/VideoDescriptionHeader.js';
 export { default as VideoDescriptionInfocardsSection } from './classes/VideoDescriptionInfocardsSection.js';
 export { default as VideoDescriptionMusicSection } from './classes/VideoDescriptionMusicSection.js';

src/parser/parser.ts

@@ -367,15 +367,21 @@ export function parseResponse<T extends IParsedResponse = IParsedResponse>(data:
     parsed_data.playability_status = playability_status;
   }
 
-  const streaming_data = data.streamingData ? {
-    expires: new Date(Date.now() + parseInt(data.streamingData.expiresInSeconds) * 1000),
-    formats: parseFormats(data.streamingData.formats),
-    adaptive_formats: parseFormats(data.streamingData.adaptiveFormats),
-    dash_manifest_url: data.streamingData.dashManifestUrl || null,
-    hls_manifest_url: data.streamingData.hlsManifestUrl || null
-  } : undefined;
+  if (data.streamingData) {
+    // Currently each response with streaming data only has two n param values
+    // One for the adaptive formats and another for the combined formats
+    // As they are the same for a response, we only need to decipher them once
+    // For all futher deciphering calls on formats from that response, we can use the cached output, given the same input n param
+    const this_response_nsig_cache = new Map<string, string>();
+
+    const streaming_data = {
+      expires: new Date(Date.now() + parseInt(data.streamingData.expiresInSeconds) * 1000),
+      formats: parseFormats(data.streamingData.formats, this_response_nsig_cache),
+      adaptive_formats: parseFormats(data.streamingData.adaptiveFormats, this_response_nsig_cache),
+      dash_manifest_url: data.streamingData.dashManifestUrl || null,
+      hls_manifest_url: data.streamingData.hlsManifestUrl || null
+    };
 
-  if (streaming_data) {
     parsed_data.streaming_data = streaming_data;
   }
 
@@ -598,8 +604,8 @@ export function parseActions(data: RawData) {
   return new SuperParsedResult(parseItem(data));
 }
 
-export function parseFormats(formats: RawNode[]): Format[] {
-  return formats?.map((format) => new Format(format)) || [];
+export function parseFormats(formats: RawNode[], this_response_nsig_cache: Map<string, string>): Format[] {
+  return formats?.map((format) => new Format(format, this_response_nsig_cache)) || [];
 }
 
 export function applyMutations(memo: Memo, mutations: RawNode[]) {

src/parser/youtube/Playlist.ts

@@ -9,6 +9,7 @@ import PlaylistSidebarPrimaryInfo from '../classes/PlaylistSidebarPrimaryInfo.js
 import PlaylistSidebarSecondaryInfo from '../classes/PlaylistSidebarSecondaryInfo.js';
 import PlaylistVideoThumbnail from '../classes/PlaylistVideoThumbnail.js';
 import VideoOwner from '../classes/VideoOwner.js';
+import Alert from '../classes/Alert.js';
 
 import { InnertubeError } from '../../utils/Utils.js';
 import type { ObservedArray } from '../helpers.js';
@@ -17,7 +18,7 @@ import type Actions from '../../core/Actions.js';
 import type { ApiResponse } from '../../core/Actions.js';
 import type { IBrowseResponse } from '../types/ParsedResponse.js';
 
-class Playlist extends Feed<IBrowseResponse> {
+export default class Playlist extends Feed<IBrowseResponse> {
   info;
   menu;
   endpoint?: NavigationEndpoint;
@@ -29,9 +30,13 @@ class Playlist extends Feed<IBrowseResponse> {
     const header = this.memo.getType(PlaylistHeader).first();
     const primary_info = this.memo.getType(PlaylistSidebarPrimaryInfo).first();
     const secondary_info = this.memo.getType(PlaylistSidebarSecondaryInfo).first();
+    const alert = this.page.alerts?.firstOfType(Alert);
 
-    if (!primary_info && !secondary_info)
-      throw new InnertubeError('This playlist does not exist');
+    if (alert && alert.alert_type === 'ERROR')
+      throw new InnertubeError(alert.text.toString(), alert);
+
+    if (!primary_info && !secondary_info && Object.keys(this.page).length === 0)
+      throw new InnertubeError('Got empty continuation response. This is likely the end of the playlist.');
 
     this.info = {
       ...this.page.metadata?.item().as(PlaylistMetadata),
@@ -69,6 +74,4 @@ class Playlist extends Feed<IBrowseResponse> {
       throw new InnertubeError('Could not get continuation data');
     return new Playlist(this.actions, page, true);
   }
-}
-
-export default Playlist;
+}

src/parser/youtube/TranscriptInfo.ts

@@ -0,0 +1,55 @@
+import type Actions from '../../core/Actions.js';
+import { type ApiResponse } from '../../core/Actions.js';
+import type { IGetTranscriptResponse } from '../index.js';
+import Parser from '../index.js';
+import Transcript from '../classes/Transcript.js';
+
+export default class TranscriptInfo {
+  #page: IGetTranscriptResponse;
+  #actions: Actions;
+  transcript: Transcript;
+
+  constructor(actions: Actions, response: ApiResponse) {
+    this.#page = Parser.parseResponse(response.data);
+    this.#actions = actions;
+    this.transcript = this.#page.actions_memo.getType(Transcript).first();
+  }
+
+  /**
+   * Selects a language from the language menu and returns the updated transcript.
+   * @param language - Language to select.
+   */
+  async selectLanguage(language: string): Promise<TranscriptInfo> {
+    const target_menu_item = this.transcript.content?.footer?.language_menu?.sub_menu_items?.find((item) => item.title.toString() === language);
+
+    if (!target_menu_item)
+      throw new Error(`Language not found: ${language}`);
+
+    if (target_menu_item.selected)
+      return this;
+
+    const response = await this.#actions.execute('/get_transcript', {
+      params: target_menu_item.continuation
+    });
+
+    return new TranscriptInfo(this.#actions, response);
+  }
+
+  /**
+   * Returns available languages.
+   */
+  get languages(): string[] {
+    return this.transcript.content?.footer?.language_menu?.sub_menu_items?.map((item) => item.title.toString()) || [];
+  }
+
+  /**
+   * Returns the currently selected language.
+   */
+  get selectedLanguage(): string {
+    return this.transcript.content?.footer?.language_menu?.sub_menu_items?.find((item) => item.selected)?.title.toString() || '';
+  }
+
+  get page() {
+    return this.#page;
+  }
+}