File size: 4,862 Bytes
f8b5d42 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 | class YoutubeTranscriptError extends Error {
constructor(message) {
super(`[YoutubeTranscript] ${message}`);
}
}
/**
* Handles fetching and parsing YouTube video transcripts
*/
class YoutubeTranscript {
/**
* Encodes a string as a protobuf field
* @param {number} fieldNumber - The protobuf field number
* @param {string} str - The string to encode
* @returns {Buffer} Encoded protobuf field
*/
static #encodeProtobufString(fieldNumber, str) {
const utf8Bytes = Buffer.from(str, "utf8");
const tag = (fieldNumber << 3) | 2; // wire type 2 for string
const lengthBytes = this.#encodeVarint(utf8Bytes.length);
return Buffer.concat([
Buffer.from([tag]),
Buffer.from(lengthBytes),
utf8Bytes,
]);
}
/**
* Encodes a number as a protobuf varint
* @param {number} value - The number to encode
* @returns {number[]} Encoded varint bytes
*/
static #encodeVarint(value) {
const bytes = [];
while (value >= 0x80) {
bytes.push((value & 0x7f) | 0x80);
value >>>= 7;
}
bytes.push(value);
return bytes;
}
/**
* Creates a base64 encoded protobuf message
* @param {Object} param - The parameters to encode
* @param {string} param.param1 - First parameter
* @param {string} param.param2 - Second parameter
* @returns {string} Base64 encoded protobuf
*/
static #getBase64Protobuf({ param1, param2 }) {
const field1 = this.#encodeProtobufString(1, param1);
const field2 = this.#encodeProtobufString(2, param2);
return Buffer.concat([field1, field2]).toString("base64");
}
/**
* Extracts transcript text from YouTube API response
* @param {Object} responseData - The YouTube API response
* @returns {string} Combined transcript text
*/
static #extractTranscriptFromResponse(responseData) {
const transcriptRenderer =
responseData.actions?.[0]?.updateEngagementPanelAction?.content
?.transcriptRenderer;
if (!transcriptRenderer) {
throw new Error("No transcript data found in response");
}
const segments =
transcriptRenderer.content?.transcriptSearchPanelRenderer?.body
?.transcriptSegmentListRenderer?.initialSegments;
if (!segments) {
throw new Error("Transcript segments not found in response");
}
return segments
.map((segment) => {
const runs = segment.transcriptSegmentRenderer?.snippet?.runs;
return runs ? runs.map((run) => run.text).join("") : "";
})
.filter((text) => text)
.join(" ")
.trim()
.replace(/\s+/g, " ");
}
/**
* Fetch transcript from YouTube video
* @param {string} videoId - Video URL or video identifier
* @param {Object} config - Configuration options
* @param {string} [config.lang='en'] - Language code (e.g., 'en', 'es', 'fr')
* @returns {Promise<string>} Video transcript text
*/
static async fetchTranscript(videoId, config = {}) {
const identifier = this.retrieveVideoId(videoId);
const lang = config?.lang ?? "en";
try {
const innerProto = this.#getBase64Protobuf({
param1: "asr",
param2: lang,
});
const params = this.#getBase64Protobuf({
param1: identifier,
param2: innerProto,
});
const response = await fetch(
"https://www.youtube.com/youtubei/v1/get_transcript",
{
method: "POST",
headers: {
"Content-Type": "application/json",
"User-Agent":
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36,gzip(gfe)",
},
body: JSON.stringify({
context: {
client: {
clientName: "WEB",
clientVersion: "2.20240826.01.00",
},
},
params,
}),
}
);
if (!response.ok) {
throw new Error(`HTTP error! status: ${response.status}`);
}
const responseData = await response.json();
return this.#extractTranscriptFromResponse(responseData);
} catch (e) {
throw new YoutubeTranscriptError(e.message || e);
}
}
/**
* Extract video ID from a YouTube URL or verify an existing ID
* @param {string} videoId - Video URL or ID
* @returns {string} YouTube video ID
*/
static retrieveVideoId(videoId) {
if (videoId.length === 11) return videoId;
const RE_YOUTUBE =
/(?:youtube\.com\/(?:[^\/]+\/.+\/|(?:v|e(?:mbed)?)\/|.*[?&]v=)|youtu\.be\/)([^"&?\/\s]{11})/i;
const matchId = videoId.match(RE_YOUTUBE);
if (matchId?.[1]) return matchId[1];
throw new YoutubeTranscriptError(
"Impossible to retrieve Youtube video ID."
);
}
}
module.exports = {
YoutubeTranscript,
YoutubeTranscriptError,
};
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