foreword
With the continuous increase of video content, how to quickly and accurately retrieve the desired video has become an important issue. The video text feature accelerated retrieval solution - inverted index, has become an effective means to solve this problem. This technology can speed up the feature matching and similarity ranking process of text and video clips!
Definition - what is an "inverted index"
An inverted index is a data structure that maps each word in a document to a list of documents that contain that word. This data structure can quickly find documents containing specific words, so it is widely used in search engines and text retrieval.
In the accelerated retrieval of video text features, we can use the text features of each video (such as title, description, etc.) as a document, and map each word to a list of videos containing that word. In this way, when the user enters a keyword to search, we only need to find the list of videos containing the keyword in the inverted index instead of traversing the text features of all videos, thus greatly improving the retrieval efficiency.
Front-end vue sample code - text retrieval video feature fragment
The following is a simple sample front-end js code to demonstrate how to use inverted index for video text feature retrieval:
```javascript
// define inverted index
var invertedIndex = {};
// Add video text feature to inverted index
function addVideoToInvertedIndex(video) { var words = video.text.split(' '); for (var i = 0; i < words.length; i++) { var word = words [i]; if (!invertedIndex[word]) { invertedIndex[word] = []; } invertedIndex[word].push(video); } }
// Search keywords
function search(keyword) { var videos = invertedIndex[keyword]; if (videos) { // Display search results for (var i = 0; i < videos.length; i++) { var videos = videos[ i]; console.log(video.title); } } else { console.log('No results found.'); } }
// 示例视频
var video1 = {
title: 'How to make a cake',
text: 'Learn how to make a delicious cake from scratch.'
};
var video2 = {
title: 'Introduction to JavaScript',
text: 'This video introduces the basics of JavaScript programming.'
};
// Add the sample video to the inverted index
addVideoToInvertedIndex(video1);
addVideoToInvertedIndex(video2);
// Search keyword
search('JavaScript'); // Output: Introduction to JavaScript
```
Through the inverted index, we can quickly find videos containing specific keywords, thereby improving retrieval efficiency. Of course, the inverted index also has some disadvantages, such as requiring a large amount of memory space and requiring regular updates. However, in the accelerated retrieval of video text features, inverted index is still a very effective solution.
Supplementary - word document matrix
Basic concept of inverted index
Document: The processing object of general search engines is Internet web pages, and the concept of documents is broader, representing storage objects in the form of text. Compared with web pages, it covers more forms, such as Word, PDF, Files in different formats such as html and XML can be called documents. Another example is an email, a text message, or a Weibo, which can also be called a document.
Document Collection (Document Collection): A collection composed of several documents is called a Document Collection. For example, a large number of Internet pages or a large number of e-mails are specific examples of document collections.
Document ID: Inside the search engine, each document in the document collection will be given a unique internal number, and this number will be used as the unique identifier of the document, which is convenient for internal processing. The internal number of each document is It is called "document number", and later DocID is sometimes used to conveniently represent the document number.
Word ID (Word ID): Similar to the document ID, the search engine internally uses a unique number to represent a word, and the word ID can be used as a unique representation of a word.
Inverted Index: Inverted Index is a specific storage form to realize the "word-document matrix". Through the inverted index, the list of documents containing this word can be quickly obtained according to the word. The inverted index mainly consists of two parts: "word dictionary" and "inverted file".
Word dictionary (Lexicon): The usual index unit of a search engine is a word. The word dictionary is a string collection composed of all words that have appeared in the document collection. Each index item in the word dictionary records some information about the word itself and points to the "inverted Arrangement list" pointer.
Posting List (PostingList): The posting list records the document list of all documents where a certain word appears and the position information of the word appearing in the document. Each record is called a posting item (Posting). According to the inverted list, you can know which documents contain a certain word.
Inverted File: The inverted list of all words is often stored sequentially in a file on the disk. This file is called an inverted file, and the inverted file is a physical file that stores the inverted index.
The relationship between these concepts can be clearly seen from the figure below.
references:
[1] https://en.wikipedia.org/wiki/Inverted_index
[2] https://www.elastic.co/guide/en/elasticsearch/guide/current/inverted-index.html