Example analysis of NodeJS video transcoding

Video transcoding is a process of first decoding and then encoding, thereby converting the original video into the video we need. This conversion may include various formats (mp4/avi/flv, etc.), resolution, bit rate, frame rate, etc. In traditional video transcoding, a very commonly used tool is FFmpeg. FFmpeg is a set of open source computer programs that can be used to record, convert digital audio and video, and convert them into streams. In nodejs, there is also FFmpeg, called node-fluent-ffmpeg. node-fluent-ffmpeg is an ffmpeg available on node. ffmpeg must be installed before use. This article mainly introduces the sample code for video transcoding in NodeJS. I hope it can help everyone.

ffmpeg

FFmpeg is a set of open source computer programs that can be used to record, convert digital audio and video, and convert them into streams. Use LGPL or GPL license. It provides a complete solution for recording, converting and streaming audio and video. It contains the very advanced audio/video codec library libavcodec. In order to ensure high portability and codec quality, many codes in libavcodec are developed from scratch.

The following is an introduction to NodeJS for video conversion. coding method.

1. Install FFmpeg (under MAC)

Under MAC, you can directly use the brew command to install: brew install ffmpeg.

After the installation is successful, we can proceed on the command line and use the ffmpeg command to transcode the video. For example, to transcode input.avi into output.ts and set the video bit rate to 640kbps, the commands that need to be executed are as follows:

ffmpeg -i input.avi -b:v 640k output.ts

2. node- The basic usage of the fluent-ffmpeg module

node-fluent-ffmpeg is essentially to execute FFmpeg commands in the terminal through nodejs. The installation and basic introduction of node-fluent-ffmpeg are the same as other npm modules. After installing it through npm (npm install fluent-ffmpeg), just use require to reference it in the js file. The basic usage is as follows:

var ffmpeg = require(‘fluent-ffmpeg'); 
var command = new ffmpeg(这里可以传入视频文件路径，或者流);

In this way, a command line is instantiated, and the video file to be transcoded needs to be passed in. The form of data stream is also supported.

3. Usage Example

The following is an example of using node-fluent-ffmpeg for video transcoding:

var ffmpeg = require('../index'); 
var command = ffmpeg('testvideo-5m.mpg') 
 // set video bitrate 
 .videoBitrate(1024) 
 // set aspect ratio 
 .aspect('16:9') 
 // set size in percent 
 .size('50%') 
 // set fps 
 .fps(24) 
 // set audio bitrate 
 .audioBitrate('128k') 
 // set audio codec 
 .audioCodec('libmp3lame') 
 // set number of audio channels 
 .audioChannels(2) 
 // set custom option 
 .addOption('-vtag', 'pX') 
 // set output format to force 
 .format('avi') 
 // setup event handlers 
 .on('end', function() { 
  console.log('file has been converted succesfully'); 
 }) 
 .on('error', function(err) { 
  console.log('an error happened: ' + err.message); 
 }) 
 // save to file 
 .save('outtest.avi');

node-fluent-ffmpeg can be called in a chain. Just after instantiation, a series of video attributes are set in the chain, and finally the end event is monitored, indicating that the video has been transcoded. After completion, the save() method can be called to store the video file in the corresponding directory.

4. What node-fluent-ffmpeg can do

node-fluent-ffmpeg can do anything that ffmpeg can do, and perform any processing on the video. deal with. In addition, with nodejs, node-fluent-ffmpeg can also do many other things, such as reading and dynamically returning the length of the video, transcoding the video into any format as required, etc. The specific methods can be viewed on github, which has an introduction to the methods. When using it, you can easily complete the video transcoding by simply picking up what you need.

5. Some elements of video transcoding

The above functions set various attributes of the video. Here is a brief introduction to video transcoding. Some of the more important attributes and their corresponding methods in node-fluent-ffmpeg.

1.fps: The frame rate of the video, indicating how many times the picture is refreshed in 1s. When playing games, we all know that if the fps is low, the game will be laggy. This is the role of fps. The higher the fps within a certain range, the higher the number of times the video is refreshed per second, and the smoother it appears to the human eye. The corresponding method of this attribute is fps(), just pass in the frame rate value you want to set.

2. Resolution: Used to set the size of the video. The corresponding method is size(), passing in width x height.

3. Code rate: In the video field, generally speaking, the code rate refers to the bit rate. It represents the number of data bits transmitted per unit time during data transmission, in kbps. This value affects the video quality. The larger the value, the higher the quality of the video, but at the same time, the size of the video file will be larger. Therefore, we need to set the code rate reasonably when transcoding to ensure that the quality is as high as possible while the file size does not exceed the limit.

4. Format: Needless to say, the format can be set through the format method.

Related recommendations:

Solution to the problem of Chinese UNICODE transcoding in json_encode in php

About character transcoding Detailed introduction

File transcoding gadget written in python

The above is the detailed content of Example analysis of NodeJS video transcoding. For more information, please follow other related articles on the PHP Chinese website!