Transcode video with NodeJS

This time I will bring you how to use NodeJS to transcode videos, and what are the precautions for using NodeJS to transcode videos. The following is a practical case, let's take a look.

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.

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

Let me introduce to you how to implement video transcoding in NodeJS.

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 use the command line to transcode the video using the ffmpeg command. 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-fluent-ffmpeg moduleBasic usagemethod

node-fluent-ffmpeg is essentially executing 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 via npm (npm install fluent-ffmpeg), 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 examples

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 perform chain calls. Just after instantiation, a series of video attributes are set in the chain, and finally the end event is listened to, 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 ffmpeg can do, and perform any processing on the video. 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

Each function above sets various attributes of the video. Below is a brief introduction to some of the more important attributes in video transcoding, as well as their corresponding methods in node-fluent-ffmpeg.

1.fps: The frame rate of the video, indicating how many times the picture is refreshed in 1 second. 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. Bit rate: In the video field, generally speaking, the bit 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.                                                                                                                                                                                                                                                                                                          

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