There are several methods.

1. Recording: This is the simplest and crudest method. Whether it is a video on a computer or a video on a mobile phone, you can record background music through recording. But computers and mobile phones are not professional recording equipment after all. The quality of the recorded audio cannot be compared with the original audio, and there is still a lot of noise;

2. Modify the suffix: Find the video in the mobile file manager file, change the suffix to ".mp3". The same is true for how to operate a computer. This way you can directly convert video files into audio files. However, it should be noted that this method may cause the file to be damaged or unable to be played;