Download YouTube videos. Video formats are listed at the top of the watch page. Video links are tagged so that they can be downloaded easily.
This is due to how YouTube works. You have to download the video and audio streams and mux them yourself.
The only two videos with audio are 720p/MP4 and 360p/MP4. I presume they are for older devices.
下载的视频没有声音
下载的视频没有声音？ There is no sound in the downloaded video?