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.
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The only three video streams with audio are 720/MP4, 360/MP4 and 360/WEBM.
The rest are either video or audio streams. That's just how YouTube works now.
If you want high-res video, you got to do the work yourself. Download the video and audio streams, then mux'ed them.
You can do this using youtube-dl, for example. It downloads directly from YouTube and muxes the streams for you.
The downloaded video has no sound
Why is the downloaded video soundless?