Why in the videos on YouTube sound quality differs from mp3

[readytowok]

Why in the video sound quality differs from mp3
That's the shit
I watch videos on YouTube and do not understand that such a sound, are in view of the commercial clips

I'm just not familiar with video production

 

[ido1957]

Low resolution MP3 removes a lot of information from an audio track.
Commercial clips are higher resolution so they sound better.
Plus I don't think YT pummels the audio as bad a say Soundcloud does.

 

[Pinky]

Good videos use full CD quality WAVs in the upload, then when Youtube compresses for streaming their's some quality loss but not as noticeable than if you used MP3 in the original uploaded content.