YTVolume Normalizer от User 17470389

This extension uses DynamicsCompressor to adjust the volume of YouTube videos evenly.
YouTube has a loudness normalization feature. Normally, the maximum volume of a video is measured, and if it is louder than the standard, the volume is processed to lower it. Therefore, the volume fluctuations in the video (the difference between the smallest and loudest parts) are maintained. Specifically, if one part of the video is very loud and another part is quiet, YouTube will lower the overall volume to match the loudest part. Also, if the maximum volume of the video is lower than the standard, the volume will not be amplified.