schrolock
commented
5 years ago that's simply because Youtube uses software, to alter the sped up sound, to closely resemble the original sound, while this program simply speeds it up, without, 'normalizing' the sound.
If you need to have unaltered sound, you could use this software to cut out silence and then use another video editor to speed it up with normalized sounds, or if you want to make it complicated, use a video editor, to make a individual sound file, speed up the video, and remember how much you sped it up, then "speed up without changing pitch" with Audacity, increasing the speed the same as the video and then finally edit it together again, giving you a finished video
Sample video - https://www.youtube.com/watch?v=vDXkpJw16os&t=172s
When changing speed on using the YouTube builtin tool to 1.25x their is very little change in the pitch of the audio, it sounds the same only faster.
When changing --sounded_speed to 1.25, their is a very noticeable change in the pitch of the audio on my system. The output video sounds deeper and slightly muffled compared to the original and the original speed up with youtubes speed tool.
When audio is speed up it normally has a higher pitch, for this reason I think the program is over correcting.
Is any one else having this issue with audio?