I hope that SMPlayer can playback all videos included in a playlist at a same speed.
The current version of SMPlayer can't do it.
I often playback a video at 1.5 times speed.
The reason why I use SMPlayer is that it can playback at 1.5 times speed.
But you can't playback all videos included in a playlist at 1.5 times speed if you select "1.5 times speed".
Only the first video in a playlist playbacks at 1.5 times speed if you select "1.5 times".