I was writing an mp3player script while I hit few .mp3s that mIRC 6.35 was unable to play using /splay. Error message being: "/splay unable to play: <filename>"
This was on Vista, where I use newest ffdshow codecs rev. 3029 (20090710). I tried playing the files on Winamp, VLC, GomPlayer and they played it fine. I moved the errorous files to my another computer, which has XP and the same codec pack and mIRC versions and the files played fine with /splay and Winamp etc.
I visited couple friends that had XPs, Vistas and 7s installed. All XPs were able to play the files with /splay, while all Vistas, and 7s weren't.
So I started to investigate further by editing headers of the files in Winamp. When I came to remove id3v2 tags from the files, they suddenly started playing with /splay on Vista.
Even if the id3v2 was somehow errorous, that should't prevent it from playing when every other player is able do it. Songs I encountered the problem with were from few different albums. While most of the files on those albums ran into the same error, there were couple songs that didn't.
It's a shame I probably can't send the files I ran in to error with, since it's copyrighted work we are talking about.
If I discover something more, I'll be posting.