IIRC (it's been many years) after many loops that animation started desyncing in the real Flash player too. It wasn't terribly noticeable after only a few loops, but the fact that it happened made me think that the audio loop was completely async from the animation.
Re:Firefox 84.0
by Snitch-Thursday on Tuesday December 15, 2020 @01:23PM
(#25433192)
I just tried the above animation on W10 + uBo + Firefox 83. I went through 3 loops and it seemed to stay in sync. Then I hopped over to check this comment and came back to that tab, and it was out of sync at that time. So I think Tab Switching might be a challenge for Ruffle.
Clearly Ruffle is not perfect, but leagues, furlongs ahead of having to watch old flash content on YouTube via Unregistered Hypercam 2.
https://archive.org/details/flash_badger
On Chrome the animation starts lagging behind after a few loops so audio and video desync badly. On Firefox it’s much worse, since Firefox is naturally slower than Chrome so even the first loop is desynced already.