While this was working fine, it was actually not waiting for a proper
success signaling. This was clearly a race condition, as was
jeopardizing our error/timeout detection

And update to recent API changes

This fixes a contraint violation exception when trying to handle
multiple tracks, with the language as their only differences.

So that we can save all resources for playback

If handleMediaMeta is blocking, the timeout will try to acquire the sync
mutex, but won't manage to do so.
However, this only allows the parser to continue, but my guess would be
that there will still be a thread blocked somewhere

This has better performances than fetching all tracks and check for the
size of the vector