I check video current time. I assume playback is started when curent time begins to change.
You could listen for BUFFER_FULL event. There are very rare cases when the video starts playing and the player never gets to a BUFFER_FULL, though we have not met one in normal use.
The measurement values actually reflect close enough the start of the playback.
Using the PLAYING event will not help you so much, since it will be triggered when the video starts to load.
Thanks for the replies - I had tried the Buffer_Full but, was not confident of its reliablility. The time change is interesting and I will look at that.