Separate startup from ongoing playback
Measure the interval between the play request and first decoded frame. Record stalls during playback separately. Compare these signals with media request failures and quality changes to understand whether startup, bandwidth, or the source needs attention.
Run a controlled failure
Use a known media asset and simulate a delay, missing segment, or unavailable source. Record the player state, source response, and recovery behavior. Keep these cases available for future runs so a player or delivery change can be compared with the same baseline.