It occurred to me that the AsyncIterator we get via allMetrics() might simply not produce any items. I added an extra diagnostic message just after the for-loop in the above code, and that message is also never displayed - so it seems like the iterator does wait indefinitely for metrics to be produced, as I was expecting. let playerItem: AVPlayerItem = ... let allMetrics = playerItem.allMetrics() Task.init { print("metrics task started") // appears in output do { for try await metricEvent in allMetrics { print("metric event: \(metricEvent.description)"). // does not appear } print("metrics task done") // also does not appear } catch { print("unexpected metric iterator error \(error)") } } Don't know what to try next to get access to this data.