How to detect whether HTML5 video has paused for buffering?

Question

I'm trying to test whether a video is choppy. I have noticed that the pause event is not triggered when the video pauses for buffering. What is the best way to detect whether the video has paused for buffering?

Answer 1

I did this by inspecting the player progress every x milliseconds, e.g. 50. If the player hasn't advanced as much as it was expected to, then we are buffering. This is quite reliable, since I've found that other events such as waiting or stalled are not fired in all cases of the video buffering.

Note that the interval must be larger than the expected inter-frame difference, but I'm sure that you won't want to be that precise anyway. An estimation of buffering time within ±300ms would still be fine, given that humans most likely cannot perceive differences in that region.

It is important to check whether the user hasn't actively paused the playback though.

var checkInterval  = 50.0 // check every 50 ms (do not use lower values) var lastPlayPos    = 0 var currentPlayPos = 0 var bufferingDetected = false var player = document.getElementById('videoPlayer')  setInterval(checkBuffering, checkInterval) function checkBuffering() {     currentPlayPos = player.currentTime      // checking offset should be at most the check interval     // but allow for some margin     var offset = (checkInterval - 20) / 1000      // if no buffering is currently detected,     // and the position does not seem to increase     // and the player isn't manually paused...     if (             !bufferingDetected              && currentPlayPos < (lastPlayPos + offset)             && !player.paused         ) {         console.log("buffering")         bufferingDetected = true     }      // if we were buffering but the player has advanced,     // then there is no buffering     if (         bufferingDetected          && currentPlayPos > (lastPlayPos + offset)         && !player.paused         ) {         console.log("not buffering anymore")         bufferingDetected = false     }     lastPlayPos = currentPlayPos } 

Answer 2

The event you're looking for is waiting.

From the spec:

A waiting DOM event can be fired as a result of an element that is potentially playing stopping playback due to its readyState attribute changing to a value lower than HAVE_FUTURE_DATA.

The paused state does not change because the video is still "potentially playing" (i.e. "trying" to play). So the waiting event fires. When enough data has been loaded, playing fires.

You can also check the state at any time by looking at two properties, networkState and readyState

if (video.networkState === video.NETWORK_LOADING) {     // The user agent is actively trying to download data. }  if (video.readyState < video.HAVE_FUTURE_DATA) {     // There is not enough data to keep playing from this point }