# How to measure the time-to-first-frame on Roku

The time-to-first-frame, also known as the start-up time, is the time between the moment where playback is requested and the moment where the first frame is rendered.

To measure it, measure the time between the `play` event and the `playing` event.

## Usage

On Roku, you measure the elapsed time with a [`roTimespan`](https://developer.roku.com/docs/references/brightscript/interfaces/iftimespan.md).

```brightscript
sub Init()
  ...
  m.timespan = CreateObject("roTimespan")
  m.THEOplayer.callFunc("addEventListener", "play", m.top, "onPlay")
  m.THEOplayer.callFunc("addEventListener", "playing", m.top, "onPlaying")
  ...
end sub

sub onPlay()
  m.timespan.Mark()
end sub

sub onPlaying()
  print "Time-to-first-frame: "; m.timespan.TotalMilliseconds()
end sub
```

If you use autoplay, start the measurement on the `sourcechange` event instead of the `play` event. Otherwise you miss the start-up time between setting the source and the player calling `play()`:

```brightscript
m.THEOplayer.callFunc("addEventListener", "sourcechange", m.top, "onSourceChange")

sub onSourceChange()
  m.timespan.Mark()
end sub
```