ELM applies three separate speed multipliers to media playback: Master Speed, Stage Speed and Media Speed. If any of them is not set to exactly 1, a video clip plays slightly faster or slower than real time and gradually drifts out of sync with any external source, such as a hardware video player, that you are trying to match.
Symptom
- A video loaded on a stage and played at "1.0x" does not run in real time.
- The live output speed does not match what the Media Monitor shows for the same clip.
- Timecode drifts further and further from a reliable reference player the longer the clip runs.
- The video finishes earlier or later than the length of the file you imported.
- Transcoding or re-encoding the media file makes no difference.
Cause
The effective playback rate is the combination of Master Speed, Stage Speed and Media Speed. All three default to 1, but any of them can end up off after manual adjustment or after importing a clip that carries a different setting. Dragging a slider back by eye often lands on a value that is close to 1 but not exactly 1, and even a tiny offset accumulates into visible timecode drift over the length of a clip.
Fix
- Check Master Speed.
- Check Stage Speed for the stage that plays the clip.
- Check Media Speed for the media slot holding the clip.
- To reset a value, double-click the blue bar next to the control. This snaps it back to exactly 1. Do not drag the slider back by hand, because you can end up near 1 without being exactly on it.
- Play the clip again alongside your reference source and confirm the timecode no longer drifts.
Notes
- A speed value of 1 is not an absolute playback rate. It is a multiplier applied to the clip you uploaded, so the actual output rate depends on the video file itself. If the file was encoded at the wrong frame rate, fix the source file; the speed controls will not correct it.
- Playback speed also affects load: running media at 2x doubles the frames per second ELM has to render and roughly halves the number of videos you can play at the same time. If you see stutter after speed changes, see ELM CPU Usage is high.
Related resources
- Video Content Guidelines for recommended codecs and encoding settings.
- ELM user manual for the full reference on stages, media slots and sequences.