Guides

25p in 50p: doubled frames – error or delivery format?

Edit 25p footage in a 50p sequence or export it as 50p, and every frame appears twice. That does not stutter in the strict sense – the motion stays even – but it is not real 50 frames per second. Whether that is a problem depends on what has to be delivered.

When it is fine

If the client or broadcaster requires 50p as the delivery format and the footage is 25p, doubling is common and usually intended. Whether footage at a lower frame rate is allowed is stated in the technical delivery specifications – check them if in doubt.

When it is an error

• Only one section is doubled while the rest has real 50 frames: then a clip has been slowed down to 50 % or has the wrong frame rate. Slowed-down clip
• 50p footage was treated as 25p – for example exported through a 25p sequence and brought back to 50p. Then real motion phases are missing.

Fixes in Premiere Pro

• 25 fps delivery allowed: Sequence → Sequence Settings → set Timebase to 25 and export like that.
• Real 50 frames per second required: Clip → Video Options → Time Interpolation → “Optical Flow”. Check the result frame by frame – fast motion can cause smearing.
• Check the clips’ frame rate: “Media Frame Rate” column in the Project panel.

In After Effects

Layer → Frame Blending → Pixel Motion, and turn on the composition’s “Frame Blending” switch – After Effects then calculates the in-between frames.

Other causes of stutter: Video stutters after export.