Does frame rate affect SRT files?

Not directly, because SRT expresses time in seconds and milliseconds. It matters when converting to or from a frame-based format.

What is 29.97 fps really?

It is 30 frames per second slowed by a factor of 1000/1001, a legacy of NTSC colour encoding. It is the reason drop-frame timecode exists.

Can I mix frame rates in one delivery?

Only if the specification allows it. Most broadcast specifications require a single rate throughout.

How do I find the frame rate of a file?

Any media inspector will report it, and most video tools show it in file properties. Check it rather than assuming, because a file delivered as 30 fps is frequently 29.97, and that difference is exactly what causes caption drift across a long programme.

Definition

What Is Frame Rate?

VideoText editorial team. Updated September 13, 2026.

Direct definition

Frame rate is how many video frames are displayed per second — 24, 23.976, 25, 29.97, 30, 50, 59.94, and others. Caption timing that assumes the wrong rate will drift.

The sections below explain how frame rate is used in transcription and subtitle work, what people often mix up, and which VideoText workflow applies when the next step is a file or review pass.

Key takeaways

Confirm fps before converting between frame-based and millisecond cues.
23.976 is not 24. 29.97 is not 30.
Players that ignore the source fps will still play the video; your sidecar file may not stay aligned.

Example

A one-hour program at 23.976 vs 24 “loses” a few seconds of alignment if someone treats the counts as identical. That error is visible at the end of a long SRT.

Common rates and where they come from

Film runs at 24 fps, PAL-region broadcast at 25, and NTSC-region at 29.97 — a fractional rate inherited from colour television. Web video is commonly 30 or 60, and high-motion material may be higher still.

The rate is a property of the material, not a setting you pick afterwards. Changing it after the fact means either duplicating or discarding frames, both of which alter motion.

Why captions care about it

Any format that expresses time in frames rather than seconds needs the rate to be interpreted. A timecode of 01:00:00:12 is a different instant at 24 fps than at 30.

Sync errors that grow steadily across a programme, rather than appearing all at once, are almost always a frame rate assumption mismatch somewhere in the chain.

Frequently asked questions

Does frame rate affect SRT files?: Not directly, because SRT expresses time in seconds and milliseconds. It matters when converting to or from a frame-based format.
What is 29.97 fps really?: It is 30 frames per second slowed by a factor of 1000/1001, a legacy of NTSC colour encoding. It is the reason drop-frame timecode exists.
Can I mix frame rates in one delivery?: Only if the specification allows it. Most broadcast specifications require a single rate throughout.
How do I find the frame rate of a file?: Any media inspector will report it, and most video tools show it in file properties. Check it rather than assuming, because a file delivered as 30 fps is frequently 29.97, and that difference is exactly what causes caption drift across a long programme.

Related terms

Sources

SMPTE: SMPTE Standards