Video Frame Rates in Practice: 24, 25, 30, 60 and the Odd 29.97 Family

What frame rate measures

A video is a sequence of still frames shown quickly enough that the eye reads them as motion. The frame rate, in frames per second, says how many. Higher rates make motion smoother and capture fast action more clearly; lower rates give the slight motion blur and cadence people associate with cinema. Each frame is also a unit of storage and processing, so doubling the rate roughly doubles the work for an encoder or decoder, though not the file size, because similar consecutive frames compress well.

Frame rate is separate from the refresh rate of a display, which is how often the screen redraws, and from shutter speed, which is how long each frame was exposed. A 24 fps film shown on a 60 Hz screen and a 60 fps game shown on the same screen are both redrawn 60 times a second; only one of them has new pictures each time.

Where the common frame rates come from

24 fps

Standardized for sound film in the late 1920s as a compromise between smooth motion, intelligible optical sound and the cost of film stock. Still the cinema norm

25 fps

Television in regions with 50 Hz mains power, such as most of Europe, Africa, much of Asia and Australia, under the PAL and SECAM systems

50 fps

The same regions' full field rate, used today for sport, news and smooth progressive video

30 fps

Nominally the television rate in 60 Hz regions, such as North America and Japan, though broadcast actually uses 29.97

60 fps

Smooth motion for sport, games, screen recordings and phone video; in broadcast contexts often really 59.94

23.976 fps

24 fps slowed by a factor of 1000/1001, used when film-rate material is prepared for 60 Hz-region television and still common in camera settings

29.97 fps

30000/1001. The color television rate of 60 Hz regions

59.94 fps

60000/1001, the matching high-rate version

Mains frequency mattered because early television tied its field rate to the power supply to avoid visible flicker and hum bars. Interlaced television then delivered each frame as two fields, so 25 frames meant 50 fields per second and 30 frames meant 60. How fields work, and what they mean for footage today, is covered in interlaced vs progressive video.

Why 29.97 exists

When color was added to the North American television standard in the 1950s, engineers needed the new color signal to coexist with existing black-and-white sets and with the sound carrier without visible interference. The solution included lowering the frame rate very slightly, by a factor of 1000/1001, from 30 to about 29.97. Film transferred for those systems followed, giving 23.976, and higher rates gained the same factor, giving 59.94.

The difference sounds negligible, but it adds up. A video at 29.97 fps runs one frame behind a true 30 fps clock every 1,001 frames, which is about 3.6 seconds per hour. That is why broadcasters use drop-frame timecode for 29.97 material: it skips certain timecode numbers, two at the start of every minute except every tenth minute, so the timecode stays in step with the wall clock. No actual frames are dropped; only the labels skip.

Modern cameras and phones still offer both 29.97 and true 30, and 23.976 and true 24. Many devices label the fractional rates as 30 and 24 in their menus, so check a media inspector if the exact value matters.

Converting between frame rates

Changing a video's frame rate means inventing a different set of moments in time from the ones the camera captured. Every method has a cost.

• Dropping or repeating frames. Going from 60 to 30 by dropping every other frame is clean. Going from 24 to 30 means repeating some frames, which produces a slight irregular stutter in pans and steady motion.
• Frame blending. Each new frame is a mix of the two nearest originals. Motion looks smoother but moving objects show ghosted double edges.
• Motion-compensated interpolation. Software estimates movement and generates genuinely new in-between frames. It can look very smooth, but it fails on fast motion, crossing objects and fine detail, producing warping and halos.
• Speed change. Instead of inventing frames, the video is played faster or slower so every original frame is kept. Film shown on 25 fps television has traditionally been sped up by one twenty-fourth this way, which shortens the runtime and raises audio pitch slightly unless the audio is corrected.
• Pulldown. Film at 23.976 fps can be spread across 29.97 fps interlaced video by repeating fields in a 2:3 pattern. Inverse telecine reverses it and recovers the original frames, provided the pattern is intact.

Most of these require re-encoding, which costs quality and time. Our guide to converting video formats explains when re-encoding can be avoided altogether. Rates that change from moment to moment within one file are a separate subject, covered in variable frame rate explained.

Frame rate and subtitle timing

Subtitle formats fall into two camps, and the difference matters whenever frame rates change.

• Time-based formats such as SRT and WebVTT give start and end times in hours, minutes, seconds and milliseconds. They do not know or care about the frame rate. As long as the video's duration and timeline are unchanged, they stay in sync at any frame rate.
• Frame-based formats count frames instead. Some older subtitle files store frame numbers, and broadcast timecodes and formats such as EBU STL express times as hours, minutes, seconds and frames. Their meaning depends on the frame rate they assume, and applying them at a different rate makes them drift steadily.

Time-based subtitles do still break in one case: when a conversion changes speed. If a film is sped up from 24 to 25 fps, everything happens sooner, and every subtitle time needs to be scaled to match. Professional subtitlers also often align cue times to frame boundaries and express minimum gaps between cues in frames, which is one reason the target frame rate is part of a subtitle brief. Aligning cues with speech is covered in subtitle timestamp alignment.

Choosing a frame rate

1. If footage already exists, keep its frame rate through editing and export. Conversion is a last resort.
2. If you are shooting, use the rate your main audience's platforms and region expect: 25 or 50 in 50 Hz regions, 30 or 60 in 60 Hz regions, 24 for a cinematic look.
3. Avoid shooting under artificial light at a rate that does not match the local mains frequency, which can cause flicker in some lighting.
4. Use 60 fps for fast motion, screen recordings with scrolling or cursor movement, and anything that may be slowed down later.
5. For a talking-head video, any standard rate works. The extra smoothness of 60 fps rarely matters for speech-led content.
6. When mixing sources, pick one project rate and convert the minority footage, not the majority.

Frame rate mistakes and trade-offs

• Mixing 29.97 and 30 fps material and assuming they are the same, then finding a few seconds of drift in long timelines.
• Converting a whole project to a new rate for a minor platform preference, accepting stutter or blur everywhere for no real gain.
• Using frame-based subtitles or timecode lists with the wrong assumed rate.
• Treating 60 fps as automatically better. It doubles decoding work, can look unnaturally smooth for drama, and does nothing for content without motion.
• Speeding up 24 fps material to 25 without correcting the audio pitch when voices matter.

mydubly and frame rate

Frame rate does not affect transcription or translation in mydubly, because speech recognition works only on the audio, which is decoded in the browser and downmixed to 16 kHz mono. The video picture never leaves your device. Subtitles come as SRT and VTT, both time-based, with timings that refer to the original audio, so they fit the video at whatever frame rate it was recorded.

For dubbed videos, the original picture is copied packet by packet without re-encoding, so the frame rate, including any fractional or variable rate, is exactly what it was in your source. No conversion takes place. If you later convert the video's frame rate with a speed change, the subtitles and dubbed track will need the same scaling. The subtitle generator and the SRT generator page describe the subtitle output in more detail.

Next step: check what you really recorded

Open a few of your recent videos in a media inspector and note the exact frame rate, including whether it is 29.97 or 30 and whether it is constant. If your sources disagree, choose one project rate before editing; once a final export exists, you can create subtitles or a translated version with the mydubly video translator without touching its frame rate.