Juddering (also known as stuttering) on a TV occurs when the movie's frame rate doesn't perfectly match the TV's refresh rate. Here are the main causes:

1. Different frame rates (e.g. 24 fps film on 60 Hz TV)

Movies are shot at 24 fps, but TVs often operate at 50 or 60 Hz.
Problem: 24 images cannot be divided evenly into 60 Hz or 50 Hz.

a) Solution: Pulldown method (in NTSC countries (USA, Canada, Japan):

A 24 fps film must be converted to 60 Hz using the 3:2 pulldown method:
- 1st frame > 3 TV frames
- 2nd frame > 2 TV frames
- 3rd frame > 3 TV frames etc.
This causes some frames to be shown for longer, resulting in uneven motion flow (judder).

b) Solution in PAL countries (Europe, Australia):

- Movies are often simply sped up from 24 fps to 25 fps (4% faster).
- This results in a slightly higher pitch (voices sound a little higher), but no judder.

c) Solution: TV with 24p support

When "Film Mode" is activated, the display shows the native 24 Hz frame rate. When switching between content with different frame rates, the image briefly goes black.

2. Mismatch between TV Hz and video FPS (e.g. 25 fps video on 60 Hz TV)

European TV channels and streaming services often broadcast at 25 or 50 fps. However, many TVs operate at 60 Hz, which isn't evenly divisible.

Problem: The TV has to repeat or interpolate frames, which can cause stuttering.

Solution:

- If the TV supports 50 Hz, select this setting.
- Some streaming services offer both versions (25 and 30 fps).

3. Motion smoothing (motion interpolation / soap opera effect)

Modern TVs use "motion smoothing" or "motion interpolation" to make the picture smoother. The problem is that the TV calculates artificial intermediate frames, creating 50 or 60 fps. This makes the film look unnaturally smooth (like a soap opera). Some TVs produce artifacts or blurring.

Solution:

Turn it off or set it to the lowest level for authentic cinematic playback. The feature is called something different depending on the manufacturer: Samsung "Auto Motion Plus," LG "TruMotion," Sony "MotionFlow," Philips "Perfect Natural Motion."

4. Streaming problems (network & compression)

Stuttering may occur on Netflix, Disney+ or Prime Video because:
- Adaptive streaming switches between frame rates (e.g. 24 fps 30 fps 24 fps).
- Poor internet connection causes frame drops.
- The TV has to "mix" different frame rates, which can appear jerky.

Solution:

- Stream directly to 24p compatible devices (e.g. Apple TV, Nvidia Shield).
- If possible, set a fixed frame rate in the streaming player.

What frame rates are used?

Frame rates (fps) vary by medium and region. Here are the most common standards for movies, TV, streaming, and Blu-ray:

1. Cinema & feature films

24 fps (frames per second) is the standard for cinematic films because it creates the "film look." 48 fps or higher is rarely used, for example, for high-frame-rate films like The Hobbit or Avatar.

2. Television & TV broadcasts

PAL regions (Europe, Asia, Australia): 25 fps (formerly analog, now 50 fps for smooth motion)

NTSC regions (USA, Canada, Japan): 29.97 fps (historically due to analog television standards)

Sports & Reality TV : 50 fps or 60 fps for smooth motion

Public television in Germany (Das Erste, ZDF, etc.) broadcasts in 720p 50Hz via satellite and cable or 1080p 50Hz via DVB-T2 HD.

German private TV channels use 576i 25Hz (free-to-air) and 1080i 25Hz (in paid HD versions). Sky 's Ultra HD offerings are broadcast in 2160p 50Hz (UHD option available for an additional charge).

3. Streaming services (Netflix, Disney+, YouTube, etc.)

• 24 fps for movies and series with a cinematic feel
• 25 or 30 fps for classic TV productions
• 50 or 60 fps for sports, gaming streams, and high-frame-rate content
• YouTube supports up to 60 fps for normal videos, some creators even use 120 fps

4. Blu-ray & UHD Blu-ray

Standard Blu-ray (1080p):

• 24 fps for feature films
• 50/60 fps for TV productions and documentaries

4K Ultra HD Blu-ray:

• 24 fps for feature films
• 60 fps possible, but rare (e.g. for nature documentaries or special productions)

It's quite astonishing that even modern productions for streaming remain at 24 fps. However, it corresponds to viewing habits and has a cinematic feel; it's compatible with existing production cameras, cinemas, and Blu-ray, and it saves storage and data transfer. High frame rates like 50 or 60 fps are more relevant for sports, gaming, and VR.