4K Video Playback and Aspect Ratio Comparison

Check original 4K playback and compare frame shapes

The player above streams a 3840 × 2160 MP4 at 60 fps, approximately 62 seconds long with audio, using the browser’s native video element. It combines a known source size with selectable viewing-window shapes and timing readouts. Use it to inspect playback consistency and understand cropping. A 4K source can be decoded and scaled onto a smaller screen, so successful playback does not establish that the physical panel is 4K.

How to use the tool

1. Choose 16:9 original and press Play in the native controls. Give the file time to buffer, then inspect moving edges, fine texture and dark areas before changing the viewing shape.
2. Read Source video resolution after metadata loads. Compare the presented-video FPS estimate with browser frame cadence while playback is active; they describe different parts of the pipeline.
3. Select 1.43:1, 1.85:1, 1.90:1, 2.20:1 or 2.39:1. Watch how the same scene fills each frame, especially subjects near the edges.
4. Pause or seek to a recognizable moment for a fair composition comparison. Changing frame shape preserves the video position and does not switch the source file or encoded quality.

Understand what gets cropped

The frame-shape controls change the player’s width-to-height relationship, while the video fills the frame using a cover crop. A wider frame than the 16:9 source removes some content above and below. A narrower frame removes some content at the sides. The video is scaled to fill the window rather than stretched into a new shape.

For example, 2.39:1 gives the landscape a wider viewing window, but it does not reveal extra scenery that was never present in the original file. A subject near the top may disappear from that crop. A 1.43:1 window can instead hide side content. Return to 16:9 to inspect the complete source composition.

These choices are demonstrations of framing, not alternate film masters. They do not add pixels, change the source aspect ratio or produce a different encode. Use the aspect ratio calculator if you want to simplify a width and height from another file.

Read the two timing indicators

Presented video FPS uses video-frame callbacks when the browser provides that API. The page estimates the callback frequency over a recent window during playback. This is useful for comparing sessions, but it is not a count of physical display refreshes or a certified source-frame-rate measurement.

Browser frame cadence uses animation callbacks independently of the video. A video could report around 30 FPS while the page’s cadence is around 60 or 120. That difference is expected: a display can refresh more frequently than new video frames arrive. Additional refreshes do not automatically create additional motion detail.

If video-frame callbacks are unavailable, the player says that the FPS reading is unavailable. Playback itself can still work. A paused readout should be compared with another paused state, rather than treated as poor playback performance.

Troubleshoot buffering, errors or uneven motion

If playback pauses to load data, check the connection and wait for a buffer before assessing smoothness. If an error appears, try another browser that supports the MP4 source. This player offers one 4K file and does not silently substitute a lower-quality encode, so the same source remains the basis for your comparison.

For uneven motion, repeat at the same video moment with demanding applications closed and a consistent power mode. In Windows, inspect Settings → System → Display → Advanced display for the selected refresh rate. On supported Macs, use System Settings → Displays → Refresh Rate. Compare again after one change; neither readout certifies panel Hz, HDR brightness or color accuracy.

References: MDN: video-frame callbacks · Windows refresh settings · Mac refresh settings.