Question 1

How does Aspect Ratio (e.g. 2.39:1 Cinema Scope) change video file size?

Accepted Answer

File size is mathematically determined by bitrate and duration. However, aspect ratio directly dictates how many active pixels receive data. A 2.39:1 widescreen cinema movie cropped to 3840x1607 has 25.6% fewer pixels than an uncropped 16:9 (3840x2160) frame. Because the encoder does not have to compress black letterbox bars, encoding at 6.4 Mbps gives a 2.39:1 movie 25% higher visual data density per pixel than 16:9 at the exact same file size!

Question 2

Why does 24 fps look clearer than 60 fps at the exact same bitrate?

Accepted Answer

Temporal bit budgeting. At 6,000 kbps, 24 fps gets 250 kilobits per frame. At 60 fps, the encoder only gets 100 kilobits per frame — an immediate 60% loss in data available per frame. In high-motion action scenes or complex textures, 60 fps will suffer noticeable macroblocking unless you increase your bitrate accordingly.

Question 3

Why does a 1h 55m 4K movie at 6.4 Mbps calculate to approximately 5.2 GB?

Accepted Answer

At 1 hour and 55 minutes (6,900 seconds), 6.4 Mbps transfers 44,160 megabits of video. Adding a 192 kbps audio track adds 1,324 megabits. Dividing the 45,484 megabits by 8 yields ~5,685 MB, which equals 5.29 GiB in Windows binary notation or 5.17 GB in decimal notation when accounting for tight stream muxing.

Question 4

Why does Windows File Explorer show a smaller file size (GiB) than my hard drive (GB)?

Accepted Answer

Windows File Explorer calculates sizes using binary Gibibytes (1 GiB = 1024^3 = 1,073,741,824 bytes). Storage manufacturers, macOS, and video standards use decimal Gigabytes (1 GB = 1000^3 = 1,000,000,000 bytes). A 5.0 GB movie will read as ~4.65 GiB on Windows, even though zero bytes are missing.

Question 5

What is Bits-Per-Pixel (bpp) and why is it the gold standard for quality?

Accepted Answer

Bits-per-pixel measures the raw data allocated to each individual pixel on every frame (bps / [width * height * fps]). A bpp of 0.03 to 0.06 is the sweetspot for modern HEVC (H.265) and AV1 encoders. Below 0.025, dark scenes will start showing color banding and blocking artifacts.

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