Question 1

What is the difference between a video codec and a container?

Accepted Answer

The **codec** determines how the video is compressed; the **container** is the file format holding the compressed streams together. `.mp4` is a container — it tells you almost nothing about what is inside.

**The container** — MP4, MKV, MOV, AVI, WebM. It bundles the video stream, one or more audio streams, subtitles, chapters and metadata into a single file, and stores the information needed to keep them synchronised.

**The codec** — H.264, H.265/HEVC, AV1, VP9, ProRes. It defines the **compression algorithm**: how the video data is reduced in size, and how it must be decoded to play.

**Why this explains a common frustration.** A file may refuse to play, or play with no sound, despite having a familiar extension — because the container is supported but the **codec inside it is not**. The extension describes the box, not the contents, which is why "convert it to MP4" sometimes fixes nothing.

**The main video codecs:**

**H.264 (AVC)** — the universal compatibility baseline. Supported by essentially everything, hardware-accelerated everywhere, and less efficient than newer options.

**H.265 (HEVC)** — roughly half the file size at similar quality. Encumbered by **complex patent licensing**, which slowed adoption considerably and is why support is inconsistent.

**AV1** — royalty-free, developed by an industry consortium partly in response to HEVC's licensing. More efficient again, computationally demanding, and now widely used by streaming services.

**VP9**, its predecessor.

**ProRes and DNxHD** — editing codecs, much larger files, designed for fast decoding and repeated re-encoding rather than distribution.

**Audio codecs** sit alongside: AAC, MP3, Opus, FLAC, and lossless surround formats.

**Lossy versus lossless.** Almost all distribution codecs are **lossy** — data is permanently discarded. Re-encoding a lossy file loses more each time, which is why repeatedly re-uploaded video degrades visibly.

**Hardware acceleration** matters practically: a device with a dedicated decoder for a codec plays it efficiently; without one, software decoding drains battery and may stutter.

Question 2

What is bitrate, and why does it matter more than resolution?

Accepted Answer

Bitrate is how much data is used per second of video — and it frequently determines picture quality more than resolution does, which is why a 4K stream can look worse than a Blu-ray at 1080p. The

Question 3

Do Bluetooth codecs like aptX and LDAC actually matter?

Accepted Answer

A codec determines how audio is compressed for transmission over Bluetooth, and it matters — though less than headphone quality, fit and the source recording. Why compression is necessary. Bluetooth

Question 4

What is chroma subsampling, and why does text look bad over HDMI?

Accepted Answer

A compression technique that stores colour information at lower resolution than brightness, exploiting the fact that human vision is far more sensitive to brightness detail than to colour detail. It

Question 5

What do SD and microSD card speed ratings actually mean?

Accepted Answer

A confusing stack of overlapping rating systems, added over time and printed together on the same card — and the one that matters depends entirely on what you are doing with it. The ratings, in the

Question 6

Why are there so many HDMI versions and what is eARC?

Accepted Answer

Because each version raised the bandwidth available, and bandwidth determines what combination of resolution, frame rate, colour depth and audio a cable and port can carry. The main versions: HDMI

Question 7

What is the difference between Thunderbolt and USB4?

Accepted Answer

They are now closely related — USB4 was built on Thunderbolt 3's donated protocol — but Thunderbolt imposes stricter mandatory requirements, which is why two ports that look identical can behave very

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