vidpickr

Glossary · workflow

What is Transcoding?

Transcoding is the process of decoding a compressed media file and re-encoding it into a different codec, container, bitrate, or resolution. It is always lossy for lossy source codecs — every transcode adds a small amount of quality loss on top of the original encoding.

Also called:transcode · re-encode · remux vs transcode

Transcoding is what happens when a video service "converts" your file. The original codec output is decoded back to raw frames (lossless step) and then re-encoded into the target codec (lossy step, even at high bitrates).

The lossy step is the issue. If you upload a 720p H.264 file at 5 Mbps and YouTube transcodes it to 720p VP9 at 2 Mbps, the result has two layers of compression artifacts stacked. The new file is smaller and cheaper to deliver, but it's never visually identical to the input.

Compare this with muxing (lossless: just re-wraps existing data) and transmuxing (lossless: changes container without touching codec data). For YouTube downloads, the goal is usually muxing — combining the served video and audio into a single MP4 with no transcode. VidPickr does this; some "MP4 converter" tools transcode unnecessarily and degrade the file.

Common questions

Is downloading from YouTube transcoding?
Not in VidPickr's case. We mux the served video and audio bytes into an MP4 without re-encoding. Some other tools transcode to "convert" the file, which both takes longer and produces a slightly worse result.
When does transcoding make sense?
When the source codec doesn't play on the target device (HEVC video on a 2015 Android), when the file needs to fit a strict size budget, or when you want to ship the file to a publishing platform with codec restrictions.

Related terms

Mux (muxing)

Muxing is the process of combining separate audio and video streams into a single container file (MP4, MKV, WebM).

Codec

A codec is the algorithm that encodes (compresses) and decodes raw audio or video into a smaller stream.

Container (file format)

A container is the file format that wraps one or more audio and video streams into a single file.

Bitrate

Bitrate is the amount of data a video or audio stream carries per second, measured in bits per second (bps) or kilobits (kbps) and megabits (Mbps).

VidPickr is a free, browser-based YouTube downloader. Every term in this glossary either describes how YouTube delivers video or why your downloads behave the way they do. Try the downloader →