Transcoding
/trænsˈkoʊdɪŋ/ · noun · verb · compression
Converting media from one encoding to another — what every converter does.
In more detail
Transcoding decodes media from one format and re-encodes it into another — HEIC to JPG, WebP to PNG, and so on.
When the destination is lossy, transcoding introduces some quality loss, so it’s best done once from the original source.
Transcoding versus related operations
A full transcode decodes a media stream to an intermediate representation and encodes it with a destination codec. Remuxing simply moves existing encoded streams into a different container. Rewrapping is therefore faster and avoids quality loss, but it works only when the destination container supports the original codecs.
Resizing, changing frame rate, normalising audio, burning subtitles, and applying filters all require decoded media and usually lead to a new encode. A file-extension change alone does none of these things and cannot make an unsupported codec compatible.
How to minimise quality loss
Start with the original or highest-quality source, select a codec suited to the destination, and avoid unnecessary intermediate exports. If only the container is incompatible, remux rather than transcode whenever possible.
For lossy output, inspect difficult sections containing motion, texture, gradients, small text, or dense music. A higher bitrate or quality setting can reduce new artefacts but cannot restore information missing from the source. Keep the original after conversion.
Key points
- Transcoding decodes and re-encodes; remuxing changes only the container.
- Filters, resizing, and codec changes normally require a new encode.
- Use the best source and avoid repeated lossy transcoding to preserve quality.