File Formats
Audio Codecs Explained for Transcription
A plain-English guide to containers, codecs, compression, and why format names can be confusing.
Last updated: 2026-06-29 · 8 min read
Container and codec are different
A container is like a wrapper for the audio. A codec describes how the sound is encoded. For example, WebM and OGG are containers that may contain speech-friendly codecs.
Most users do not need to inspect codecs manually, but this distinction explains why two files with similar names can behave differently.
Compression affects speech detail
Compression makes files smaller by removing or simplifying audio information. Reasonable compression is usually fine for speech, but extreme compression can blur consonants and quiet words.
When you control the recording, choose a clear speech setting instead of the smallest possible file.
Recommendations
- Keep original files when possible.
- Use common formats such as MP3, M4A, WAV, OGG, OPUS, or WebM.
- If upload fails, export the audio again using a standard speech/audio setting.
Limitations
- Some files use unusual encoding despite having a familiar extension.
- Browser support can vary by device and operating system.