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Why repeated audio conversion can reduce quality
Decoding and re-encoding a lossy file creates another generation of approximation. A larger output bitrate does not reverse the first loss.
Reviewed against current browser behavior and AudioFetcher test fixtures on July 28, 2026.
Key facts
MP3-to-MP3 and AAC-to-MP3 are lossy-to-lossy transcodes.
Lossless-to-lossy creates one delivery generation.
Lossless-to-lossless preserves decoded samples.
Metadata-only edits can often copy the audio stream without re-encoding.
Practical decisions
- Keep the earliest lossless source as the master.
- Create each delivery format directly from that master.
Measure the source before changing it. Codec, container, duration, channels, and intended playback environment are more useful than choosing a setting from its label alone.
Questions about Why repeated audio conversion can reduce quality
What is the short answer to "Why repeated audio conversion can reduce quality"?
Decoding and re-encoding a lossy file creates another generation of approximation. A larger output bitrate does not reverse the first loss.
Does the linked AudioFetcher tool upload my media?
The local tools linked from this article process selected media in the browser. Read each tool's limits before using a large or uncommon file.
What is the most important practical point?
Keep the earliest lossless source as the master.