Audio Formats
FLAC, ALAC, AAC: what actually changes when you listen
A plain explanation of codecs, containers and file extensions — and which differences you can hear on a phone with everyday headphones.
The short answer
A codec decides how audio is compressed. A container decides how the compressed audio and its metadata are packaged. A file extension is only a label on the container. FLAC and ALAC are lossless codecs; AAC and MP3 are lossy. On a phone with typical headphones, the honest difference is smaller than the difference between two masterings of the same record.
Codec, container, extension
This is where most confusion starts.
| Layer | What it does | Examples |
|---|---|---|
| Codec | Compresses and decompresses audio | FLAC, ALAC, AAC, MP3 |
| Container | Packages audio plus metadata | M4A, MP4, MOV, WAV, AIFF |
| Extension | Names the container on disk | .m4a, .flac, .wav |
ALAC is the clearest example: it is almost always delivered inside an M4A container. So a .m4a file might contain AAC or ALAC, and only the codec inside tells you whether it is lossy or lossless.
Lossless versus lossy, without the folklore
Lossless codecs reconstruct the original samples exactly. Lossy codecs discard information that the encoder models as inaudible, which is why a well-encoded 256 kbps AAC file is much smaller and, for most listening situations, hard to distinguish.
What actually affects what you hear, roughly in order of impact:
- The mastering of the release you own.
- Your headphones or speakers, and how they are fitted.
- The listening environment.
- Any equalisation applied during playback.
- The codec, at reasonable bitrates.
That ordering is not an argument against lossless files. It is an argument for keeping your best copy and not re-encoding it repeatedly.
Storage: the practical trade
A three-minute track lands roughly around 20-30 MB as uncompressed WAV, 12-20 MB as FLAC or ALAC, and 5-7 MB as AAC at a high bitrate. On a device with fixed storage, that difference decides how much of the collection travels with you.
Practical rules
- Keep the highest-quality copy you own as your archive.
- Do not transcode a lossy file into a lossless format — it grows the file without recovering anything.
- Prefer embedded artwork over sidecar image files if you want artwork to survive a move.
- When a file will not play, check the codec inside the container before replacing the file.
Where OVO fits
OVO reads the common formats a personal collection is made of and shows what it found rather than hiding the detail. The supported formats page lists the containers and extensions we publish, with import and metadata notes for each.
