- Lossless means that, digitally, regardless of the format the file is stored in, there is no loss of data.
- The raw digital music file format types in common use are AIFF and WAV.
- The most common compressed digital music file format types are FLAC and ALAC.
- FLAC and ALAC compress the file, much like Zip compresses a regular file, but more efficiently for audio information.
- FLAC has different levels of compression, trading off file size for the amount of processing power required to compress and decompress the file.
- On average, a lossless compressed file will be about 50-70% of its original size.
- When de-compressed, no data has been lost.
- The bit rate for a CD-quality AIFF or WAV file is 1411 kbps (kilo-bits-per-second).
- Lossy means that data is removed to make the file smaller and the sound is altered.
- The most common lossy compressed file types are MP3, AAC and OGG.
- Files are compressed by removing the data storing the least audible sounds first.
- This often means any sounds above 16kHz (depending on compression level) are removed, as in music, instruments only produce sounds up to about 12-14kHz for the most part, so a person with good hearing and good equipment might just be able to discern this, but only with effort.
- File sizes end up about 1/10th to 1/3rd the original size.
- Even after decompression, the data removed is still lost.
- The highest bit rate for lossy files is (usually) 320 kbps and the common bit rates are 128 kbps and 192 kbps. Compare this to the lossless figure above.