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Drop one FLAC or two hundred. Batch conversion is not a paid feature here.
A lossless library has to work in Apple Music, on an iPhone or in a Mac-based workflow that ignores FLAC.
The FLAC is decoded to PCM and re-encoded as ALAC. Both are lossless, so the audio is bit-identical before and after, and only the container and the entropy coding change.
The file size changes slightly, usually a few percent larger for ALAC, because the two codecs predict differently. Anyone reporting a big size difference is comparing different source material, not codec efficiency.
None. Decode either format and the samples are identical.
Vorbis comments map onto MP4 atoms reasonably well, though obscure custom tags can be dropped. Embedded artwork survives.
Drop one FLAC or two hundred. Batch conversion is not a paid feature here.
ALAC File is lossless, so nothing is thrown away in the conversion.
Converted and deleted the moment it finishes. Never written to permanent storage.