Editing ATRAC (section)

=== ATRAC Advanced Lossless ===

'''ATRAC Advanced Lossless''' is a "scalable" lossless audio codec that records a lossy ATRAC3 or ATRAC3plus stream, and supplements it with a stream of correction information stored within the file itself that allows the original signal to be reproduced, if desired. A player/decoder can extract and use just the ATRAC3 or ATRAC3plus data, or it can combine that with the correction stream to perfectly reproduce the original audio information. This allows the file to be decoded as either lossless or lossy. It is implemented in such a way that allows the file size to be smaller than uncompressed or compressed versions of the same file. Compression is approximately 30–80% of the original file. Benefits of scalable compression include providing backward compatibility, such that older devices that are not AAL-aware can still have the ATRAC3 stream available for playback without understanding the AAL format, and faster transfer speed between portable audio devices and PC.<ref>{{Cite web|url=https://www.sony.net/Products/ATRAC3/tech/aal.html|title=Sony Global - ATRAC - ATRAC Advanced Lossless|website=www.sony.net}}</ref>

ATRAC Advanced Lossless is widely supported in older [[Walkman]] players and SonicStage version 4 or later. SonicStage 4 allows download of ATRAC Advanced Lossless to MiniDisc Players, [[PlayStation Portable]], and [[PlayStation 3]]. Recent Walkman players do not support ATRAC Advanced Lossless/ATRAC.

AAL's use of a "core" (lossy) and "residual" (correction) stream is similar to the idea behind [[Opus (audio format)|Opus]], [[MPEG-4 SLS]], [[DTS-HD Master Audio]], [[Dolby TrueHD]] and Ogg Vorbis [[bitrate peeling]]. In fact, AAL was the first to be released in the commercial market with this scheme for backward compatibility.

[[WavPack]] hybrid mode and [[OptimFROG]] DualStream are in the same category, but store the correction stream in a separate file.