ATRAC3plus
- Format tag: uses WAVE_FORMAT_EXTENSIBLE with the "SubFormat" field set to the following GUID: E923AABF-CB58-4471-A119-FFFA01E4CE62
- Company: Sony
- Samples:
- Stored in: WAV and Oma/Omg containers.
- Official information: http://www.sony.net/Products/ATRAC3/tech/atrac3plus.html
ATRAC3plus introduction
ATRAC3plus is a proprietary compression algorithm for audio developed by Sony. As in the case of ATRAC3 ATRAC3plus represents the next generation of the ATRAC codec introduced in 1992 with the MiniDisc. Common use of that codec is in nowel Minidisc players and Portable Playstations made by Sony.
Streams coded with ATRAC3plus are usually stored either in the WAV container (those files have the ".at3" extension though) or in the Sony's proprietary Oma/Omg container. In the case of the WAV container the undocumented GUID:
E923AABF-CB58-4471-A119-FFFA01E4CE62
is used in order to indicate the ATRAC3plus codec.
There is very limited number of software products supporting encoding/decoding of the ATRAC3plus streams; most of them are unfortunately available for Microsoft Windows only. Those are:
- Sony's own SonicStage software (Windows only)
- ATRAC Codec Plugin for Sony Media Software (Windows only)
- Sonic Studio's expensive N-code plugin for professionals (available for Windows and Mac OS X)
There is a multi-channel version of ATRAC3plus called "ATRAC-X".
ATRAC3plus technical documentaion
Supported bitrates
ATRAC3plus operates on fixed bitrates only. The following bitrates are supported:
bitrate frame size (stereo) ------------- ------------------- 48 Kbps 280 bytes 64 Kbps 376 bytes 96 Kbps 560 bytes 128 Kbps 744 bytes 160 Kbps 936 bytes 192 Kbps 1120 bytes 256 Kbps 1488 bytes 320 Kbps 1864 bytes 352 Kbps 2048 bytes
Coding techniques
ATRAC3 is a hybrid subband/MDCT codec like MP3. The signal is split into 16 subbands using Quadrature Mirror Filter before MDCT and bit allocation.