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--- atrac3p:start [2009/11/14 17:57] – megadiscman
+++ atrac3p:start [2010/07/23 18:20] – Link multimedia.cx megadiscman
@@ Line 1: / Line 1: @@
 ===== ATRAC3+ format documentation =====
-ATRAC3+ is a hybrid subband codec like MP3. The signal is split into 16 bands, that are mostly encoded in the frequency domain. Some of the low frequency bands are split themself into smaller parts, customarily called //bandlets//, to a total of 32 bandlets. The purpose of the bandlets is that each bandlet has its own quantizer. The synthesis of ATRAC3+ sound data consists of:
+This is not the only ATRAC3+ documentation that floats around in the internet. A mostly independently derived specification can be found at [[http://wiki.multimedia.cx/index.php?title=ATRAC3plus]].
-  * [[bandlet joint stereo coefficient cloning]]
+==== intro =====
-  * [[bandlet dequantization]]
+ATRAC3+ is a hybrid subband codec like MP3. The signal is split into 16 bands, each band is then divided into two parts: A superposition of sinusodial tones and the spectral residue that is encoded in the frequency domain. For the frequency-domain encoding, some of the low frequency bands are split themself into smaller parts, called //[[ATRAC spectrum anatomy|quantization units]]//, to a total of 32 quantization units. The purpose of the quantization unit is that each unit has its own quantization parameters.
-  * [[band dithering]]
+ATRAC3+ can have more than 2 channels - in that case more than one substream is present. This case is not described here.
+==== Parsing ====
+  * First bit must be zero
+  * Array of blocks follows, each block:
+     * two bits type followed by data
+        * type 0 = single channel [[substream data]]
+        * type 1 = dual channel (stereo) [[substream data]]
+        * type 2 = non-audio data (ignored)
+        * type 3 = end of data marker
+==== Synthesis ====
+  * [[quantization unit joint stereo coefficient cloning]]
+  * [[quantization unit dequantization]]
+  * [[band frequency domain dithering]]
   * [[band joint stereo post processing]]
-and much more.
+  * [[muting]]
+  * [[band IMDCT]]
+  * [[band envelope processing]]
+  * [[band tone adding]]
+  * [[time domain dithering]]
+  * [[final band combination (IMDCT + FIR filtering)]]