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--- atrac3p:serialized_bandlet_tree_choice_info [2009/11/23 18:39] – megadiscman
+++ atrac3p:serialized_bandlet_tree_choice_info [2010/07/23 17:01] (current) – delete renamed page (bandlet -> QU) megadiscman
@@ Line 1: / Line 1: @@
-===== Serialized bandlet tree IDs =====
-The frequency space data of the bandlets is generally Huffman encoded. There are two tree sets, which will be called tree set A and tree set B. Each of the tree sets consists of 8 trees for each quantizer (except quantizer 0 which means that no data is present). Some of the trees are duplicate.
-As opposed to the bandlet levels, which are stored for all bandlets up to the last bandlet with a non-zero quantizer, Tree IDs are not stored for bandlets with a zero quantizer //at all//, even if the zero quantized bandlet is followed by a bandlet with a non-zero quantizer.
-The tree choice may either be complete (each bandlet chooses one of the eight trees for it's quantizer) or restricted (each bandlet chooses one of the four most common trees for it's quantizer). The choice between complete or restricted selection is global for the whole substream, not just for the channel! Thus the bit is not descibed here, in the per-channel tree choice data, but in the parent page [[substream data]].
-Another catch is that the Tree ID is reused as a joint stereo flag. If the quantizer is zero for the slave channel, but non-zero for the master channel, the slave channel has (contradicting to the simplified introduction) still one bit stored. If this bit is zero, The data from the master channel is reused, if this bit is one, the zero quantizer is taken literally (as it is always for the master channel) and the frequency data is completely zero.
-If bandlet specific info is given at all (i.e. not mode 3 on master channel), then a bit indicates whether tree IDs are stored for all bandlets that need them, or only for the some first bandlets (number given) and the remaining tree IDs are implicitly zero.
-==== Encoding Modes ====
-=== Mode 0: direct encoding ===
-The value to encode for each bandlet is directly encoded as binary number. It's a three bit number for complete tree access, a two-bit-number for restricted tree access or a one-bit joint-stereo flag.
-===== Encoding =====
-  * 1 bit: If set, use tree set B, if clear, use tree set A
-  * 2 bit: Ecnoding mode
-  * In all encodings modes except 3/master:
-    * 1 bit: enable zero expansion
-    * if zero expansion enabled
-      * 5 bit: number of highes bandlet with non-zero tree ID
-==== Encoding mode 0: direct encoding ====
-  * for each explicit bandlet:
-     * non-zero quant, full IDs: 3 bits tree ID
-     * non-zero quant, common trees: 2 bits common tree number
-     * zero quant, master non-zero: 1 bit "don't copy" flag