From 2c8b77668772479b1ce02f321ae53f3220bf5a06 Mon Sep 17 00:00:00 2001
From: fkaelberer <o_0_o@gmx.de>
Date: Tue, 11 Mar 2014 09:14:59 +0100
Subject: [PATCH] update comments
---
src/core/arithmetic_decoder.js | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/src/core/arithmetic_decoder.js b/src/core/arithmetic_decoder.js
index e47547d84..fae2edbe6 100644
--- a/src/core/arithmetic_decoder.js
+++ b/src/core/arithmetic_decoder.js
@@ -17,8 +17,16 @@
'use strict';
-// Annex E. Arithmetic Coding
+/* This class implements the QM Coder decoding as defined in
+ * JPEG 2000 Part I Final Committee Draft Version 1.0
+ * Annex C.3 Arithmetic decoding procedure
+ * available at http://www.jpeg.org/public/fcd15444-1.pdf
+ *
+ * The arithmetic decoder is used in conjunction with context models to decode
+ * JPEG2000 and JBIG2 streams.
+ */
var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
+ // Table C-2
var QeTable = [
{qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1},
{qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0},
@@ -69,6 +77,7 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
{qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0}
];
+ // C.3.5 Initialisation of the decoder (INITDEC)
function ArithmeticDecoder(data, start, end) {
this.data = data;
this.bp = start;
@@ -86,6 +95,7 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
}
ArithmeticDecoder.prototype = {
+ // C.3.4 Compressed data input (BYTEIN)
byteIn: function ArithmeticDecoder_byteIn() {
var data = this.data;
var bp = this.bp;
@@ -111,6 +121,7 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
this.clow &= 0xFFFF;
}
},
+ // C.3.2 Decoding a decision (DECODE)
readBit: function ArithmeticDecoder_readBit(contexts, pos) {
// contexts are packed into 1 byte:
// highest 7 bits carry cx.index, lowest bit carries cx.mps
@@ -154,7 +165,7 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
cx_index = nmpsIcx;
}
}
- // renormD;
+ // C.3.3 renormD;
do {
if (this.ct === 0) {
this.byteIn();