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DAN2 Lossless Compression by Daniel Bienvenu aka NewColeco A variant of DAN1 Compression Format Based on LZ77 data compression, multiple offset sizes, unary code and elias gamma. The project started after Alekmaul remarks and test data during December 2016. Technical information Three (3) differences compared to DAN1: The set of 4 different sizes to encode offset values becomes { 1, 4, 8, max } where max value is set by the user. The capability to store sequences of literal bytes is removed. The END OF DATA code is 17 bits long instead of 18. The data format changed a little, making it incompatible with the original DAN1 format. The first bits is an unary code to set the maximum of bits for offset values ( 0 = 10 bits, 10 = 11 bits, 110 = 12 bits, etc.) The second byte is the first raw byte to copy as literal. The rest of the data format follows similar to DAN1 specifications, except there is no sequences of literals (RLE) and also the END code is shorter by 1 bit. Comparing DAN1 and DAN2 In term of speed, the compression and decompression are virtually the same speed as DAN1. In term of size, the decompression routine is slightly bigger than DAN1, +7 bytes according to my z80 data compression library. The expected improvement in compression ratio is only due to the possibility to adjust the maximum number of bits to encode offsets. Test samples from Exomizer test1.bin (audio wave file) Original: 202762 ZX7: 223933 DAN1: 204208 (sequences of raw bytes help to not blow up in size) DAN2 -m 16: 216898 Pletter: 221245 MegaLZ: 221136 Aplib aka APPACK: 219793 PUCrunch: N/A test2.bin (text file filled only with the letter q) Original: 196608 ZX7: 19 DAN1: 18 DAN2 -f -m 10: 18 Pletter: N/A *error during compression* MegaLZ: 2510 Aplib aka APPACK: 19 PUCrunch: N/A test3.bin (formatted text file with fields such as name and date) Original: 111261 ZX7: 52035 DAN1: 48103 DAN2 -m 16: 37048 Pletter: 44563 MegaLZ: 47052 Aplib aka APPACK: 37094 PUCrunch: N/A Test samples from Alekmaul Robee Blaster Title (Pattern, Color, and Name version) Original: 2024, 2024 and 768. Total 4816 ZX7: 970, 790 and 383. Total 2143 DAN1: 965, 793 and 385. Total 2143 DAN2 m -10: 947, 784 and 385. Total 2116 Pletter: 957, 787 and 385. Total 2129 MegaLZ: 972, 806 and 384. Total 2162 Aplib aka APPACK: 986, 806 and 384. Total 2176 PUCrunch -d -c0 -s: 940, 772 and 373. Total 2085 Robee Blaster Title (Pattern and Color only version) Original: 6144 and 6144. Total 12288 ZX7: 1257 and 793. Total 2049 DAN1: 1248 and 799. Total 2047 DAN2 -m 11: 1233 and 791. Total 2024 Pletter: 1259 and 795. Total 2054 MegaLZ: 1269 and 832. Total 2101 Aplib ka APPACK: 1273 and 825. Total 2098 PUCrunch -d -c0 -s: 1235 and 770. Total 2005 Test Sample Bitmap Graphic II Download DAN2 (EXE, SRC, ASM) version BETA-20170106 : dan2-beta-20170106.zip Change Log for version BETA-20170106: increased up to 16 bits max offset size value fixed bug with default max bits fixed bug occurring with test2.bin sample DAN2 (EXE, SRC, ASM) version BETA-20170101 : dan2-beta-20170101.zip * BUG FOUND , PLEASE DOWNLOAD NEWER VERSION *
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