The shortest DVD decoding program in the world (<0.5k)

Two students of the Tianshu Institute of Technology prepare the shortest DVD decoding program in the world, and this record is recently broken by a programmer named Charles M Hannum, and the decoding program he wrote is only 442 bytes, and The seven-line Perl decoding program is 472 bytes.

Hannum's C program is called: EFDTT, it is said that its speed is quite fast, can reach 21.5Mbps, even if it does not need to be specifically performed in decoding, such speed makes the program to convert data to moving images Do not affect the decoding process of MPEG 2 at all.

Compared to two equipped decoding programs, the former supports instant decoding and playback, but it is said that its output playback occasion occasionally unstable. Hannum procedures support smooth playback.

The following is the source code of this program:

/ * EFDTT.C Author: Charles M. Hannum * // * usage is: cat title-key scrambed.vob | EFDTT> CLEAR.VOB * /

#define k (i) (x [i] ^ s [i 84]) << unsigned char x [5], y, z, s [2048]; main (n) {for (Read (0, x, 5); READ (0, s, n = 2048); Write (1, s, n)) IF (S [Y = S [13]% 8 20] / 16% 4 == 1) {INT i = K (1) 17 ^ 256 k (0) 8, K = K (2) 0, J = k (4) 17 ^ k (3) 9 ^ k * 2-k% 8 ^ 8, a = 0, B = 0, c = 26; for (s [y] - = 16; - C; I / = 2, j / = 2) a = a * 2 ^ I & 1, b = b * 2 ^ J & 1; for ( J = 127; j y) a ^ = a >> 14, a = a >> 8 ^ (y = a ^ a * 8 ^ a << 6) << 9 , B = B >> 8 ^ (z = b ^ b / 8 ^ b >> 4 ^ b >> 12) << 17, i = s [j], i = "7WO ~ 'g_ / 216" [I & 7 ] 2 ^ "CR3SFW6V; * K > / n." [I >> 4] * 2 ^ i * 257/8, s [j] = i ^ (i & i * 2 & 34) * 6 ^ Z C ~ Y; }