diff options
author | Fabrice Bellard <fabrice@bellard.org> | 2001-07-22 14:18:56 +0000 |
---|---|---|
committer | Fabrice Bellard <fabrice@bellard.org> | 2001-07-22 14:18:56 +0000 |
commit | de6d9b6404bfd1c589799142da5a95428f146edd (patch) | |
tree | 75ae0cbb74bdfafb6f1a40922db111a103db3bcf /libavcodec/fdctref.c | |
parent | 1b58d58ddaf8a8c766a0353885ff504babed0453 (diff) | |
download | ffmpeg-streaming-de6d9b6404bfd1c589799142da5a95428f146edd.zip ffmpeg-streaming-de6d9b6404bfd1c589799142da5a95428f146edd.tar.gz |
Initial revision
Originally committed as revision 5 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/fdctref.c')
-rw-r--r-- | libavcodec/fdctref.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/libavcodec/fdctref.c b/libavcodec/fdctref.c new file mode 100644 index 0000000..5038e67 --- /dev/null +++ b/libavcodec/fdctref.c @@ -0,0 +1,120 @@ +/* fdctref.c, forward discrete cosine transform, double precision */ + +/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ + +/* + * Disclaimer of Warranty + * + * These software programs are available to the user without any license fee or + * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims + * any and all warranties, whether express, implied, or statuary, including any + * implied warranties or merchantability or of fitness for a particular + * purpose. In no event shall the copyright-holder be liable for any + * incidental, punitive, or consequential damages of any kind whatsoever + * arising from the use of these programs. + * + * This disclaimer of warranty extends to the user of these programs and user's + * customers, employees, agents, transferees, successors, and assigns. + * + * The MPEG Software Simulation Group does not represent or warrant that the + * programs furnished hereunder are free of infringement of any third-party + * patents. + * + * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, + * are subject to royalty fees to patent holders. Many of these patents are + * general enough such that they are unavoidable regardless of implementation + * design. + * + */ + +#include <math.h> + +// #include "config.h" + +#ifndef PI +# ifdef M_PI +# define PI M_PI +# else +# define PI 3.14159265358979323846 +# endif +#endif + +/* global declarations */ +void init_fdct (void); +void fdct (short *block); + +/* private data */ +static double c[8][8]; /* transform coefficients */ + +void init_fdct() +{ + int i, j; + double s; + + for (i=0; i<8; i++) + { + s = (i==0) ? sqrt(0.125) : 0.5; + + for (j=0; j<8; j++) + c[i][j] = s * cos((PI/8.0)*i*(j+0.5)); + } +} + +void fdct(block) +short *block; +{ + register int i, j; + double s; + double tmp[64]; + + for(i = 0; i < 8; i++) + for(j = 0; j < 8; j++) + { + s = 0.0; + +/* + * for(k = 0; k < 8; k++) + * s += c[j][k] * block[8 * i + k]; + */ + s += c[j][0] * block[8 * i + 0]; + s += c[j][1] * block[8 * i + 1]; + s += c[j][2] * block[8 * i + 2]; + s += c[j][3] * block[8 * i + 3]; + s += c[j][4] * block[8 * i + 4]; + s += c[j][5] * block[8 * i + 5]; + s += c[j][6] * block[8 * i + 6]; + s += c[j][7] * block[8 * i + 7]; + + tmp[8 * i + j] = s; + } + + for(j = 0; j < 8; j++) + for(i = 0; i < 8; i++) + { + s = 0.0; + +/* + * for(k = 0; k < 8; k++) + * s += c[i][k] * tmp[8 * k + j]; + */ + s += c[i][0] * tmp[8 * 0 + j]; + s += c[i][1] * tmp[8 * 1 + j]; + s += c[i][2] * tmp[8 * 2 + j]; + s += c[i][3] * tmp[8 * 3 + j]; + s += c[i][4] * tmp[8 * 4 + j]; + s += c[i][5] * tmp[8 * 5 + j]; + s += c[i][6] * tmp[8 * 6 + j]; + s += c[i][7] * tmp[8 * 7 + j]; + + block[8 * i + j] = (short)floor(s + 0.499999); +/* + * reason for adding 0.499999 instead of 0.5: + * s is quite often x.5 (at least for i and/or j = 0 or 4) + * and setting the rounding threshold exactly to 0.5 leads to an + * extremely high arithmetic implementation dependency of the result; + * s being between x.5 and x.500001 (which is now incorrectly rounded + * downwards instead of upwards) is assumed to occur less often + * (if at all) + */ + } +} |