/* motion.c, motion vector decoding */ /* 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 #include "global.h" /* private prototypes */ static void decode_motion_vector (MPEG2_Decoder *dec, int *pred, int r_size, int motion_code, int motion_residualesidual, int full_pel_vector); /* ISO/IEC 13818-2 sections 6.2.5.2, 6.3.17.2, and 7.6.3: Motion vectors */ void MPEG2_motion_vectors(MPEG2_Decoder *dec, int PMV[2][2][2], int dmvector[2], int motion_vertical_field_select[2][2], int s, int motion_vector_count, int mv_format, int h_r_size, int v_r_size, int dmv, int mvscale) { if (motion_vector_count==1) { if (mv_format==MV_FIELD && !dmv) { motion_vertical_field_select[1][s] = motion_vertical_field_select[0][s] = MPEG2_Get_Bits(dec, 1); } MPEG2_motion_vector(dec, PMV[0][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0); /* update other motion vector predictors */ PMV[1][s][0] = PMV[0][s][0]; PMV[1][s][1] = PMV[0][s][1]; } else { motion_vertical_field_select[0][s] = MPEG2_Get_Bits(dec, 1); MPEG2_motion_vector(dec, PMV[0][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0); motion_vertical_field_select[1][s] = MPEG2_Get_Bits(dec, 1); MPEG2_motion_vector(dec, PMV[1][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0); } } /* get and decode motion vector and differential motion vector for one prediction */ void MPEG2_motion_vector(MPEG2_Decoder *dec, int *PMV, int *dmvector, int h_r_size, int v_r_size, int dmv, /* MPEG-2 only: get differential motion vectors */ int mvscale, /* MPEG-2 only: field vector in frame pic */ int full_pel_vector) /* MPEG-1 only */ { int motion_code, motion_residual; /* horizontal component */ /* ISO/IEC 13818-2 Table B-10 */ motion_code = MPEG2_Get_motion_code(dec); motion_residual = (h_r_size!=0 && motion_code!=0) ? MPEG2_Get_Bits(dec, h_r_size) : 0; decode_motion_vector(dec, &PMV[0],h_r_size,motion_code,motion_residual,full_pel_vector); if (dmv) dmvector[0] = MPEG2_Get_dmvector(dec); /* vertical component */ motion_code = MPEG2_Get_motion_code(dec); motion_residual = (v_r_size!=0 && motion_code!=0) ? MPEG2_Get_Bits(dec, v_r_size) : 0; if (mvscale) PMV[1] >>= 1; /* DIV 2 */ decode_motion_vector(dec, &PMV[1],v_r_size,motion_code,motion_residual,full_pel_vector); if (mvscale) PMV[1] <<= 1; if (dmv) dmvector[1] = MPEG2_Get_dmvector(dec); } /* calculate motion vector component */ /* ISO/IEC 13818-2 section 7.6.3.1: Decoding the motion vectors */ /* Note: the arithmetic here is more elegant than that which is shown in 7.6.3.1. The end results (PMV[][][]) should, however, be the same. */ static void decode_motion_vector(MPEG2_Decoder *dec, int *pred, int r_size, int motion_code, int motion_residual, int full_pel_vector) /* MPEG-1 (ISO/IEC 11172-1) support */ { int lim, vec; lim = 16<> 1) : (*pred); if (motion_code>0) { vec+= ((motion_code-1)<=lim) vec-= lim + lim; } else if (motion_code<0) { vec-= ((-motion_code-1)<picture_structure==FRAME_PICTURE) { if (dec->top_field_first) { /* vector for prediction of top field from bottom field */ DMV[0][0] = ((mvx +(mvx>0))>>1) + dmvector[0]; DMV[0][1] = ((mvy +(mvy>0))>>1) + dmvector[1] - 1; /* vector for prediction of bottom field from top field */ DMV[1][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0]; DMV[1][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] + 1; } else { /* vector for prediction of top field from bottom field */ DMV[0][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0]; DMV[0][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] - 1; /* vector for prediction of bottom field from top field */ DMV[1][0] = ((mvx +(mvx>0))>>1) + dmvector[0]; DMV[1][1] = ((mvy +(mvy>0))>>1) + dmvector[1] + 1; } } else { /* vector for prediction from field of opposite 'parity' */ DMV[0][0] = ((mvx+(mvx>0))>>1) + dmvector[0]; DMV[0][1] = ((mvy+(mvy>0))>>1) + dmvector[1]; /* correct for vertical field shift */ if (dec->picture_structure==TOP_FIELD) DMV[0][1]--; else DMV[0][1]++; } }