1 /* motion.c, motion vector decoding */
3 /* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */
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33 /* private prototypes */
34 static void decode_motion_vector _ANSI_ARGS_((int *pred, int r_size, int motion_code,
35 int motion_residualesidual, int full_pel_vector));
37 /* ISO/IEC 13818-2 sections 6.2.5.2, 6.3.17.2, and 7.6.3: Motion vectors */
38 void motion_vectors(PMV,dmvector,
39 motion_vertical_field_select,s,motion_vector_count,mv_format,h_r_size,v_r_size,dmv,mvscale)
42 int motion_vertical_field_select[2][2];
43 int s, motion_vector_count, mv_format, h_r_size, v_r_size, dmv, mvscale;
45 if (motion_vector_count==1)
47 if (mv_format==MV_FIELD && !dmv)
49 motion_vertical_field_select[1][s] = motion_vertical_field_select[0][s] = Get_Bits(1);
53 printf("motion_vertical_field_select[][%d] (%d): %d\n",s,
54 motion_vertical_field_select[0][s],motion_vertical_field_select[0][s]);
59 motion_vector(PMV[0][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0);
61 /* update other motion vector predictors */
62 PMV[1][s][0] = PMV[0][s][0];
63 PMV[1][s][1] = PMV[0][s][1];
67 motion_vertical_field_select[0][s] = Get_Bits(1);
71 printf("motion_vertical_field_select[0][%d] (%d): %d\n",s,
72 motion_vertical_field_select[0][s],motion_vertical_field_select[0][s]);
75 motion_vector(PMV[0][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0);
77 motion_vertical_field_select[1][s] = Get_Bits(1);
81 printf("motion_vertical_field_select[1][%d] (%d): %d\n",s,
82 motion_vertical_field_select[1][s],motion_vertical_field_select[1][s]);
85 motion_vector(PMV[1][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0);
89 /* get and decode motion vector and differential motion vector
91 void motion_vector(PMV,dmvector,
92 h_r_size,v_r_size,dmv,mvscale,full_pel_vector)
97 int dmv; /* MPEG-2 only: get differential motion vectors */
98 int mvscale; /* MPEG-2 only: field vector in frame pic */
99 int full_pel_vector; /* MPEG-1 only */
101 int motion_code, motion_residual;
103 /* horizontal component */
104 /* ISO/IEC 13818-2 Table B-10 */
105 motion_code = Get_motion_code();
107 motion_residual = (h_r_size!=0 && motion_code!=0) ? Get_Bits(h_r_size) : 0;
112 if (h_r_size!=0 && motion_code!=0)
114 printf("motion_residual (");
115 Print_Bits(motion_residual,h_r_size,h_r_size);
116 printf("): %d\n",motion_residual);
122 decode_motion_vector(&PMV[0],h_r_size,motion_code,motion_residual,full_pel_vector);
125 dmvector[0] = Get_dmvector();
128 /* vertical component */
129 motion_code = Get_motion_code();
130 motion_residual = (v_r_size!=0 && motion_code!=0) ? Get_Bits(v_r_size) : 0;
135 if (v_r_size!=0 && motion_code!=0)
137 printf("motion_residual (");
138 Print_Bits(motion_residual,v_r_size,v_r_size);
139 printf("): %d\n",motion_residual);
145 PMV[1] >>= 1; /* DIV 2 */
147 decode_motion_vector(&PMV[1],v_r_size,motion_code,motion_residual,full_pel_vector);
153 dmvector[1] = Get_dmvector();
157 printf("PMV = %d,%d\n",PMV[0],PMV[1]);
161 /* calculate motion vector component */
162 /* ISO/IEC 13818-2 section 7.6.3.1: Decoding the motion vectors */
163 /* Note: the arithmetic here is more elegant than that which is shown
164 in 7.6.3.1. The end results (PMV[][][]) should, however, be the same. */
166 static void decode_motion_vector(pred,r_size,motion_code,motion_residual,full_pel_vector)
168 int r_size, motion_code, motion_residual;
169 int full_pel_vector; /* MPEG-1 (ISO/IEC 11172-1) support */
174 vec = full_pel_vector ? (*pred >> 1) : (*pred);
178 vec+= ((motion_code-1)<<r_size) + motion_residual + 1;
182 else if (motion_code<0)
184 vec-= ((-motion_code-1)<<r_size) + motion_residual + 1;
188 *pred = full_pel_vector ? (vec<<1) : vec;
192 /* ISO/IEC 13818-2 section 7.6.3.6: Dual prime additional arithmetic */
193 void Dual_Prime_Arithmetic(DMV,dmvector,mvx,mvy)
195 int *dmvector; /* differential motion vector */
196 int mvx, mvy; /* decoded mv components (always in field format) */
198 if (picture_structure==FRAME_PICTURE)
202 /* vector for prediction of top field from bottom field */
203 DMV[0][0] = ((mvx +(mvx>0))>>1) + dmvector[0];
204 DMV[0][1] = ((mvy +(mvy>0))>>1) + dmvector[1] - 1;
206 /* vector for prediction of bottom field from top field */
207 DMV[1][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0];
208 DMV[1][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] + 1;
212 /* vector for prediction of top field from bottom field */
213 DMV[0][0] = ((3*mvx+(mvx>0))>>1) + dmvector[0];
214 DMV[0][1] = ((3*mvy+(mvy>0))>>1) + dmvector[1] - 1;
216 /* vector for prediction of bottom field from top field */
217 DMV[1][0] = ((mvx +(mvx>0))>>1) + dmvector[0];
218 DMV[1][1] = ((mvy +(mvy>0))>>1) + dmvector[1] + 1;
223 /* vector for prediction from field of opposite 'parity' */
224 DMV[0][0] = ((mvx+(mvx>0))>>1) + dmvector[0];
225 DMV[0][1] = ((mvy+(mvy>0))>>1) + dmvector[1];
227 /* correct for vertical field shift */
228 if (picture_structure==TOP_FIELD)