motion.cpp

/* 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 "global.h"
#include "getbit.h"

void motion_vector(int *PMV, int *dmvector, int h_r_size, int v_r_size,
	int dmv, int mvscale, int full_pel_vector);
__forceinline static void decode_motion_vector(int *pred, int r_size, int motion_code,
	int motion_residualesidual, int full_pel_vector);
__forceinline static int Get_motion_code(void);
__forceinline static int Get_dmvector(void);
extern void SetFaultFlag(int val);

/* ISO/IEC 13818-2 sections 6.2.5.2, 6.3.17.2, and 7.6.3: Motion vectors */
void motion_vectors(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] = Get_Bits(1);

		motion_vector(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] = Get_Bits(1);
		motion_vector(PMV[0][s],dmvector,h_r_size,v_r_size,dmv,mvscale,0);
		motion_vertical_field_select[1][s] = Get_Bits(1);
		motion_vector(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 motion_vector(int *PMV, int *dmvector, int h_r_size, int v_r_size,
				   int dmv, int mvscale, int full_pel_vector)
{
	int motion_code, motion_residual;

	/* horizontal component */
	/* ISO/IEC 13818-2 Table B-10 */
	motion_code = Get_motion_code();

	motion_residual = (h_r_size!=0 && motion_code!=0) ? Get_Bits(h_r_size) : 0;

	decode_motion_vector(&PMV[0],h_r_size,motion_code,motion_residual,full_pel_vector);

	if (dmv)
		dmvector[0] = Get_dmvector();

	/* vertical component */
	motion_code     = Get_motion_code();
	motion_residual = (v_r_size!=0 && motion_code!=0) ? Get_Bits(v_r_size) : 0;

	if (mvscale)
		PMV[1] >>= 1; /* DIV 2 */

	decode_motion_vector(&PMV[1],v_r_size,motion_code,motion_residual,full_pel_vector);

	if (mvscale)
		PMV[1] <<= 1;

	if (dmv)
		dmvector[1] = Get_dmvector();
}

/* 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(int *pred, int r_size, int motion_code,
								 int motion_residual, int full_pel_vector)
{
	int lim, vec;

	lim = 16<<r_size;
	vec = full_pel_vector ? (*pred >> 1) : (*pred);

	if (motion_code>0)
	{
		vec+= ((motion_code-1)<<r_size) + motion_residual + 1;
		if (vec>=lim)
			vec-= lim + lim;
	}
	else if (motion_code<0)
	{
		vec-= ((-motion_code-1)<<r_size) + motion_residual + 1;
		if (vec<-lim)
			vec+= lim + lim;
	}

	*pred = full_pel_vector ? (vec<<1) : vec;
}

/* ISO/IEC 13818-2 section 7.6.3.6: Dual prime additional arithmetic */
void Dual_Prime_Arithmetic(int DMV[][2],int *dmvector, int mvx,int mvy)
{
	if (picture_structure==FRAME_PICTURE)
	{
		if (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 (picture_structure==TOP_FIELD)
			DMV[0][1]--;
		else
			DMV[0][1]++;
	}
}

static int Get_motion_code()
{
	int code;

	if (Get_Bits(1))
		return 0;

	code = Show_Bits(9);
	if (code >= 64)
	{
		code >>= 6;
		Flush_Buffer(MVtab0[code].len);
		return (Get_Bits(1) ? -MVtab0[code].val : MVtab0[code].val);
	}

	if (code>=24)
	{
		code >>= 3;
		Flush_Buffer(MVtab1[code].len);
		return (Get_Bits(1) ? -MVtab1[code].val : MVtab1[code].val);
	}

	if (code >= 12)
	{
		code -= 12;
		Flush_Buffer(MVtab2[code].len);
		return (Get_Bits(1) ? -MVtab2[code].val : MVtab2[code].val);
	}

	SetFaultFlag(6);
	return 0;
}

/* get differential motion vector (for dual prime prediction) */
static int Get_dmvector()
{
	if (Get_Bits(1))
		return Get_Bits(1) ? -1 : 1;
	else
		return 0;
}