decoder.c

代码实现了基于ARM7的MPEG-4视频解码器

//******************************************
//File name:  decoder.c
//Author:     Anna
//Date;
//******************************************
#include <assert.h>

#define DEC_MBC         45
#define DEC_MBR         36

#define INTRA			3

extern	int dc_store_lum[2*DEC_MBR+1][2*DEC_MBC+1];
extern	int ac_left_lum[2*DEC_MBR+1][2*DEC_MBC+1][7];
extern	int ac_top_lum[2*DEC_MBR+1][2*DEC_MBC+1][7];

extern	int dc_store_chr[2][DEC_MBR+1][DEC_MBC+1];
extern	int ac_left_chr[2][DEC_MBR+1][DEC_MBC+1][7];
extern	int ac_top_chr[2][DEC_MBR+1][DEC_MBC+1][7];

extern	int	modemap[DEC_MBR+1][DEC_MBC+2];
extern int	quant_store[DEC_MBR+1][DEC_MBC+1]; // [Review]
extern	int	MV[2][6][DEC_MBR+1][DEC_MBC+2];

extern unsigned char	*edged_ref[3],
									  *edged_for[3],
									  *frame_ref[3],
									  *frame_for[3],
									  *display_frame[3];
extern int	horizontal_size;
extern int	vertical_size;
extern int	chrom_width;
extern int	chrom_height;
extern int	mb_width;
extern int	mb_height;
extern int	coded_picture_width;
extern int	coded_picture_height;

extern void * mp4_edged_ref_buffers; 
extern void * mp4_edged_for_buffers; 
extern void *mp4_display_buffers; 

void initdecoder (int n)
{
  int i,j,cc;
  
// save_tables(mp4_tables);
 
  /*dc prediction border*/
  for (i = 0; i < (2*DEC_MBC+1); i++)
		dc_store_lum[0][i] = 1024;

	for (i = 1; i < (2*DEC_MBR+1); i++)
		dc_store_lum[i][0] = 1024;

	for (i = 0; i < (DEC_MBC+1); i++) {
		dc_store_chr[0][0][i] = 1024;
		dc_store_chr[1][0][i] = 1024;
	}

	for (i = 1; i < (DEC_MBR+1); i++) {
		dc_store_chr[0][i][0] = 1024;
		dc_store_chr[1][i][0] = 1024;
	}

  /*ac prediction border*/
  
  for (i = 0; i < (2*DEC_MBC+1); i++)
		for (j = 0; j < 7; j++)	{
			ac_left_lum[0][i][j] = 0;
			ac_top_lum[0][i][j] = 0;
		}

  for (i = 1; i < (2*DEC_MBR+1); i++)
		for (j = 0; j < 7; j++)	{
			ac_left_lum[i][0][j] = 0;
			ac_top_lum[i][0][j] = 0;
		}
		
	/* 
			[Review] too many computation to access to the 
			correct array value, better use two different
			pointer for Cb and Cr components
	*/
	for (i = 0; i < (DEC_MBC+1); i++)
		for (j = 0; j < 7; j++)	{
			ac_left_chr[0][0][i][j] = 0; 
			ac_top_chr[0][0][i][j] = 0;
			ac_left_chr[1][0][i][j] = 0;
			ac_top_chr[1][0][i][j] = 0;
		}

	for (i = 1; i < (DEC_MBR+1); i++)
		for (j = 0; j < 7; j++)	{
			ac_left_chr[0][i][0][j] = 0;
			ac_top_chr[0][i][0][j] = 0;
			ac_left_chr[1][i][0][j] = 0;
			ac_top_chr[1][i][0][j] = 0;
		}
	
		
		/* mode border */
	for (i = 0; i < mb_width + 1; i++) 
		modemap[0][i] = INTRA;
	for (i = 0; i < mb_height + 1; i++) {
		modemap[i][0] = INTRA;
		modemap[i][mb_width+1] = INTRA;
	}
	
	// edged forward and reference frame
   for (cc = 0; cc < 3; cc++)
  {
    if (cc == 0)
    {
			edged_ref[cc] = (unsigned char *) mp4_edged_ref_buffers;
			assert(edged_ref[cc]);//this can be ignored

			edged_for[cc] = (unsigned char *) mp4_edged_for_buffers;
			assert(edged_for[cc]);

        frame_ref[cc] = edged_ref[cc] + coded_picture_width * 32 + 32;
        frame_for[cc] = edged_for[cc] +coded_picture_width * 32 + 32;
    } 
    else
    {
			unsigned int offset;

			if (cc == 1) 
				offset = coded_picture_width * coded_picture_height;
			else 
				offset = coded_picture_width * coded_picture_height +
	  					 chrom_width * chrom_height;

			edged_ref[cc] = (unsigned char *) mp4_edged_ref_buffers + offset;
			assert(edged_ref[cc]);

			edged_for[cc] = (unsigned char *) mp4_edged_for_buffers + offset;
			assert(edged_for[cc]);

      frame_ref[cc] = edged_ref[cc] + chrom_width * 16 + 16;
      frame_for[cc] = edged_for[cc] + chrom_width * 16 + 16;
    }    
  }
  
  // display frame
	for (cc = 0; cc < 3; cc++) 
	{
		unsigned int offset;

		switch (cc) 
		{
		case 0:
			offset = 0;
			break;
		case 1:
			offset = horizontal_size * vertical_size;
			break;
		case 2:
			offset = (horizontal_size * vertical_size) + 
				((horizontal_size * vertical_size) >> 2);
			break;
		}
		
		display_frame[cc] = (unsigned char *) mp4_display_buffers + offset;
		//assert(display_frame[cc]);
	}  
}