/* subspic.c, 幀緩存程序 */#include <stdio.h>#include <stdlib.h>#include <fcntl.h>#include "config.h"#include "global.h"/* private prototypes*/static void Read_Frame _ANSI_ARGS_((char *filename,   unsigned char *frame_buffer[], int framenum));static void Copy_Frame _ANSI_ARGS_((unsigned char *src, unsigned char *dst,   int width, int height, int parity, int incr));static int Read_Components _ANSI_ARGS_ ((char *filename,   unsigned char *frame[3], int framenum));static int Read_Component _ANSI_ARGS_ ((char *fname, unsigned char *frame,   int width, int height));static int Extract_Components _ANSI_ARGS_ ((char *filename,  unsigned char *frame[3], int framenum));/* substitute frame buffer routine */void Substitute_Frame_Buffer (bitstream_framenum, sequence_framenum)int bitstream_framenum;int sequence_framenum;{  /* static tracking variables */  static int previous_temporal_reference;  static int previous_bitstream_framenum;  static int previous_anchor_temporal_reference;  static int previous_anchor_bitstream_framenum;  static int previous_picture_coding_type;  static int bgate;    /* local temporary variables */  int substitute_display_framenum;#ifdef DEBUG  printf("SUB: seq fn(%d) bitfn(%d) tempref(%d) picstr(%d) type(%d)\n",     sequence_framenum, bitstream_framenum, temporal_reference,     picture_structure, picture_coding_type);#endif  /* we don't substitute at the first picture of a sequence */  if((sequence_framenum!=0)||(Second_Field))  {    /* only at the start of the frame */    if ((picture_structure==FRAME_PICTURE)||(!Second_Field))    {      if(picture_coding_type==P_TYPE)      {        /* the most recently decoded reference frame needs substituting */        substitute_display_framenum = bitstream_framenum - 1;                Read_Frame(Substitute_Picture_Filename, forward_reference_frame,           substitute_display_framenum);      }      /* only the first B frame in a consequitve set of B pictures         loads a substitute backward_reference_frame since all subsequent         B frames predict from the same reference pictures */      else if((picture_coding_type==B_TYPE)&&(bgate!=1))      {        substitute_display_framenum =           (previous_temporal_reference - temporal_reference)             + bitstream_framenum - 1;        Read_Frame(Substitute_Picture_Filename, backward_reference_frame,           substitute_display_framenum);      }    } /* P fields can predict from the two most recently decoded fields, even         from the first field of the same frame being decoded */    else if(Second_Field && (picture_coding_type==P_TYPE))    {      /* our favourite case: the IP field picture pair */      if((previous_picture_coding_type==I_TYPE)&&(picture_coding_type==P_TYPE))      {        substitute_display_framenum = bitstream_framenum;      }      else /* our more generic P field picture pair */      {        substitute_display_framenum =           (temporal_reference - previous_anchor_temporal_reference)             + bitstream_framenum - 1;      }      Read_Frame(Substitute_Picture_Filename, current_frame, substitute_display_framenum);    }#ifdef DEBUG    else if((picture_coding_type!=B_TYPE)||(picture_coding_type!=D_TYPE))    {      printf("NO SUBS FOR THIS PICTURE\n");    }#endif  }  /* set b gate so we don't redundantly load next time around */  if(picture_coding_type==B_TYPE)    bgate = 1;  else    bgate = 0;  /* update general tracking variables */  if((picture_structure==FRAME_PICTURE)||(!Second_Field))  {    previous_temporal_reference  = temporal_reference;    previous_bitstream_framenum  = bitstream_framenum;  }    /* update reference frame tracking variables */  if((picture_coding_type!=B_TYPE) &&     ((picture_structure==FRAME_PICTURE)||Second_Field))  {    previous_anchor_temporal_reference  = temporal_reference;    previous_anchor_bitstream_framenum  = bitstream_framenum;  }  previous_picture_coding_type = picture_coding_type;}/* Note: fields are only read to serve as the same-frame reference for    a second field */static void Read_Frame(fname,frame,framenum)char *fname;unsigned char *frame[];int framenum;{  int parity;  int rerr = 0;  int field_mode;  if(framenum<0)    printf("ERROR: framenum (%d) is less than zero\n", framenum);  if(Big_Picture_Flag)    rerr = Extract_Components(fname, substitute_frame, framenum);  else    rerr = Read_Components(fname, substitute_frame, framenum);  if(rerr!=0)  {    printf("was unable to substitute frame\n");  }  /* now copy to the appropriate buffer */  /* first field (which we are attempting to substitute) must be     of opposite field parity to the current one */  if((Second_Field)&&(picture_coding_type==P_TYPE))  {    parity      = (picture_structure==TOP_FIELD ? 1:0);          field_mode  = (picture_structure==FRAME_PICTURE ? 0:1);  }  else  {    /* Like frame structued pictures, B pictures only substitute an entire frame        since both fields always predict from the same frame (with respect        to forward/backwards directions) */    parity = 0;    field_mode = 0;  }  Copy_Frame(substitute_frame[0], frame[0], Coded_Picture_Width,     Coded_Picture_Height, parity, field_mode);    Copy_Frame(substitute_frame[1], frame[1], Chroma_Width, Chroma_Height,     parity, field_mode);    Copy_Frame(substitute_frame[2], frame[2], Chroma_Width, Chroma_Height,    parity, field_mode);#ifdef VERBOSE  if(Verbose_Flag > NO_LAYER)    printf("substituted %s %d\n",      (field_mode ? (parity?"bottom field":"bottom field"):"frame"), framenum);#endif}static int Read_Components(filename, frame, framenum) char *filename;unsigned char *frame[3];int framenum;{  int err = 0;  char outname[FILENAME_LENGTH];  char name[FILENAME_LENGTH];  sprintf(outname,filename,framenum);  sprintf(name,"%s.Y",outname);  err += Read_Component(name, frame[0], Coded_Picture_Width,     Coded_Picture_Height);  sprintf(name,"%s.U",outname);  err += Read_Component(name, frame[1], Chroma_Width, Chroma_Height);  sprintf(name,"%s.V",outname);  err += Read_Component(name, frame[2], Chroma_Width, Chroma_Height);  return(err);}static int Read_Component(Filename, Frame, Width, Height)char *Filename;unsigned char *Frame;int Width;int Height;{  int Size;  int Bytes_Read;  int Infile;  Size = Width*Height;#ifdef DEBUG  printf("SUBS: reading %s\n", filename);#endif  if(!(Infile=open(Filename,O_RDONLY|O_BINARY))<0)  {    printf("ERROR: unable to open reference filename (%s)\n", Filename);	return(-1);  }  Bytes_Read = read(Infile, Frame, Size);    if(Bytes_Read!=Size)  {    printf("was able to read only %d bytes of %d of file %s\n",      Bytes_Read, Size, Filename);  }   close(Infile);   return(0);}/* optimization: do not open the big file each time. Open once at start   of decoder, and close at the very last frame *//* Note: "big" files were used in E-mail exchanges almost exclusively by the    MPEG Committee's syntax validation and conformance ad-hoc groups from    the year 1993 until 1995 */static int Extract_Components(filename, frame, framenum) char *filename;unsigned char *frame[3];int framenum;{/*  int err = 0; */  FILE *fd;  int line;  int size, offset;  if (!(fd = fopen(filename,"rb")))  {    sprintf(Error_Text,"Couldn't open %s\n",filename);    return(-1);  }  /* compute size of each frame (in bytes) */  size = (Coded_Picture_Width*Coded_Picture_Height);  if(chroma_format==CHROMA444)    size = (size * 3);  else if(chroma_format==CHROMA422)    size = (size * 2);  else if(chroma_format==CHROMA420)    size = ((size*3)>>1);  else    printf("ERROR: chroma_format (%d) not recognized\n", chroma_format);  /* compute distance into "big" file */  offset = size*framenum;#ifdef DEBUG  printf("EXTRACTING: frame(%d) offset(%d), size (%d) from %s\n",     framenum, offset, size, filename);#endif  /* seek to location in big file where desired frame begins */  /* note: this offset cannot exceed a few billion bytes due to the */  /*       obvious limitations of 32-bit integers */  fseek(fd, offset, 0);  /* Y  */  for (line=0; line<Coded_Picture_Height; line++)  {    fread(frame[0]+(line*Coded_Picture_Width),1,Coded_Picture_Width,fd);  }  /* Cb */  for (line=0; line<Chroma_Height; line++)  {    fread(frame[1]+(line*Chroma_Width),1,Chroma_Width,fd);  }  /* Cr */  for (line=0; line<Chroma_Height; line++)  {    fread(frame[2]+(line*Chroma_Width),1,Chroma_Width,fd);  }  fclose(fd);  return(0);}static void Copy_Frame(src, dst, width, height, parity, field_mode)unsigned char *src;unsigned char *dst;int width;int height;int parity;        /* field parity (top or bottom) to overwrite */int field_mode;    /* 0 = frame, 1 = field                      */{  int row, col;  int s, d;  int incr;  s = d = 0;#ifdef DEBUG  printf("COPYING (w=%d, h=%d, parity=%d, field_mode=%d)\n",    width,height,parity,field_mode);#endif /* DEBUG */  if(field_mode)  {    incr = 2;    if(parity==0)      s += width;  }  else  {    incr = 1;  }  for(row=0; row<height; row+=incr)   {    for(col=0; col<width; col++)    {      dst[d+col] = src[s+col];    }        d += (width*incr);    s += (width*incr);  }}