mpv/libmpcodecs/vd_msrle.c

#include <stdio.h>
#include <stdlib.h>

#include "config.h"
#include "mp_msg.h"

#include "vd_internal.h"

static vd_info_t info = {
	"Microsoft RLE decoder",
	"msrle",
	VFM_MSRLE,
	"A'rpi",
	"Mike Melanson",
	"native codec"
};

LIBVD_EXTERN(msrle)

// to set/get/query special features/parameters
static int control(sh_video_t *sh,int cmd,void* arg,...){
    return CONTROL_UNKNOWN;
}

// init driver
static int init(sh_video_t *sh){
    return mpcodecs_config_vo(sh,sh->disp_w,sh->disp_h,IMGFMT_BGR24);
}

// uninit driver
static void uninit(sh_video_t *sh){
}

//mp_image_t* mpcodecs_get_image(sh_video_t *sh, int mp_imgtype, int mp_imgflag, int w, int h);

#define FETCH_NEXT_STREAM_BYTE() \
    if (stream_ptr >= encoded_size) \
    { \
      mp_msg(MSGT_DECVIDEO, MSGL_WARN, \
        "MS RLE: stream ptr just went out of bounds (1)\n"); \
      return; \
    } \
    stream_byte = encoded[stream_ptr++];


void decode_msrle8(
  unsigned char *encoded,
  int encoded_size,
  unsigned char *decoded,
  int width,
  int height,
  unsigned char *palette_map,
  int bytes_per_pixel)
{
  unsigned char r, g, b;
  int stream_ptr = 0;
  unsigned char rle_code;
  unsigned char extra_byte;
  unsigned char stream_byte;
  int frame_size = width * height * bytes_per_pixel;
  int pixel_ptr = 0;
  int row_dec = width * bytes_per_pixel;
  int row_ptr = (height - 1) * row_dec;

/*
static int counter = 0;
int i;
printf ("run %d: ", counter++);
for (i = 0; i < 16; i++)
  printf (" %02X", encoded[i]);
printf ("\n");
for (i = encoded_size - 16; i < encoded_size; i++)
  printf (" (%d)%02X", i, encoded[i]);
printf ("\n");
*/

  while (row_ptr >= 0)
  {
    FETCH_NEXT_STREAM_BYTE();
    rle_code = stream_byte;
    if (rle_code == 0)
    {
      // fetch the next byte to see how to handle escape code
      FETCH_NEXT_STREAM_BYTE();
      if (stream_byte == 0)
      {
        // line is done, goto the next one
        row_ptr -= row_dec;
        pixel_ptr = 0;
      }
      else if (stream_byte == 1)
        // decode is done
        return;
      else if (stream_byte == 2)
      {
        // reposition frame decode coordinates
        FETCH_NEXT_STREAM_BYTE();
        pixel_ptr += stream_byte * bytes_per_pixel;
        FETCH_NEXT_STREAM_BYTE();
        row_ptr -= stream_byte * row_dec;
      }
      else
      {
        // copy pixels from encoded stream
        if ((row_ptr + pixel_ptr + stream_byte * bytes_per_pixel > frame_size) ||
            (row_ptr < 0))
        {
          mp_msg(MSGT_DECVIDEO, MSGL_WARN,
            "MS RLE: frame ptr just went out of bounds (1)\n");
          return;
        }

        rle_code = stream_byte;
        extra_byte = stream_byte & 0x01;
        if (stream_ptr + rle_code + extra_byte > encoded_size)
        {
          mp_msg(MSGT_DECVIDEO, MSGL_WARN,
            "MS RLE: stream ptr just went out of bounds (2)\n");
          return;
        }

        while (rle_code--)
        {
          r = palette_map[encoded[stream_ptr] * 4 + 2];
          g = palette_map[encoded[stream_ptr] * 4 + 1];
          b = palette_map[encoded[stream_ptr] * 4 + 0];
          stream_ptr++;
          decoded[row_ptr + pixel_ptr + 0] = b;
          decoded[row_ptr + pixel_ptr + 1] = g;
          decoded[row_ptr + pixel_ptr + 2] = r;
          pixel_ptr += bytes_per_pixel;
        }

        // if the RLE code is odd, skip a byte in the stream
        if (extra_byte)
          stream_ptr++;
      }
    }
    else
    {
      // decode a run of data
      if ((row_ptr + pixel_ptr + stream_byte * bytes_per_pixel > frame_size) ||
          (row_ptr < 0))
      {
        mp_msg(MSGT_DECVIDEO, MSGL_WARN,
          "MS RLE: frame ptr just went out of bounds (2)\n");
        return;
      }

      FETCH_NEXT_STREAM_BYTE();

      r = palette_map[stream_byte * 4 + 2];
      g = palette_map[stream_byte * 4 + 1];
      b = palette_map[stream_byte * 4 + 0];
      while(rle_code--)
      {
        decoded[row_ptr + pixel_ptr + 0] = b;
        decoded[row_ptr + pixel_ptr + 1] = g;
        decoded[row_ptr + pixel_ptr + 2] = r;
        pixel_ptr += bytes_per_pixel;
      }
    }
  }

  // one last sanity check on the way out
  if (stream_ptr < encoded_size)
    mp_msg(MSGT_DECVIDEO, MSGL_WARN,
      "MS RLE: ended frame decode with bytes left over (%d < %d)\n",
      stream_ptr, encoded_size);
}

// decode a frame
static mp_image_t* decode(sh_video_t *sh,void* data,int len,int flags){
    mp_image_t* mpi;
    if(len<=0) return NULL; // skipped frame
    
    mpi=mpcodecs_get_image(sh, MP_IMGTYPE_STATIC, MP_IMGFLAG_PRESERVE, 
	sh->disp_w, sh->disp_h);
    if(!mpi) return NULL;

    decode_msrle8(
        data,len, mpi->planes[0],
        sh->disp_w, sh->disp_h,
        (unsigned char *)sh->bih+40,
        mpi->bpp/8);
    
    return mpi;
}