imported from xine, generalized, created header file, all tables moved to

svq1_cb.h (was: svq1_codebooks.h)
TODO: use libavcodec's MC and bit parsing routines, maybe VLC too,
finally move the whole decoder to libavcodec


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@6506 b3059339-0415-0410-9bf9-f77b7e298cf2

1 files changed, 753 insertions, 0 deletions

diff --git a/libmpcodecs/native/svq1.c b/libmpcodecs/native/svq1.c
new file mode 100644
index 0000000000..e3108e00e7
--- /dev/null
+++ b/libmpcodecs/native/svq1.c
@@ -0,0 +1,753 @@
+/* 
+ * Copyright (C) 2002 the xine project
+ * 
+ * This file is part of xine, a unix video player.
+ * 
+ * xine is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * xine is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
+ *
+ * $Id$
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "bswap.h"
+
+/* variable length (bit) code */
+typedef struct vlc_code_s {
+  int16_t	 value	:10,
+		 length	:6;
+} vlc_code_t;
+
+#define VIDEOBUFSIZE	128 * 1024
+
+#define MEDIAN(a,b,c)	((a < b != b >= c) ? b : ((a < c != c > b) ? c : a))
+
+#include "svq1.h"
+#include "svq1_cb.h"
+
+/* memory bit stream */
+typedef struct bit_buffer_s {
+  uint8_t	*buffer;
+  uint32_t	 bitpos;
+} bit_buffer_t;
+
+/* standard video sizes */
+static struct { int width; int height; } frame_size_table[8] = {
+  { 160, 120 }, { 128,  96 }, { 176, 144 }, { 352, 288 },
+  { 704, 576 }, { 240, 180 }, { 320, 240 }, {  -1,  -1 }
+};
+
+
+static uint32_t get_bits (bit_buffer_t *bitbuf, int count) {
+  uint32_t result;
+
+  /* load 32 bits of data (byte-aligned) */
+  result   = be2me_32 (*((uint32_t *) &bitbuf->buffer[bitbuf->bitpos >> 3]));
+
+  /* compensate for sub-byte offset */
+  result <<= (bitbuf->bitpos & 0x7);
+
+  /* flush num bits */
+  bitbuf->bitpos += count;
+
+  /* return num bits */
+  return result >> (32 - count);
+}
+
+/*
+ * Return next 32 bits (left aligned).
+ */
+static uint32_t get_bit_cache(bit_buffer_t *bitbuf) {
+  uint32_t result;
+
+  /* load 32 bits of data (byte-aligned) */
+  result   = be2me_32 (*((uint32_t *) &bitbuf->buffer[bitbuf->bitpos >> 3]));
+
+  /* compensate for sub-byte offset */
+  result <<= (bitbuf->bitpos & 0x7);
+
+  return result;
+}
+
+static int decode_svq1_block (bit_buffer_t *bitbuf, uint8_t *pixels, int pitch, int intra) {
+  uint32_t    bit_cache;
+  vlc_code_t *vlc;
+  uint8_t    *list[63];
+  uint32_t   *dst;
+  uint32_t   *codebook;
+  int	      entries[6];
+  int	      i, j, m, n;
+  int	      mean, stages;
+  int	      x, y, width, height, level;
+  uint32_t    n1, n2, n3, n4;
+
+  /* initialize list for breadth first processing of vectors */
+  list[0] = pixels;
+
+  /* recursively process vector */
+  for (i=0, m=1, n=1, level=5; i < n; i++) {
+    for (; level > 0; i++) {
+
+      /* process next depth */
+      if (i == m) {
+	m = n;
+
+	if (--level == 0)
+	  break;
+      }
+
+      /* divide block if next bit set */
+      if (get_bits (bitbuf, 1) == 0)
+	break;
+
+      /* add child nodes */
+      list[n++] = list[i];
+      list[n++] = list[i] + (((level & 1) ? pitch : 1) << ((level / 2) + 1));
+    }
+
+    /* destination address and vector size */
+    dst = (uint32_t *) list[i];
+    width = 1 << ((4 + level) /2);
+    height = 1 << ((3 + level) /2);
+
+    /* get number of stages (-1 skips vector, 0 for mean only) */
+    bit_cache = get_bit_cache (bitbuf);
+
+    if (intra)
+      vlc = &intra_vector_tables[level][bit_cache >> (32 - 7)];
+    else
+      vlc = &inter_vector_tables[level][bit_cache >> (32 - 6)];
+
+    /* flush bits */
+    stages	    = vlc->value;
+    bitbuf->bitpos += vlc->length;
+
+    if (stages == -1) {
+      if (intra) {
+	for (y=0; y < height; y++) {
+	  memset (&dst[y*(pitch / 4)], 0, width);
+	}
+      }
+      continue;		/* skip vector */
+    }
+
+    if ((stages > 0) && (level >= 4)) {
+      return -1;	/* invalid vector */
+    }
+
+    /* get mean value for vector */
+    bit_cache = get_bit_cache (bitbuf);
+
+    if (intra) {
+      if (bit_cache >= 0x25000000)
+	vlc = &intra_mean_table_0[(bit_cache >> (32 - 8)) - 37];
+      else if (bit_cache >= 0x03400000)
+	vlc = &intra_mean_table_1[(bit_cache >> (32 - 10)) - 13];
+      else if (bit_cache >= 0x00040000) 
+	vlc = &intra_mean_table_2[(bit_cache >> (32 - 14)) - 1];
+      else
+	vlc = &intra_mean_table_3[bit_cache >> (32 - 20)];
+    } else {
+      if (bit_cache >= 0x0B000000)
+	vlc = &inter_mean_table_0[(bit_cache >> (32 - 8)) - 11];
+      else if (bit_cache >= 0x01200000)
+	vlc = &inter_mean_table_1[(bit_cache >> (32 - 12)) - 18];
+      else if (bit_cache >= 0x002E0000) 
+	vlc = &inter_mean_table_2[(bit_cache >> (32 - 15)) - 23];
+      else if (bit_cache >= 0x00094000)
+	vlc = &inter_mean_table_3[(bit_cache >> (32 - 18)) - 37];
+      else if (bit_cache >= 0x00049000)
+	vlc = &inter_mean_table_4[(bit_cache >> (32 - 20)) - 73];
+      else
+	vlc = &inter_mean_table_5[bit_cache >> (32 - 22)];
+    }
+
+    /* flush bits */
+    mean	    = vlc->value;
+    bitbuf->bitpos += vlc->length;
+
+    if (intra && stages == 0) {
+      for (y=0; y < height; y++) {
+	memset (&dst[y*(pitch / 4)], mean, width);
+      }
+    } else {
+      codebook = (uint32_t *) (intra ? intra_codebooks[level] : inter_codebooks[level]);
+      bit_cache = get_bits (bitbuf, 4*stages);
+
+      /* calculate codebook entries for this vector */
+      for (j=0; j < stages; j++) {
+	entries[j] = (((bit_cache >> (4*(stages - j - 1))) & 0xF) + 16*j) << (level + 1);
+      }
+
+      mean -= (stages * 128);
+      n4    = ((mean + (mean >> 31)) << 16) | (mean & 0xFFFF);
+
+      for (y=0; y < height; y++) {
+	for (x=0; x < (width / 4); x++, codebook++) {
+	  if (intra) {
+	    n1 = n4;
+	    n2 = n4;
+	  } else {
+	    n3 = dst[x];
+
+	    /* add mean value to vector */
+	    n1 = ((n3 & 0xFF00FF00) >> 8) + n4;
+	    n2 =  (n3 & 0x00FF00FF)	  + n4;
+	  }
+
+	  /* add codebook entries to vector */
+	  for (j=0; j < stages; j++) {
+	    n3  = codebook[entries[j]] ^ 0x80808080;
+	    n1 += ((n3 & 0xFF00FF00) >> 8);
+	    n2 +=  (n3 & 0x00FF00FF);
+	  }
+
+	  /* clip to [0..255] */
+	  if (n1 & 0xFF00FF00) {
+	    n3  = ((( n1 >> 15) & 0x00010001) | 0x01000100) - 0x00010001;
+	    n1 += 0x7F007F00;
+	    n1 |= (((~n1 >> 15) & 0x00010001) | 0x01000100) - 0x00010001;
+	    n1 &= (n3 & 0x00FF00FF);
+	  }
+
+	  if (n2 & 0xFF00FF00) {
+	    n3  = ((( n2 >> 15) & 0x00010001) | 0x01000100) - 0x00010001;
+	    n2 += 0x7F007F00;
+	    n2 |= (((~n2 >> 15) & 0x00010001) | 0x01000100) - 0x00010001;
+	    n2 &= (n3 & 0x00FF00FF);
+	  }
+
+	  /* store result */
+	  dst[x] = (n1 << 8) | n2;
+        }
+
+        dst += (pitch / 4);
+      }
+    }
+  }
+
+  return 0;
+}
+
+static int decode_motion_vector (bit_buffer_t *bitbuf, svq1_pmv_t *mv, svq1_pmv_t **pmv) {
+  uint32_t    bit_cache;
+  vlc_code_t *vlc;
+  int	      diff, sign;
+  int	      i;
+
+  for (i=0; i < 2; i++) {
+
+    /* get motion code */
+    bit_cache = get_bit_cache (bitbuf);
+
+    if (!(bit_cache & 0xFFE00000))
+      return -1;	/* invalid vlc code */
+
+    if (bit_cache & 0x80000000) {
+      diff = 0;
+
+      /* flush bit */
+      bitbuf->bitpos++;
+
+    } else {
+      if (bit_cache >= 0x06000000) {
+        vlc = &motion_table_0[(bit_cache >> (32 - 7)) - 3];
+      } else {
+        vlc = &motion_table_1[(bit_cache >> (32 - 12)) - 2];
+      }
+
+      /* decode motion vector differential */
+      sign = (int) (bit_cache << (vlc->length - 1)) >> 31;
+      diff = (vlc->value ^ sign) - sign;
+
+      /* flush bits */
+      bitbuf->bitpos += vlc->length;
+    }
+
+    /* add median of motion vector predictors and clip result */
+    if (i == 1)
+      mv->y = ((diff + MEDIAN(pmv[0]->y, pmv[1]->y, pmv[2]->y)) << 26) >> 26;
+    else
+      mv->x = ((diff + MEDIAN(pmv[0]->x, pmv[1]->x, pmv[2]->x)) << 26) >> 26;
+  }
+
+  return 0;
+}
+
+static void skip_block (uint8_t *current, uint8_t *previous, int pitch, int x, int y) {
+  uint8_t *src;
+  uint8_t *dst;
+  int	   i;
+
+  src = &previous[x + y*pitch];
+  dst = current;
+
+  for (i=0; i < 16; i++) {
+    memcpy (dst, src, 16);
+    src += pitch;
+    dst += pitch;
+  }
+}
+
+static int motion_inter_block (bit_buffer_t *bitbuf,
+			       uint8_t *current, uint8_t *previous, int pitch,
+			       svq1_pmv_t *motion, int x, int y) {
+  uint8_t    *src;
+  uint8_t    *dst;
+  svq1_pmv_t  mv;
+  svq1_pmv_t *pmv[3];
+  int	      sx, sy;
+  int	      result;
+
+  /* predict and decode motion vector */
+  pmv[0] = &motion[0];
+  pmv[1] = &motion[(x / 8) + 2];
+  pmv[2] = &motion[(x / 8) + 4];
+
+  if (y == 0) {
+    pmv[1] = pmv[0];
+    pmv[2] = pmv[0];
+  }
+
+  result = decode_motion_vector (bitbuf, &mv, pmv);
+
+  if (result != 0)
+    return result;
+
+  motion[0].x		= mv.x;
+  motion[0].y		= mv.y;
+  motion[(x / 8) + 2].x	= mv.x;
+  motion[(x / 8) + 2].y	= mv.y;
+  motion[(x / 8) + 3].x	= mv.x;
+  motion[(x / 8) + 3].y	= mv.y;
+
+  src = &previous[(x + (mv.x >> 1)) + (y + (mv.y >> 1))*pitch];
+  dst = current;
+
+  /* form prediction */
+  if (mv.y & 0x1) {
+    if (mv.x & 0x1) {
+      for (sy=0; sy < 16; sy++) {
+	for (sx=0; sx < 16; sx++) {
+	  dst[sx] = (src[sx] + src[sx + 1] + src[sx + pitch] + src[sx + pitch + 1] + 2) >> 2;
+	}
+	src += pitch;
+	dst += pitch;
+      }
+    } else {
+      for (sy=0; sy < 16; sy++) {
+	for (sx=0; sx < 16; sx++) {
+	  dst[sx] = (src[sx] + src[sx + pitch] + 1) >> 1;
+	}
+	src += pitch;
+	dst += pitch;
+      }
+    }
+  } else {
+    if (mv.x & 0x1) {
+      for (sy=0; sy < 16; sy++) {
+	for (sx=0; sx < 16; sx++) {
+	  dst[sx] = (src[sx] + src[sx + 1] + 1) >> 1;
+	}
+	src += pitch;
+	dst += pitch;
+      }
+    } else {
+      for (sy=0; sy < 16; sy++) {
+	memcpy (dst, src, 16);
+	src += pitch;
+	dst += pitch;
+      }
+    }
+  }
+
+  return 0;
+}
+
+static int motion_inter_4v_block (bit_buffer_t *bitbuf,
+				  uint8_t *current, uint8_t *previous, int pitch,
+				  svq1_pmv_t *motion,int x, int y) {
+  uint8_t    *src;
+  uint8_t    *dst;
+  svq1_pmv_t  mv;
+  svq1_pmv_t *pmv[4];
+  int	      sx, sy;
+  int	      i, result;
+
+  /* predict and decode motion vector (0) */
+  pmv[0] = &motion[0];
+  pmv[1] = &motion[(x / 8) + 2];
+  pmv[2] = &motion[(x / 8) + 4];
+
+  if (y == 0) {
+    pmv[1] = pmv[0];
+    pmv[2] = pmv[0];
+  }
+
+  result = decode_motion_vector (bitbuf, &mv, pmv);
+
+  if (result != 0)
+    return result;
+
+  /* predict and decode motion vector (1) */
+  pmv[0] = &mv;
+  pmv[1] = &motion[(x / 8) + 3];
+
+  if (y == 0) {
+    pmv[1] = pmv[0];
+    pmv[2] = pmv[0];
+  }
+
+  result = decode_motion_vector (bitbuf, &motion[0], pmv);
+
+  if (result != 0)
+    return result;
+
+  /* predict and decode motion vector (2) */
+  pmv[1] = &motion[0];
+  pmv[2] = &motion[(x / 8) + 1];
+
+  result = decode_motion_vector (bitbuf, &motion[(x / 8) + 2], pmv);
+
+  if (result != 0)
+    return result;
+
+  /* predict and decode motion vector (3) */
+  pmv[2] = &motion[(x / 8) + 2];
+  pmv[3] = &motion[(x / 8) + 3];
+
+  result = decode_motion_vector (bitbuf, pmv[3], pmv);
+
+  if (result != 0)
+    return result;
+
+  /* form predictions */
+  for (i=0; i < 4; i++) {
+    src = &previous[(x + (pmv[i]->x >> 1)) + (y + (pmv[i]->y >> 1))*pitch];
+    dst = current;
+
+    if (pmv[i]->y & 0x1) {
+      if (pmv[i]->x & 0x1) {
+	for (sy=0; sy < 8; sy++) {
+	  for (sx=0; sx < 8; sx++) { 
+	    dst[sx] = (src[sx] + src[sx + 1] + src[sx + pitch] + src[sx + pitch + 1] + 2) >> 2;
+	  }
+	  src += pitch;
+	  dst += pitch;
+	}
+      } else {
+	for (sy=0; sy < 8; sy++) {
+	  for (sx=0; sx < 8; sx++) {
+	    dst[sx] = (src[sx] + src[sx + pitch] + 1) >> 1;
+	  }
+	  src += pitch;
+	  dst += pitch;
+	}
+      }
+    } else {
+      if (pmv[i]->x & 0x1) {
+	for (sy=0; sy < 8; sy++) {
+	  for (sx=0; sx < 8; sx++) {
+	    dst[sx] = (src[sx] + src[sx + 1] + 1) >> 1;
+	  }
+	  src += pitch;
+	  dst += pitch;
+	}
+      } else {
+	for (sy=0; sy < 8; sy++) {
+	  memcpy (dst, src, 8);
+	  src += pitch;
+	  dst += pitch;
+	}
+      }
+    }
+
+    /* select next block */
+    if (i & 1) {
+      current  += 8*(pitch - 1);
+      previous += 8*(pitch - 1);
+    } else {
+      current  += 8;
+      previous += 8;
+    }
+  }
+
+  return 0;
+}
+
+static int decode_delta_block (bit_buffer_t *bitbuf,
+			uint8_t *current, uint8_t *previous, int pitch,
+			svq1_pmv_t *motion, int x, int y) {
+  uint32_t bit_cache;
+  uint32_t block_type;
+  int	   result = 0;
+
+  /* get block type */
+  bit_cache = get_bit_cache (bitbuf);
+
+  bit_cache	>>= (32 - 3);
+  block_type	  = block_type_table[bit_cache].value;
+  bitbuf->bitpos += block_type_table[bit_cache].length;
+
+  /* reset motion vectors */
+  if (block_type == SVQ1_BLOCK_SKIP || block_type == SVQ1_BLOCK_INTRA) {
+    motion[0].x		  = 0;
+    motion[0].y		  = 0;
+    motion[(x / 8) + 2].x = 0;
+    motion[(x / 8) + 2].y = 0;
+    motion[(x / 8) + 3].x = 0;
+    motion[(x / 8) + 3].y = 0;
+  }
+
+  switch (block_type) {
+  case SVQ1_BLOCK_SKIP:
+    skip_block (current, previous, pitch, x, y);
+    break;
+
+  case SVQ1_BLOCK_INTER:
+    result = motion_inter_block (bitbuf, current, previous, pitch, motion, x, y);
+
+    if (result != 0)
+      break;
+
+    result = decode_svq1_block (bitbuf, current, pitch, 0);
+    break;
+
+  case SVQ1_BLOCK_INTER_4V:
+    result = motion_inter_4v_block (bitbuf, current, previous, pitch, motion, x, y);
+
+    if (result != 0)
+      break;
+
+    result = decode_svq1_block (bitbuf, current, pitch, 0);
+    break;
+
+  case SVQ1_BLOCK_INTRA:
+    result = decode_svq1_block (bitbuf, current, pitch, 1);
+    break;
+  }
+
+  return result;
+}
+
+static int decode_frame_header (bit_buffer_t *bitbuf, svq1_t *svq1) {
+  int frame_size_code;
+
+  /* unknown field */
+  get_bits (bitbuf, 8);
+
+  /* frame type */
+  svq1->frame_type = get_bits (bitbuf, 2);
+
+  if (svq1->frame_type == 3)
+    return -1;
+
+  if (svq1->frame_type == SVQ1_FRAME_INTRA) {
+
+    /* unknown fields */
+    if (svq1->frame_code == 0x50 || svq1->frame_code == 0x60) {
+      get_bits (bitbuf, 16);
+    }
+
+    if ((svq1->frame_code ^ 0x10) >= 0x50) {
+      bitbuf->bitpos += 8*get_bits (bitbuf, 8);
+    }
+
+    get_bits (bitbuf, 2);
+    get_bits (bitbuf, 2);
+    get_bits (bitbuf, 1);
+
+    /* load frame size */
+    frame_size_code = get_bits (bitbuf, 3);
+
+    if (frame_size_code == 7) {
+      /* load width, height (12 bits each) */
+      svq1->frame_width = get_bits (bitbuf, 12);
+      svq1->frame_height = get_bits (bitbuf, 12);
+
+      if (!svq1->frame_width || !svq1->frame_height)
+        return -1;
+    } else {
+      /* get width, height from table */
+      svq1->frame_width = frame_size_table[frame_size_code].width;
+      svq1->frame_height = frame_size_table[frame_size_code].height;
+    }
+  }
+
+  /* unknown fields */
+  if (get_bits (bitbuf, 1) == 1) {
+    get_bits (bitbuf, 1);
+    get_bits (bitbuf, 1);
+
+    if (get_bits (bitbuf, 2) != 0)
+      return -1;
+  }
+
+  if (get_bits (bitbuf, 1) == 1) {
+    get_bits (bitbuf, 1);
+    get_bits (bitbuf, 4);
+    get_bits (bitbuf, 1);
+    get_bits (bitbuf, 2);
+
+    while (get_bits (bitbuf, 1) == 1) {
+      get_bits (bitbuf, 8);
+    }
+  }
+  
+  return 0;
+}
+
+int svq1_decode_frame (svq1_t *svq1, uint8_t *buffer) {
+  bit_buffer_t	bitbuf;
+  uint8_t      *current, *previous;
+  int		result, i, x, y, width, height;
+  int		luma_size, chroma_size;
+
+  /* initialize bit buffer */
+  bitbuf.buffer	= buffer;
+  bitbuf.bitpos	= 0;
+
+  /* decode frame header */
+  svq1->frame_code = get_bits (&bitbuf, 22);
+
+  if ((svq1->frame_code & ~0x70) || !(svq1->frame_code & 0x60))
+    return -1;
+
+  /* swap some header bytes (why?) */
+  if (svq1->frame_code != 0x20) {
+    uint32_t *src = (uint32_t *) (buffer + 4);
+
+    for (i=0; i < 4; i++) {
+      src[i] = ((src[i] << 16) | (src[i] >> 16)) ^ src[7 - i];
+    }
+  }
+
+  result = decode_frame_header (&bitbuf, svq1);
+
+  if (result != 0)
+    return result;
+
+  /* check frame size (changed?) */
+  if (((svq1->frame_width + 3) & ~0x3) != svq1->width ||
+      ((svq1->frame_height + 3) & ~0x3) != svq1->height) {
+
+    /* free current buffers */
+    free (svq1->current);
+    free (svq1->previous);
+    free (svq1->motion);
+
+    svq1->width		= (svq1->frame_width + 3) & ~0x3;
+    svq1->height	= (svq1->frame_height + 3) & ~0x3;
+    svq1->luma_width	= (svq1->width + 15) & ~0xF;
+    svq1->luma_height	= (svq1->height + 15) & ~0xF;
+    svq1->chroma_width	= ((svq1->width / 4) + 15) & ~0xF;
+    svq1->chroma_height	= ((svq1->height / 4) + 15) & ~0xF;
+
+    /* allocate new pixel and motion buffers for updated frame size */
+    luma_size		= svq1->luma_width * svq1->luma_height;
+    chroma_size		= svq1->chroma_width * svq1->chroma_height;
+
+    svq1->motion	= (svq1_pmv_t *) malloc (((svq1->luma_width / 8) + 3) * sizeof(svq1_pmv_t));
+    svq1->current	= (uint8_t *) malloc (luma_size + 2*chroma_size);
+    svq1->previous	= (uint8_t *) malloc (luma_size + 2*chroma_size);
+    svq1->offsets[0]	= 0;
+    svq1->offsets[1]	= luma_size;
+    svq1->offsets[2]	= luma_size + chroma_size;
+
+    for (i=0; i < 3; i++) {
+      svq1->base[i] = svq1->current + svq1->offsets[i];
+    }
+
+    svq1->reference_frame = 0;
+  }
+
+  /* delta frame requires reference frame */
+  if (svq1->frame_type != SVQ1_FRAME_INTRA && !svq1->reference_frame)
+    return -1;
+
+  /* decode y, u and v components */
+  for (i=0; i < 3; i++) {
+    if (i == 0) {
+      width  = svq1->luma_width;
+      height = svq1->luma_height;
+    } else {
+      width  = svq1->chroma_width;
+      height = svq1->chroma_height;
+    }
+
+    current  = svq1->current + svq1->offsets[i];
+    previous = svq1->previous + svq1->offsets[i];
+
+    if (svq1->frame_type == SVQ1_FRAME_INTRA) {
+      /* keyframe */
+      for (y=0; y < height; y+=16) {
+	for (x=0; x < width; x+=16) {
+	  result = decode_svq1_block (&bitbuf, &current[x], width, 1);
+
+	  if (result != 0)
+	    return result;
+	}
+
+	current += 16*width;
+      }
+    } else {
+      /* delta frame */
+      memset (svq1->motion, 0, ((width / 8) + 3) * sizeof(svq1_pmv_t));
+
+      for (y=0; y < height; y+=16) {
+	for (x=0; x < width; x+=16) {
+	  result = decode_delta_block (&bitbuf, &current[x], previous,
+				       width, svq1->motion, x, y);
+
+	  if (result != 0)
+	    return result;
+	}
+
+	svq1->motion[0].x = 0;
+	svq1->motion[0].y = 0;
+
+	current += 16*width;
+      }
+    }
+  }
+
+  /* update pixel buffers for frame copy */
+  for (i=0; i < 3; i++) {
+    svq1->base[i] = svq1->current + svq1->offsets[i];
+  }
+
+  /* update backward reference frame */
+  if (svq1->frame_type != SVQ1_FRAME_DROPPABLE) {
+    uint8_t *tmp = svq1->previous;
+    svq1->previous = svq1->current;
+    svq1->current = tmp;
+    svq1->reference_frame = 1;    
+  }
+
+  return 0;
+}
+
+void svq1_free (svq1_t *svq1){
+  if (svq1) {
+    free (svq1->current);
+    free (svq1->previous);
+    free (svq1->motion);
+    free (svq1);
+  }
+}
+