FFmpeg
rle.c
Go to the documentation of this file.
1 /*
2  * RLE encoder
3  * Copyright (c) 2007 Bobby Bingham
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include <string.h>
23 
24 #include "libavutil/common.h"
25 
26 #include "rle.h"
27 
28 int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
29 {
30  const uint8_t *pos;
31  int count = 1;
32 
33  for (pos = start + bpp; count < FFMIN(127, len); pos += bpp, count++) {
34  if (same != !memcmp(pos - bpp, pos, bpp)) {
35  if (!same) {
36  /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a
37  * single raw block of pixels. For larger bpp, RLE is as good
38  * or better */
39  if (bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos + 1))
40  continue;
41 
42  /* if RLE can encode the next block better than as a raw block,
43  * back up and leave _all_ the identical pixels for RLE */
44  count--;
45  }
46  break;
47  }
48  }
49 
50  return count;
51 }
52 
53 int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp,
54  int w, int add_rep, int xor_rep, int add_raw, int xor_raw)
55 {
56  int count, x;
57  uint8_t *out = outbuf;
58 
59  for (x = 0; x < w; x += count) {
60  /* see if we can encode the next set of pixels with RLE */
61  if ((count = ff_rle_count_pixels(ptr, w - x, bpp, 1)) > 1) {
62  if (out + bpp + 1 > outbuf + out_size)
63  return -1;
64 
65  *out++ = (count ^ xor_rep) + add_rep;
66  memcpy(out, ptr, bpp);
67  out += bpp;
68  } else {
69  /* fall back on uncompressed */
70  count = ff_rle_count_pixels(ptr, w - x, bpp, 0);
71  if (out + bpp * count >= outbuf + out_size)
72  return -1;
73 
74  *out++ = (count ^ xor_raw) + add_raw;
75  memcpy(out, ptr, bpp * count);
76  out += bpp * count;
77  }
78 
79  ptr += count * bpp;
80  }
81 
82  return out - outbuf;
83 }
rle.h
out
FILE * out
Definition: movenc.c:54
out_size
int out_size
Definition: movenc.c:55
w
uint8_t w
Definition: llviddspenc.c:38
common.h
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
ff_rle_count_pixels
int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
Count up to 127 consecutive pixels which are either all the same or all differ from the previous and ...
Definition: rle.c:28
len
int len
Definition: vorbis_enc_data.h:426
ff_rle_encode
int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp, int w, int add_rep, int xor_rep, int add_raw, int xor_raw)
RLE compress the row, with maximum size of out_size.
Definition: rle.c:53
pos
unsigned int pos
Definition: spdifenc.c:412