FFmpeg
rle.c
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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 "libavutil/common.h"
23 
24 #include "avcodec.h"
25 #include "rle.h"
26 
27 int ff_rle_count_pixels(const uint8_t *start, int len, int bpp, int same)
28 {
29  const uint8_t *pos;
30  int count = 1;
31 
32  for (pos = start + bpp; count < FFMIN(127, len); pos += bpp, count++) {
33  if (same != !memcmp(pos - bpp, pos, bpp)) {
34  if (!same) {
35  /* if bpp == 1, then 0 1 1 0 is more efficiently encoded as a
36  * single raw block of pixels. For larger bpp, RLE is as good
37  * or better */
38  if (bpp == 1 && count + 1 < FFMIN(127, len) && *pos != *(pos + 1))
39  continue;
40 
41  /* if RLE can encode the next block better than as a raw block,
42  * back up and leave _all_ the identical pixels for RLE */
43  count--;
44  }
45  break;
46  }
47  }
48 
49  return count;
50 }
51 
52 int ff_rle_encode(uint8_t *outbuf, int out_size, const uint8_t *ptr, int bpp,
53  int w, int add_rep, int xor_rep, int add_raw, int xor_raw)
54 {
55  int count, x;
56  uint8_t *out = outbuf;
57 
58  for (x = 0; x < w; x += count) {
59  /* see if we can encode the next set of pixels with RLE */
60  if ((count = ff_rle_count_pixels(ptr, w - x, bpp, 1)) > 1) {
61  if (out + bpp + 1 > outbuf + out_size)
62  return -1;
63 
64  *out++ = (count ^ xor_rep) + add_rep;
65  memcpy(out, ptr, bpp);
66  out += bpp;
67  } else {
68  /* fall back on uncompressed */
69  count = ff_rle_count_pixels(ptr, w - x, bpp, 0);
70  if (out + bpp * count >= outbuf + out_size)
71  return -1;
72 
73  *out++ = (count ^ xor_raw) + add_raw;
74  memcpy(out, ptr, bpp * count);
75  out += bpp * count;
76  }
77 
78  ptr += count * bpp;
79  }
80 
81  return out - outbuf;
82 }
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:27
int out_size
Definition: movenc.c:55
uint8_t
unsigned int pos
Definition: spdifenc.c:410
GLsizei count
Definition: opengl_enc.c:108
#define FFMIN(a, b)
Definition: common.h:96
uint8_t w
Definition: llviddspenc.c:38
Libavcodec external API header.
common internal and external API header
int len
FILE * out
Definition: movenc.c:54
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:52