Libav
xsubdec.c
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1 /*
2  * XSUB subtitle decoder
3  * Copyright (c) 2007 Reimar Döffinger
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; 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/mathematics.h"
23 #include "libavutil/imgutils.h"
24 #include "avcodec.h"
25 #include "get_bits.h"
26 #include "bytestream.h"
27 
28 static av_cold int decode_init(AVCodecContext *avctx) {
29  avctx->pix_fmt = AV_PIX_FMT_PAL8;
30  return 0;
31 }
32 
33 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
34 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
35 
36 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
37  int i;
38  int64_t ms = 0;
39  if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
40  return AV_NOPTS_VALUE;
41  for (i = 0; i < sizeof(tc_offsets); i++) {
42  uint8_t c = buf[tc_offsets[i]] - '0';
43  if (c > 9) return AV_NOPTS_VALUE;
44  ms = (ms + c) * tc_muls[i];
45  }
46  return ms - packet_time;
47 }
48 
49 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
50  AVPacket *avpkt) {
51  const uint8_t *buf = avpkt->data;
52  int buf_size = avpkt->size;
53  AVSubtitle *sub = data;
54  const uint8_t *buf_end = buf + buf_size;
55  uint8_t *bitmap;
56  int w, h, x, y, i;
57  int64_t packet_time = 0;
58  GetBitContext gb;
59 
60  memset(sub, 0, sizeof(*sub));
61 
62  // check that at least header fits
63  if (buf_size < 27 + 7 * 2 + 4 * 3) {
64  av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
65  return -1;
66  }
67 
68  // read start and end time
69  if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
70  av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
71  return -1;
72  }
73  if (avpkt->pts != AV_NOPTS_VALUE)
74  packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
75  sub->start_display_time = parse_timecode(buf + 1, packet_time);
76  sub->end_display_time = parse_timecode(buf + 14, packet_time);
77  buf += 27;
78 
79  // read header
80  w = bytestream_get_le16(&buf);
81  h = bytestream_get_le16(&buf);
82  if (av_image_check_size(w, h, 0, avctx) < 0)
83  return -1;
84  x = bytestream_get_le16(&buf);
85  y = bytestream_get_le16(&buf);
86  // skip bottom right position, it gives no new information
87  bytestream_get_le16(&buf);
88  bytestream_get_le16(&buf);
89  // The following value is supposed to indicate the start offset
90  // (relative to the palette) of the data for the second field,
91  // however there are files in which it has a bogus value and thus
92  // we just ignore it
93  bytestream_get_le16(&buf);
94 
95  // allocate sub and set values
96  sub->rects = av_mallocz(sizeof(*sub->rects));
97  sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
98  sub->num_rects = 1;
99  sub->rects[0]->x = x; sub->rects[0]->y = y;
100  sub->rects[0]->w = w; sub->rects[0]->h = h;
101  sub->rects[0]->type = SUBTITLE_BITMAP;
102  sub->rects[0]->pict.linesize[0] = w;
103  sub->rects[0]->pict.data[0] = av_malloc(w * h);
104  sub->rects[0]->nb_colors = 4;
105  sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
106 
107  // read palette
108  for (i = 0; i < sub->rects[0]->nb_colors; i++)
109  ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
110  // make all except background (first entry) non-transparent
111  for (i = 1; i < sub->rects[0]->nb_colors; i++)
112  ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
113 
114  // process RLE-compressed data
115  init_get_bits(&gb, buf, (buf_end - buf) * 8);
116  bitmap = sub->rects[0]->pict.data[0];
117  for (y = 0; y < h; y++) {
118  // interlaced: do odd lines
119  if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
120  for (x = 0; x < w; ) {
121  int log2 = ff_log2_tab[show_bits(&gb, 8)];
122  int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
123  int color = get_bits(&gb, 2);
124  run = FFMIN(run, w - x);
125  // run length 0 means till end of row
126  if (!run) run = w - x;
127  memset(bitmap, color, run);
128  bitmap += run;
129  x += run;
130  }
131  // interlaced, skip every second line
132  bitmap += w;
133  align_get_bits(&gb);
134  }
135  *data_size = 1;
136  return buf_size;
137 }
138 
140  .name = "xsub",
141  .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
142  .type = AVMEDIA_TYPE_SUBTITLE,
143  .id = AV_CODEC_ID_XSUB,
144  .init = decode_init,
145  .decode = decode_frame,
146 };
#define AVPALETTE_SIZE
Definition: avcodec.h:2959
void * av_malloc(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:62
int linesize[AV_NUM_DATA_POINTERS]
number of bytes per line
Definition: avcodec.h:2952
int x
top left corner of pict, undefined when pict is not set
Definition: avcodec.h:2983
misc image utilities
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:240
int nb_colors
number of colors in pict, undefined when pict is not set
Definition: avcodec.h:2987
int size
Definition: avcodec.h:974
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:1247
unsigned num_rects
Definition: avcodec.h:3011
uint8_t run
Definition: svq3.c:142
AVCodec.
Definition: avcodec.h:2755
#define log2(x)
Definition: libm.h:111
AVSubtitleRect ** rects
Definition: avcodec.h:3012
int w
width of pict, undefined when pict is not set
Definition: avcodec.h:2985
uint8_t
#define av_cold
Definition: attributes.h:66
8 bit with PIX_FMT_RGB32 palette
Definition: pixfmt.h:76
uint8_t * data[AV_NUM_DATA_POINTERS]
Definition: avcodec.h:2951
static const uint8_t tc_muls[9]
Definition: xsubdec.c:34
const char data[16]
Definition: mxf.c:66
uint8_t * data
Definition: avcodec.h:973
bitstream reader API header.
const uint8_t ff_log2_tab[256]
Definition: log2_tab.c:21
int h
height of pict, undefined when pict is not set
Definition: avcodec.h:2986
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:122
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:123
static av_cold int decode_init(AVCodecContext *avctx)
Definition: xsubdec.c:28
int y
top left corner of pict, undefined when pict is not set
Definition: avcodec.h:2984
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:142
static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
Definition: xsubdec.c:49
static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time)
Definition: xsubdec.c:36
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:148
const char * name
Name of the codec implementation.
Definition: avcodec.h:2762
static const uint8_t tc_offsets[9]
Definition: xsubdec.c:33
uint32_t end_display_time
Definition: avcodec.h:3010
int av_image_check_size(unsigned int w, unsigned int h, int log_offset, void *log_ctx)
Check if the given dimension of an image is valid, meaning that all bytes of the image can be address...
Definition: imgutils.c:220
A bitmap, pict will be set.
Definition: avcodec.h:2965
AVPicture pict
data+linesize for the bitmap of this subtitle.
Definition: avcodec.h:2993
#define FFMIN(a, b)
Definition: common.h:57
static unsigned int show_bits(GetBitContext *s, int n)
Show 1-25 bits.
Definition: get_bits.h:254
Libavcodec external API header.
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition: avutil.h:240
main external API structure.
Definition: avcodec.h:1054
AVCodec ff_xsub_decoder
Definition: xsubdec.c:139
rational number numerator/denominator
Definition: rational.h:43
static int init_get_bits(GetBitContext *s, const uint8_t *buffer, int bit_size)
Initialize GetBitContext.
Definition: get_bits.h:375
uint32_t start_display_time
Definition: avcodec.h:3009
static const uint8_t color[]
Definition: log.c:54
static const uint8_t * align_get_bits(GetBitContext *s)
Definition: get_bits.h:416
enum AVSubtitleType type
Definition: avcodec.h:2994
This structure stores compressed data.
Definition: avcodec.h:950
void * av_mallocz(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:205
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:966
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:228