FFmpeg
xsubdec.c
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1 /*
2  * XSUB subtitle decoder
3  * Copyright (c) 2007 Reimar Döffinger
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/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, ret;
57  int64_t packet_time = 0;
58  GetBitContext gb;
59  int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
60 
61  // check that at least header fits
62  if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
63  av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
64  return -1;
65  }
66 
67  // read start and end time
68  if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
69  av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
70  return -1;
71  }
72  if (avpkt->pts != AV_NOPTS_VALUE)
73  packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
74  sub->start_display_time = parse_timecode(buf + 1, packet_time);
75  sub->end_display_time = parse_timecode(buf + 14, packet_time);
76  buf += 27;
77 
78  // read header
79  w = bytestream_get_le16(&buf);
80  h = bytestream_get_le16(&buf);
81  if (av_image_check_size(w, h, 0, avctx) < 0)
82  return -1;
83  x = bytestream_get_le16(&buf);
84  y = bytestream_get_le16(&buf);
85  // skip bottom right position, it gives no new information
86  bytestream_get_le16(&buf);
87  bytestream_get_le16(&buf);
88  // The following value is supposed to indicate the start offset
89  // (relative to the palette) of the data for the second field,
90  // however there are files in which it has a bogus value and thus
91  // we just ignore it
92  bytestream_get_le16(&buf);
93 
94  if (buf_end - buf < h + 3*4)
95  return AVERROR_INVALIDDATA;
96 
97  // allocate sub and set values
98  sub->rects = av_mallocz(sizeof(*sub->rects));
99  if (!sub->rects)
100  return AVERROR(ENOMEM);
101 
102  sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
103  if (!sub->rects[0]) {
104  av_freep(&sub->rects);
105  return AVERROR(ENOMEM);
106  }
107  sub->rects[0]->x = x; sub->rects[0]->y = y;
108  sub->rects[0]->w = w; sub->rects[0]->h = h;
109  sub->rects[0]->type = SUBTITLE_BITMAP;
110  sub->rects[0]->linesize[0] = w;
111  sub->rects[0]->data[0] = av_malloc(w * h);
112  sub->rects[0]->nb_colors = 4;
113  sub->rects[0]->data[1] = av_mallocz(AVPALETTE_SIZE);
114  if (!sub->rects[0]->data[0] || !sub->rects[0]->data[1]) {
115  av_freep(&sub->rects[0]->data[1]);
116  av_freep(&sub->rects[0]->data[0]);
117  av_freep(&sub->rects[0]);
118  av_freep(&sub->rects);
119  return AVERROR(ENOMEM);
120  }
121  sub->num_rects = 1;
122 
123  // read palette
124  for (i = 0; i < sub->rects[0]->nb_colors; i++)
125  ((uint32_t*)sub->rects[0]->data[1])[i] = bytestream_get_be24(&buf);
126 
127  if (!has_alpha) {
128  // make all except background (first entry) non-transparent
129  for (i = 1; i < sub->rects[0]->nb_colors; i++)
130  ((uint32_t *)sub->rects[0]->data[1])[i] |= 0xff000000;
131  } else {
132  for (i = 0; i < sub->rects[0]->nb_colors; i++)
133  ((uint32_t *)sub->rects[0]->data[1])[i] |= *buf++ << 24;
134  }
135 
136 #if FF_API_AVPICTURE
138 {
140  int j;
141  rect = sub->rects[0];
142  for (j = 0; j < 4; j++) {
143  rect->pict.data[j] = rect->data[j];
144  rect->pict.linesize[j] = rect->linesize[j];
145  }
146 }
148 #endif
149 
150  // process RLE-compressed data
151  if ((ret = init_get_bits8(&gb, buf, buf_end - buf)) < 0)
152  return ret;
153  bitmap = sub->rects[0]->data[0];
154  for (y = 0; y < h; y++) {
155  // interlaced: do odd lines
156  if (y == (h + 1) / 2) bitmap = sub->rects[0]->data[0] + w;
157  for (x = 0; x < w; ) {
158  int log2 = ff_log2_tab[show_bits(&gb, 8)];
159  int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
160  int color = get_bits(&gb, 2);
161  run = FFMIN(run, w - x);
162  // run length 0 means till end of row
163  if (!run) run = w - x;
164  memset(bitmap, color, run);
165  bitmap += run;
166  x += run;
167  }
168  // interlaced, skip every second line
169  bitmap += w;
170  align_get_bits(&gb);
171  }
172  *data_size = 1;
173  return buf_size;
174 }
175 
177  .name = "xsub",
178  .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
179  .type = AVMEDIA_TYPE_SUBTITLE,
180  .id = AV_CODEC_ID_XSUB,
181  .init = decode_init,
182  .decode = decode_frame,
183 };
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
int x
top left corner of pict, undefined when pict is not set
Definition: avcodec.h:3910
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:100
misc image utilities
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:379
int nb_colors
number of colors in pict, undefined when pict is not set
Definition: avcodec.h:3914
int size
Definition: avcodec.h:1481
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:1778
unsigned num_rects
Definition: avcodec.h:3948
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:236
uint8_t run
Definition: svq3.c:206
AVCodec.
Definition: avcodec.h:3492
attribute_deprecated AVPicture pict
Definition: avcodec.h:3921
#define log2(x)
Definition: libm.h:404
AVSubtitleRect ** rects
Definition: avcodec.h:3949
int w
width of pict, undefined when pict is not set
Definition: avcodec.h:3912
uint8_t
#define av_cold
Definition: attributes.h:82
#define av_malloc(s)
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:77
#define AVPALETTE_SIZE
Definition: pixfmt.h:32
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
attribute_deprecated int linesize[AV_NUM_DATA_POINTERS]
number of bytes per line
Definition: avcodec.h:3881
static const uint8_t tc_muls[9]
Definition: xsubdec.c:34
uint8_t * data
Definition: avcodec.h:1480
bitstream reader API header.
int h
height of pict, undefined when pict is not set
Definition: avcodec.h:3913
#define av_log(a,...)
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:142
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
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:3911
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
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
const char * name
Name of the codec implementation.
Definition: avcodec.h:3499
static const uint8_t tc_offsets[9]
Definition: xsubdec.c:33
uint32_t end_display_time
Definition: avcodec.h:3947
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:282
A bitmap, pict will be set.
Definition: avcodec.h:3892
int linesize[4]
Definition: avcodec.h:3928
#define FFMIN(a, b)
Definition: common.h:96
uint8_t w
Definition: llviddspenc.c:38
static unsigned int show_bits(GetBitContext *s, int n)
Show 1-25 bits.
Definition: get_bits.h:446
attribute_deprecated uint8_t * data[AV_NUM_DATA_POINTERS]
pointers to the image data planes
Definition: avcodec.h:3879
uint8_t * data[4]
data+linesize for the bitmap of this subtitle.
Definition: avcodec.h:3927
const uint8_t ff_log2_tab[256]
Definition: log2_tab.c:23
Libavcodec external API header.
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition: avutil.h:260
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:677
main external API structure.
Definition: avcodec.h:1568
AVCodec ff_xsub_decoder
Definition: xsubdec.c:176
unsigned int codec_tag
fourcc (LSB first, so "ABCD" -> (&#39;D&#39;<<24) + (&#39;C&#39;<<16) + (&#39;B&#39;<<8) + &#39;A&#39;).
Definition: avcodec.h:1593
void * buf
Definition: avisynth_c.h:766
Definition: f_ebur128.c:91
Rational number (pair of numerator and denominator).
Definition: rational.h:58
#define FF_DISABLE_DEPRECATION_WARNINGS
Definition: internal.h:84
uint32_t start_display_time
Definition: avcodec.h:3946
#define FF_ENABLE_DEPRECATION_WARNINGS
Definition: internal.h:85
static const uint8_t * align_get_bits(GetBitContext *s)
Definition: get_bits.h:693
#define av_freep(p)
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
enum AVSubtitleType type
Definition: avcodec.h:3930
#define MKTAG(a, b, c, d)
Definition: common.h:366
This structure stores compressed data.
Definition: avcodec.h:1457
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1473
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248