FFmpeg
xsubdec.c
Go to the documentation of this file.
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 #include "internal.h"
28 
29 static av_cold int decode_init(AVCodecContext *avctx) {
30  avctx->pix_fmt = AV_PIX_FMT_PAL8;
31  return 0;
32 }
33 
34 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
35 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
36 
37 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
38  int i;
39  int64_t ms = 0;
40  if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
41  return AV_NOPTS_VALUE;
42  for (i = 0; i < sizeof(tc_offsets); i++) {
43  uint8_t c = buf[tc_offsets[i]] - '0';
44  if (c > 9) return AV_NOPTS_VALUE;
45  ms = (ms + c) * tc_muls[i];
46  }
47  return ms - packet_time;
48 }
49 
50 static int decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr,
51  AVPacket *avpkt) {
52  const uint8_t *buf = avpkt->data;
53  int buf_size = avpkt->size;
54  AVSubtitle *sub = data;
55  const uint8_t *buf_end = buf + buf_size;
56  uint8_t *bitmap;
57  int w, h, x, y, i, ret;
58  int64_t packet_time = 0;
59  GetBitContext gb;
60  int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
61 
62  // check that at least header fits
63  if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
64  av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
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  if (buf_end - buf < h + 3*4)
96  return AVERROR_INVALIDDATA;
97 
98  // allocate sub and set values
99  sub->rects = av_mallocz(sizeof(*sub->rects));
100  if (!sub->rects)
101  return AVERROR(ENOMEM);
102 
103  sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
104  if (!sub->rects[0]) {
105  av_freep(&sub->rects);
106  return AVERROR(ENOMEM);
107  }
108  sub->rects[0]->x = x; sub->rects[0]->y = y;
109  sub->rects[0]->w = w; sub->rects[0]->h = h;
110  sub->rects[0]->type = SUBTITLE_BITMAP;
111  sub->rects[0]->linesize[0] = w;
112  sub->rects[0]->data[0] = av_malloc(w * h);
113  sub->rects[0]->nb_colors = 4;
114  sub->rects[0]->data[1] = av_mallocz(AVPALETTE_SIZE);
115  if (!sub->rects[0]->data[0] || !sub->rects[0]->data[1]) {
116  av_freep(&sub->rects[0]->data[1]);
117  av_freep(&sub->rects[0]->data[0]);
118  av_freep(&sub->rects[0]);
119  av_freep(&sub->rects);
120  return AVERROR(ENOMEM);
121  }
122  sub->num_rects = 1;
123 
124  // read palette
125  for (i = 0; i < sub->rects[0]->nb_colors; i++)
126  ((uint32_t*)sub->rects[0]->data[1])[i] = bytestream_get_be24(&buf);
127 
128  if (!has_alpha) {
129  // make all except background (first entry) non-transparent
130  for (i = 1; i < sub->rects[0]->nb_colors; i++)
131  ((uint32_t *)sub->rects[0]->data[1])[i] |= 0xff000000;
132  } else {
133  for (i = 0; i < sub->rects[0]->nb_colors; i++)
134  ((uint32_t *)sub->rects[0]->data[1])[i] |= (unsigned)*buf++ << 24;
135  }
136 
137  // process RLE-compressed data
138  if ((ret = init_get_bits8(&gb, buf, buf_end - buf)) < 0)
139  return ret;
140  bitmap = sub->rects[0]->data[0];
141  for (y = 0; y < h; y++) {
142  // interlaced: do odd lines
143  if (y == (h + 1) / 2) bitmap = sub->rects[0]->data[0] + w;
144  for (x = 0; x < w; ) {
145  int log2 = ff_log2_tab[show_bits(&gb, 8)];
146  int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
147  int color = get_bits(&gb, 2);
148  run = FFMIN(run, w - x);
149  // run length 0 means till end of row
150  if (!run) run = w - x;
151  memset(bitmap, color, run);
152  bitmap += run;
153  x += run;
154  }
155  // interlaced, skip every second line
156  bitmap += w;
157  align_get_bits(&gb);
158  }
159  *got_sub_ptr = 1;
160  return buf_size;
161 }
162 
164  .name = "xsub",
165  .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
166  .type = AVMEDIA_TYPE_SUBTITLE,
167  .id = AV_CODEC_ID_XSUB,
168  .init = decode_init,
169  .decode = decode_frame,
170  .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
171 };
AVSubtitle
Definition: avcodec.h:2284
AVCodec
AVCodec.
Definition: codec.h:197
AVMEDIA_TYPE_SUBTITLE
@ AVMEDIA_TYPE_SUBTITLE
Definition: avutil.h:204
FF_CODEC_CAP_INIT_THREADSAFE
#define FF_CODEC_CAP_INIT_THREADSAFE
The codec does not modify any global variables in the init function, allowing to call the init functi...
Definition: internal.h:42
AVERROR
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
color
Definition: vf_paletteuse.c:587
sub
static float sub(float src0, float src1)
Definition: dnn_backend_native_layer_mathbinary.c:31
AV_TIME_BASE_Q
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition: avutil.h:260
w
uint8_t w
Definition: llviddspenc.c:38
internal.h
AVPacket::data
uint8_t * data
Definition: packet.h:373
data
const char data[16]
Definition: mxf.c:143
mathematics.h
av_malloc
#define av_malloc(s)
Definition: tableprint_vlc.h:31
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
tc_muls
static const uint8_t tc_muls[9]
Definition: xsubdec.c:35
GetBitContext
Definition: get_bits.h:62
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
av_cold
#define av_cold
Definition: attributes.h:90
init_get_bits8
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:678
parse_timecode
static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time)
Definition: xsubdec.c:37
decode_init
static av_cold int decode_init(AVCodecContext *avctx)
Definition: xsubdec.c:29
get_bits.h
av_rescale_q
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:141
run
uint8_t run
Definition: svq3.c:203
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
AVPALETTE_SIZE
#define AVPALETTE_SIZE
Definition: pixfmt.h:32
tc_offsets
static const uint8_t tc_offsets[9]
Definition: xsubdec.c:34
c
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
ff_log2_tab
const uint8_t ff_log2_tab[256]
Definition: log2_tab.c:23
for
for(j=16;j >0;--j)
Definition: h264pred_template.c:469
AVPacket::size
int size
Definition: packet.h:374
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
SUBTITLE_BITMAP
@ SUBTITLE_BITMAP
A bitmap, pict will be set.
Definition: avcodec.h:2239
i
int i
Definition: input.c:406
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:366
show_bits
static unsigned int show_bits(GetBitContext *s, int n)
Show 1-25 bits.
Definition: get_bits.h:447
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
av_mallocz
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:261
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:204
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:589
log2
#define log2(x)
Definition: libm.h:404
AV_CODEC_ID_XSUB
@ AV_CODEC_ID_XSUB
Definition: codec_id.h:524
avcodec.h
AV_PIX_FMT_PAL8
@ AV_PIX_FMT_PAL8
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:77
ret
ret
Definition: filter_design.txt:187
align_get_bits
static const uint8_t * align_get_bits(GetBitContext *s)
Definition: get_bits.h:694
AVCodecContext
main external API structure.
Definition: avcodec.h:379
AVCodecContext::codec_tag
unsigned int codec_tag
fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
Definition: avcodec.h:404
AVPacket
This structure stores compressed data.
Definition: packet.h:350
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:35
bytestream.h
imgutils.h
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
decode_frame
static int decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr, AVPacket *avpkt)
Definition: xsubdec.c:50
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
MKTAG
#define MKTAG(a, b, c, d)
Definition: macros.h:55
h
h
Definition: vp9dsp_template.c:2038
av_image_check_size
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:318
ff_xsub_decoder
const AVCodec ff_xsub_decoder
Definition: xsubdec.c:163