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 "libavutil/mem.h"
25 #include "avcodec.h"
26 #include "get_bits.h"
27 #include "bytestream.h"
28 #include "codec_internal.h"
29 
30 static av_cold int decode_init(AVCodecContext *avctx) {
31  avctx->pix_fmt = AV_PIX_FMT_PAL8;
32  return 0;
33 }
34 
35 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
36 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
37 
38 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
39  int i;
40  int64_t ms = 0;
41  if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
42  return AV_NOPTS_VALUE;
43  for (i = 0; i < sizeof(tc_offsets); i++) {
44  uint8_t c = buf[tc_offsets[i]] - '0';
45  if (c > 9) return AV_NOPTS_VALUE;
46  ms = (ms + c) * tc_muls[i];
47  }
48  return ms - packet_time;
49 }
50 
51 static int decode_frame(AVCodecContext *avctx, AVSubtitle *sub,
52  int *got_sub_ptr, const AVPacket *avpkt)
53 {
54  const uint8_t *buf = avpkt->data;
55  int buf_size = avpkt->size;
57  const uint8_t *buf_end = buf + buf_size;
58  uint8_t *bitmap;
59  int w, h, x, y, i, ret;
60  int64_t packet_time = 0;
61  GetBitContext gb;
62  int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
63 
64  // check that at least header fits
65  if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
66  av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);
67  return -1;
68  }
69 
70  // read start and end time
71  if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
72  av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
73  return -1;
74  }
75  if (avpkt->pts != AV_NOPTS_VALUE)
76  packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
77  sub->start_display_time = parse_timecode(buf + 1, packet_time);
78  sub->end_display_time = parse_timecode(buf + 14, packet_time);
79  buf += 27;
80 
81  // read header
82  w = bytestream_get_le16(&buf);
83  h = bytestream_get_le16(&buf);
84  if (av_image_check_size(w, h, 0, avctx) < 0)
85  return -1;
86  x = bytestream_get_le16(&buf);
87  y = bytestream_get_le16(&buf);
88  // skip bottom right position, it gives no new information
89  bytestream_get_le16(&buf);
90  bytestream_get_le16(&buf);
91  // The following value is supposed to indicate the start offset
92  // (relative to the palette) of the data for the second field,
93  // however there are files in which it has a bogus value and thus
94  // we just ignore it
95  bytestream_get_le16(&buf);
96 
97  if (buf_end - buf < h + 3*4)
98  return AVERROR_INVALIDDATA;
99 
100  // allocate sub and set values
101  sub->rects = av_mallocz(sizeof(*sub->rects));
102  if (!sub->rects)
103  return AVERROR(ENOMEM);
104 
105  sub->rects[0] = rect = av_mallocz(sizeof(*sub->rects[0]));
106  if (!sub->rects[0])
107  return AVERROR(ENOMEM);
108  sub->num_rects = 1;
109  rect->x = x; rect->y = y;
110  rect->w = w; rect->h = h;
111  rect->type = SUBTITLE_BITMAP;
112  rect->linesize[0] = w;
113  rect->data[0] = av_malloc(w * h);
114  rect->nb_colors = 4;
115  rect->data[1] = av_mallocz(AVPALETTE_SIZE);
116  if (!rect->data[0] || !rect->data[1])
117  return AVERROR(ENOMEM);
118 
119  // read palette
120  for (i = 0; i < rect->nb_colors; i++)
121  ((uint32_t*)rect->data[1])[i] = bytestream_get_be24(&buf);
122 
123  if (!has_alpha) {
124  // make all except background (first entry) non-transparent
125  for (i = 1; i < rect->nb_colors; i++)
126  ((uint32_t *)rect->data[1])[i] |= 0xff000000;
127  } else {
128  for (i = 0; i < rect->nb_colors; i++)
129  ((uint32_t *)rect->data[1])[i] |= (unsigned)*buf++ << 24;
130  }
131 
132  // process RLE-compressed data
133  if ((ret = init_get_bits8(&gb, buf, buf_end - buf)) < 0)
134  return ret;
135  bitmap = rect->data[0];
136  for (y = 0; y < h; y++) {
137  // interlaced: do odd lines
138  if (y == (h + 1) / 2) bitmap = rect->data[0] + w;
139  for (x = 0; x < w; ) {
140  int log2 = ff_log2_tab[show_bits(&gb, 8)];
141  int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
142  int color = get_bits(&gb, 2);
143  run = FFMIN(run, w - x);
144  // run length 0 means till end of row
145  if (!run) run = w - x;
146  memset(bitmap, color, run);
147  bitmap += run;
148  x += run;
149  }
150  // interlaced, skip every second line
151  bitmap += w;
152  align_get_bits(&gb);
153  }
154  *got_sub_ptr = 1;
155  return buf_size;
156 }
157 
159  .p.name = "xsub",
160  CODEC_LONG_NAME("XSUB"),
161  .p.type = AVMEDIA_TYPE_SUBTITLE,
162  .p.id = AV_CODEC_ID_XSUB,
163  .init = decode_init,
165 };
AVSubtitle
Definition: avcodec.h:2228
rect::w
int w
Definition: f_ebur128.c:77
AVMEDIA_TYPE_SUBTITLE
@ AVMEDIA_TYPE_SUBTITLE
Definition: avutil.h:204
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
AVSubtitle::rects
AVSubtitleRect ** rects
Definition: avcodec.h:2233
color
Definition: vf_paletteuse.c:512
rect
Definition: f_ebur128.c:77
AV_TIME_BASE_Q
#define AV_TIME_BASE_Q
Internal time base represented as fractional value.
Definition: avutil.h:264
AVSubtitleRect
Definition: avcodec.h:2201
AVSubtitle::num_rects
unsigned num_rects
Definition: avcodec.h:2232
rect::y
int y
Definition: f_ebur128.c:77
w
uint8_t w
Definition: llviddspenc.c:38
AVPacket::data
uint8_t * data
Definition: packet.h:520
FFCodec
Definition: codec_internal.h:126
mathematics.h
av_malloc
#define av_malloc(s)
Definition: tableprint_vlc.h:30
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:335
tc_muls
static const uint8_t tc_muls[9]
Definition: xsubdec.c:36
FFCodec::p
AVCodec p
The public AVCodec.
Definition: codec_internal.h:130
GetBitContext
Definition: get_bits.h:108
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:545
parse_timecode
static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time)
Definition: xsubdec.c:38
decode_init
static av_cold int decode_init(AVCodecContext *avctx)
Definition: xsubdec.c:30
ff_xsub_decoder
const FFCodec ff_xsub_decoder
Definition: xsubdec.c:158
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:142
CODEC_LONG_NAME
#define CODEC_LONG_NAME(str)
Definition: codec_internal.h:271
run
uint8_t run
Definition: svq3.c:204
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:35
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
AVPacket::size
int size
Definition: packet.h:521
codec_internal.h
for
for(k=2;k<=8;++k)
Definition: h264pred_template.c:425
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
rect::h
int h
Definition: f_ebur128.c:77
AVSubtitle::end_display_time
uint32_t end_display_time
Definition: avcodec.h:2231
decode_frame
static int decode_frame(AVCodecContext *avctx, AVSubtitle *sub, int *got_sub_ptr, const AVPacket *avpkt)
Definition: xsubdec.c:51
rect::x
int x
Definition: f_ebur128.c:77
SUBTITLE_BITMAP
@ SUBTITLE_BITMAP
A bitmap, pict will be set.
Definition: avcodec.h:2184
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:256
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:513
show_bits
static unsigned int show_bits(GetBitContext *s, int n)
Show 1-25 bits.
Definition: get_bits.h:371
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:256
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:194
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:657
log2
#define log2(x)
Definition: libm.h:404
AV_CODEC_ID_XSUB
@ AV_CODEC_ID_XSUB
Definition: codec_id.h:553
avcodec.h
AV_PIX_FMT_PAL8
@ AV_PIX_FMT_PAL8
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:84
ret
ret
Definition: filter_design.txt:187
align_get_bits
static const uint8_t * align_get_bits(GetBitContext *s)
Definition: get_bits.h:561
AVCodecContext
main external API structure.
Definition: avcodec.h:445
FF_CODEC_DECODE_SUB_CB
#define FF_CODEC_DECODE_SUB_CB(func)
Definition: codec_internal.h:289
mem.h
AVCodecContext::codec_tag
unsigned int codec_tag
fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
Definition: avcodec.h:470
AVPacket
This structure stores compressed data.
Definition: packet.h:497
bytestream.h
imgutils.h
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
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
AVSubtitle::start_display_time
uint32_t start_display_time
Definition: avcodec.h:2230