FFmpeg: libavcodec/xsubdec.c Source File

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libavcodec

xsubdec.c

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1 /*

2 * XSUB subtitle decoder

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 */

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"

30 static av_cold int decode_init(AVCodecContext *avctx) {

31 avctx->pix_fmt = AV_PIX_FMT_PAL8;

32 return 0;

33 }

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 };

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 }

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;

56 AVSubtitleRect *rect;

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 int64_t start_display_time, end_display_time;

65 // check that at least header fits

66 if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {

67 av_log(avctx, AV_LOG_ERROR, "coded frame size %d too small\n", buf_size);

68 return -1;

69 }

71 // read start and end time

72 if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {

73 av_log(avctx, AV_LOG_ERROR, "invalid time code\n");

74 return -1;

75 }

76 if (avpkt->pts != AV_NOPTS_VALUE)

77 packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});

79 sub->start_display_time = start_display_time = parse_timecode(buf + 1, packet_time);

80 sub->end_display_time = end_display_time = parse_timecode(buf + 14, packet_time);

81 if (sub->start_display_time != start_display_time ||

82 sub-> end_display_time != end_display_time) {

83 av_log(avctx, AV_LOG_ERROR, "time code not representable in 32bit\n");

84 return -1;

85 }

86 buf += 27;

88 // read header

89 w = bytestream_get_le16(&buf);

90 h = bytestream_get_le16(&buf);

91 if (av_image_check_size(w, h, 0, avctx) < 0)

92 return -1;

93 x = bytestream_get_le16(&buf);

94 y = bytestream_get_le16(&buf);

95 // skip bottom right position, it gives no new information

96 bytestream_get_le16(&buf);

97 bytestream_get_le16(&buf);

98 // The following value is supposed to indicate the start offset

99 // (relative to the palette) of the data for the second field,

100 // however there are files in which it has a bogus value and thus

101 // we just ignore it

102 bytestream_get_le16(&buf);

103

104 if (buf_end - buf < h + 3*4)

105 return AVERROR_INVALIDDATA;

106

107 // allocate sub and set values

108 sub->rects = av_mallocz(sizeof(*sub->rects));

109 if (!sub->rects)

110 return AVERROR(ENOMEM);

111

112 sub->rects[0] = rect = av_mallocz(sizeof(*sub->rects[0]));

113 if (!sub->rects[0])

114 return AVERROR(ENOMEM);

115 sub->num_rects = 1;

116 rect->x = x; rect->y = y;

117 rect->w = w; rect->h = h;

118 rect->type = SUBTITLE_BITMAP;

119 rect->linesize[0] = w;

120 rect->data[0] = av_malloc(w * h);

121 rect->nb_colors = 4;

122 rect->data[1] = av_mallocz(AVPALETTE_SIZE);

123 if (!rect->data[0] || !rect->data[1])

124 return AVERROR(ENOMEM);

125

126 // read palette

127 for (i = 0; i < rect->nb_colors; i++)

128 ((uint32_t*)rect->data[1])[i] = bytestream_get_be24(&buf);

129

130 if (!has_alpha) {

131 // make all except background (first entry) non-transparent

132 for (i = 1; i < rect->nb_colors; i++)

133 ((uint32_t *)rect->data[1])[i] |= 0xff000000;

134 } else {

135 for (i = 0; i < rect->nb_colors; i++)

136 ((uint32_t *)rect->data[1])[i] |= (unsigned)*buf++ << 24;

137 }

138

139 // process RLE-compressed data

140 if ((ret = init_get_bits8(&gb, buf, buf_end - buf)) < 0)

141 return ret;

142 bitmap = rect->data[0];

143 for (y = 0; y < h; y++) {

144 // interlaced: do odd lines

145 if (y == (h + 1) / 2) bitmap = rect->data[0] + w;

146 for (x = 0; x < w; ) {

147 int log2 = ff_log2_tab[show_bits(&gb, 8)];

148 int run = get_bits(&gb, 14 - 4 * (log2 >> 1));

149 int color = get_bits(&gb, 2);

150 run = FFMIN(run, w - x);

151 // run length 0 means till end of row

152 if (!run) run = w - x;

153 memset(bitmap, color, run);

154 bitmap += run;

155 x += run;

156 }

157 // interlaced, skip every second line

158 bitmap += w;

159 align_get_bits(&gb);

160 }

161 *got_sub_ptr = 1;

162 return buf_size;

163 }

164

165 const FFCodec ff_xsub_decoder = {

166 .p.name = "xsub",

167 CODEC_LONG_NAME("XSUB"),

168 .p.type = AVMEDIA_TYPE_SUBTITLE,

169 .p.id = AV_CODEC_ID_XSUB,

170 .init = decode_init,

171 FF_CODEC_DECODE_SUB_CB(decode_frame),

172 };

AVSubtitle

Definition: avcodec.h:2082

rect::w

int w

Definition: f_ebur128.c:78

AVMEDIA_TYPE_SUBTITLE

@ AVMEDIA_TYPE_SUBTITLE

Definition: avutil.h:203

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:2087

color

Definition: vf_paletteuse.c:513

rect

Definition: f_ebur128.c:78

AV_TIME_BASE_Q

#define AV_TIME_BASE_Q

Internal time base represented as fractional value.

Definition: avutil.h:263

int64_t

long long int64_t

Definition: coverity.c:34

AVSubtitleRect

Definition: avcodec.h:2055

AVSubtitle::num_rects

unsigned num_rects

Definition: avcodec.h:2086

rect::y

int y

Definition: f_ebur128.c:78

uint8_t w

Definition: llviddspenc.c:38

AVPacket::data

uint8_t * data

Definition: packet.h:558

FFCodec

Definition: codec_internal.h:127

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:333

tc_muls

static const uint8_t tc_muls[9]

Definition: xsubdec.c:36

FFCodec::p

AVCodec p

The public AVCodec.

Definition: codec_internal.h:131

GetBitContext

Definition: get_bits.h:109

AV_LOG_ERROR

#define AV_LOG_ERROR

Something went wrong and cannot losslessly be recovered.

Definition: log.h:210

av_cold

#define av_cold

Definition: attributes.h:106

init_get_bits8

static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)

Initialize GetBitContext.

Definition: get_bits.h:539

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:165

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:331

run

uint8_t run

Definition: svq3.c:207

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

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:559

codec_internal.h

for

for(k=2;k<=8;++k)

Definition: h264pred_template.c:424

AV_NOPTS_VALUE