FFmpeg: libavcodec/xsubdec.c Source File

FFmpeg

[フレーム]

libavcodec

xsubdec.c

Go to the documentation of this file.

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 "avcodec.h"

25 #include "get_bits.h"

26 #include "bytestream.h"

27 #include "internal.h"

29 static av_cold int decode_init(AVCodecContext *avctx) {

30 avctx->pix_fmt = AV_PIX_FMT_PAL8;

31 return 0;

32 }

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 };

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 }

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 AVSubtitleRect *rect;

56 const uint8_t *buf_end = buf + buf_size;

57 uint8_t *bitmap;

58 int w, h, x, y, i, ret;

59 int64_t packet_time = 0;

60 GetBitContext gb;

61 int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');

63 // check that at least header fits

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

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

66 return -1;

67 }

69 // read start and end time

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

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

72 return -1;

73 }

74 if (avpkt->pts != AV_NOPTS_VALUE)

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

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

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

78 buf += 27;

80 // read header

81 w = bytestream_get_le16(&buf);

82 h = bytestream_get_le16(&buf);

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

84 return -1;

85 x = bytestream_get_le16(&buf);

86 y = bytestream_get_le16(&buf);

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

88 bytestream_get_le16(&buf);

89 bytestream_get_le16(&buf);

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

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

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

93 // we just ignore it

94 bytestream_get_le16(&buf);

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

97 return AVERROR_INVALIDDATA;

99 // allocate sub and set values

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

101 if (!sub->rects)

102 return AVERROR(ENOMEM);

103

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

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

106 return AVERROR(ENOMEM);

107 sub->num_rects = 1;

108 rect->x = x; rect->y = y;

109 rect->w = w; rect->h = h;

110 rect->type = SUBTITLE_BITMAP;

111 rect->linesize[0] = w;

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

113 rect->nb_colors = 4;

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

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

116 return AVERROR(ENOMEM);

117

118 // read palette

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

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

121

122 if (!has_alpha) {

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

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

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

126 } else {

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

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

129 }

130

131 // process RLE-compressed data

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

133 return ret;

134 bitmap = rect->data[0];

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

136 // interlaced: do odd lines

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

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

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

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

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

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

143 // run length 0 means till end of row

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

145 memset(bitmap, color, run);

146 bitmap += run;

147 x += run;

148 }

149 // interlaced, skip every second line

150 bitmap += w;

151 align_get_bits(&gb);

152 }

153 *got_sub_ptr = 1;

154 return buf_size;

155 }

156

157 const AVCodec ff_xsub_decoder = {

158 .name = "xsub",

159 .long_name = NULL_IF_CONFIG_SMALL("XSUB"),

160 .type = AVMEDIA_TYPE_SUBTITLE,

161 .id = AV_CODEC_ID_XSUB,

162 .init = decode_init,

163 .decode = decode_frame,

164 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,

165 };

AVSubtitle

Definition: avcodec.h:2289

rect::w

int w

Definition: f_ebur128.c:77

AVCodec

AVCodec.

Definition: codec.h:202

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:599

sub

static float sub(float src0, float src1)

Definition: dnn_backend_native_layer_mathbinary.c:31

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:260

AVSubtitleRect

Definition: avcodec.h:2261

rect::y

int y

Definition: f_ebur128.c:77

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

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)