FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/xsubenc.c
Date: 2026-09-24 20:08:24
Exec Total Coverage
Lines: 0 85 0.0%
Functions: 0 5 0.0%
Branches: 0 48 0.0%
Line Branch Exec Source
1 /*
2 * DivX (XSUB) subtitle encoder
3 * Copyright (c) 2005 DivX, Inc.
4 * Copyright (c) 2009 Bjorn Axelsson
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #include "avcodec.h"
24 #include "bytestream.h"
25 #include "codec_internal.h"
26 #include "put_bits.h"
27
28 /**
29 * Number of pixels to pad left and right.
30 *
31 * The official encoder pads the subtitles with two pixels on either side,
32 * but until we find out why, we won't do it (we will pad to have width
33 * divisible by 2 though).
34 */
35 #define PADDING 0
36 #define PADDING_COLOR 0
37
38 /**
39 * Encode a single color run. At most 16 bits will be used.
40 * @param len length of the run, values > 255 mean "until end of line", may not be < 0.
41 * @param color color to encode, only the lowest two bits are used and all others must be 0.
42 */
43 ✗ static void put_xsub_rle(PutBitContext *pb, int len, int color)
44 {
45 ✗ if (len <= 255)
46 ✗ put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
47 else
48 ✗ put_bits(pb, 14, 0);
49 ✗ put_bits(pb, 2, color);
50 ✗ }
51
52 /**
53 * Encode a 4-color bitmap with XSUB rle.
54 *
55 * The encoded bitmap may be wider than the source bitmap due to padding.
56 */
57 ✗ static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
58 int linesize, int w, int h)
59 {
60 ✗ int x0, x1, y, len, color = PADDING_COLOR;
61
62 ✗ for (y = 0; y < h; y++) {
63 ✗ x0 = 0;
64 ✗ while (x0 < w) {
65 // Make sure we have enough room for at least one run and padding
66 ✗ if (put_bytes_left(pb, 1) < 7)
67 ✗ return AVERROR_BUFFER_TOO_SMALL;
68
69 ✗ x1 = x0;
70 ✗ color = bitmap[x1++] & 3;
71 ✗ while (x1 < w && (bitmap[x1] & 3) == color)
72 ✗ x1++;
73 ✗ len = x1 - x0;
74 if (PADDING && x0 == 0) {
75 if (color == PADDING_COLOR) {
76 len += PADDING;
77 x0 -= PADDING;
78 } else
79 put_xsub_rle(pb, PADDING, PADDING_COLOR);
80 }
81
82 // Run can't be longer than 255, unless it is the rest of a row
83 ✗ if (x1 == w && color == PADDING_COLOR) {
84 ✗ len += PADDING + (w&1);
85 } else
86 ✗ len = FFMIN(len, 255);
87 ✗ put_xsub_rle(pb, len, color);
88
89 ✗ x0 += len;
90 }
91 ✗ if (color != PADDING_COLOR && (PADDING + (w&1)))
92 ✗ put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);
93
94 ✗ align_put_bits(pb);
95
96 ✗ bitmap += linesize;
97 }
98
99 ✗ return 0;
100 }
101
102 ✗ static int make_tc(uint64_t ms, int *tc)
103 {
104 static const int tc_divs[3] = { 1000, 60, 60 };
105 int i;
106 ✗ for (i=0; i<3; i++) {
107 ✗ tc[i] = ms % tc_divs[i];
108 ✗ ms /= tc_divs[i];
109 }
110 ✗ tc[3] = ms;
111 ✗ return ms > 99;
112 }
113
114 ✗ static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
115 int bufsize, const AVSubtitle *h)
116 {
117 ✗ uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
118 ✗ uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
119 int start_tc[4], end_tc[4];
120 ✗ uint8_t *hdr = buf + 27; // Point behind the timestamp
121 uint8_t *rlelenptr;
122 uint16_t width, height;
123 int i;
124 PutBitContext pb;
125
126 ✗ if (bufsize < 27 + 7*2 + 4*3) {
127 ✗ av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
128 ✗ return AVERROR_BUFFER_TOO_SMALL;
129 }
130
131 // TODO: support multiple rects
132 ✗ if (h->num_rects != 1)
133 ✗ av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
134
135 // TODO: render text-based subtitles into bitmaps
136 ✗ if (!h->rects[0]->data[0] || !h->rects[0]->data[1]) {
137 ✗ av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
138 ✗ return AVERROR(EINVAL);
139 }
140
141 // TODO: color reduction, similar to dvdsub encoder
142 ✗ if (h->rects[0]->nb_colors > 4)
143 ✗ av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
144
145 // TODO: Palette swapping if color zero is not transparent
146 ✗ if (((uint32_t *)h->rects[0]->data[1])[0] & 0xff000000)
147 ✗ av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
148
149 ✗ if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
150 ✗ av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
151 ✗ return AVERROR(EINVAL);
152 }
153
154 ✗ snprintf(buf, 28,
155 "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
156 start_tc[3], start_tc[2], start_tc[1], start_tc[0],
157 end_tc[3], end_tc[2], end_tc[1], end_tc[0]);
158
159 // Width and height must probably be multiples of 2.
160 // 2 pixels required on either side of subtitle.
161 // Possibly due to limitations of hardware renderers.
162 // TODO: check if the bitmap is already padded
163 ✗ width = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
164 ✗ height = FFALIGN(h->rects[0]->h, 2);
165
166 ✗ bytestream_put_le16(&hdr, width);
167 ✗ bytestream_put_le16(&hdr, height);
168 ✗ bytestream_put_le16(&hdr, h->rects[0]->x);
169 ✗ bytestream_put_le16(&hdr, h->rects[0]->y);
170 ✗ bytestream_put_le16(&hdr, h->rects[0]->x + width -1);
171 ✗ bytestream_put_le16(&hdr, h->rects[0]->y + height -1);
172
173 ✗ rlelenptr = hdr; // Will store length of first field here later.
174 ✗ hdr+=2;
175
176 // Palette
177 ✗ for (i=0; i<4; i++)
178 ✗ bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->data[1])[i]);
179
180 // Bitmap
181 // RLE buffer. Reserve 2 bytes for possible padding after the last row.
182 ✗ init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
183 ✗ if (xsub_encode_rle(&pb, h->rects[0]->data[0],
184 ✗ h->rects[0]->linesize[0] * 2,
185 ✗ h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
186 ✗ return AVERROR_BUFFER_TOO_SMALL;
187 ✗ bytestream_put_le16(&rlelenptr, put_bytes_count(&pb, 0)); // Length of first field
188
189 ✗ if (xsub_encode_rle(&pb, h->rects[0]->data[0] + h->rects[0]->linesize[0],
190 ✗ h->rects[0]->linesize[0] * 2,
191 ✗ h->rects[0]->w, h->rects[0]->h >> 1))
192 ✗ return AVERROR_BUFFER_TOO_SMALL;
193
194 // Enforce total height to be a multiple of 2
195 ✗ if (h->rects[0]->h & 1) {
196 ✗ put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
197 }
198
199 ✗ flush_put_bits(&pb);
200
201 ✗ return hdr - buf + put_bytes_output(&pb);
202 }
203
204 ✗ static av_cold int xsub_encoder_init(AVCodecContext *avctx)
205 {
206 ✗ if (!avctx->codec_tag)
207 ✗ avctx->codec_tag = MKTAG('D','X','S','B');
208
209 ✗ avctx->bits_per_coded_sample = 4;
210
211 ✗ return 0;
212 }
213
214 const FFCodec ff_xsub_encoder = {
215 .p.name = "xsub",
216 CODEC_LONG_NAME("DivX subtitles (XSUB)"),
217 .p.type = AVMEDIA_TYPE_SUBTITLE,
218 .p.id = AV_CODEC_ID_XSUB,
219 .init = xsub_encoder_init,
220 FF_CODEC_ENCODE_SUB_CB(xsub_encode),
221 };
222