1 /*
2  * 3GPP TS 26.245 Timed Text decoder
3  * Copyright (c) 2012  Philip Langdale <philipl@overt.org>
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 "avcodec.h"
23 #include "ass.h"
24 #include "libavutil/opt.h"
25 #include "libavutil/avstring.h"
26 #include "libavutil/common.h"
27 #include "libavutil/bprint.h"
28 #include "libavutil/intreadwrite.h"
29 #include "libavutil/mem.h"
30 #include "bytestream.h"
31 #include "codec_internal.h"
32 
33 #define STYLE_FLAG_BOLD         (1<<0)
34 #define STYLE_FLAG_ITALIC       (1<<1)
35 #define STYLE_FLAG_UNDERLINE    (1<<2)
36 
37 #define BOX_SIZE_INITIAL    40
38 
39 #define STYL_BOX   (1<<0)
40 #define HLIT_BOX   (1<<1)
41 #define HCLR_BOX   (1<<2)
42 #define TWRP_BOX   (1<<3)
43 
44 #define BOTTOM_LEFT     1
45 #define BOTTOM_CENTER   2
46 #define BOTTOM_RIGHT    3
47 #define MIDDLE_LEFT     4
48 #define MIDDLE_CENTER   5
49 #define MIDDLE_RIGHT    6
50 #define TOP_LEFT        7
51 #define TOP_CENTER      8
52 #define TOP_RIGHT       9
53 
54 #define RGB_TO_BGR(c) (((c) & 0xff) << 16 | ((c) & 0xff00) | (((c) >> 16) & 0xff))
55 
56 typedef struct {
57     uint16_t font_id;
58     char *font;
59 } FontRecord;
60 
61 typedef struct {
62     uint16_t start;
63     uint16_t end;
64     uint8_t flags;
65     uint8_t bold;
66     uint8_t italic;
67     uint8_t underline;
68     int color;
69     uint8_t alpha;
70     uint8_t fontsize;
71     uint16_t font_id;
72 } StyleBox;
73 
74 typedef struct {
75     StyleBox style;
76     const char *font;
77     int back_color;
78     uint8_t back_alpha;
79     int alignment;
80 } MovTextDefault;
81 
82 typedef struct {
83     uint16_t hlit_start;
84     uint16_t hlit_end;
85 } HighlightBox;
86 
87 typedef struct {
88    uint8_t hlit_color[4];
89 } HilightcolorBox;
90 
91 typedef struct {
92     uint8_t wrap_flag;
93 } TextWrapBox;
94 
95 typedef struct {
96     AVClass *class;
97     StyleBox *s;
98     HighlightBox h;
99     HilightcolorBox c;
100     FontRecord *ftab;
101     TextWrapBox w;
102     MovTextDefault d;
103     uint8_t box_flags;
104     uint16_t style_entries, ftab_entries;
105     int readorder;
106     int frame_width;
107     int frame_height;
108 } MovTextContext;
109 
110 typedef struct {
111     uint32_t type;
112     unsigned base_size;
113     int (*decode)(const uint8_t *tsmb, MovTextContext *m, uint64_t size);
114 } Box;
115 
mov_text_cleanup(MovTextContext *m)116 static void mov_text_cleanup(MovTextContext *m)
117 {
118     if (m->box_flags & STYL_BOX) {
119         av_freep(&m->s);
120         m->style_entries = 0;
121     }
122 }
123 
mov_text_cleanup_ftab(MovTextContext *m)124 static void mov_text_cleanup_ftab(MovTextContext *m)
125 {
126     for (unsigned i = 0; i < m->ftab_entries; i++)
127         av_freep(&m->ftab[i].font);
128     av_freep(&m->ftab);
129     m->ftab_entries = 0;
130 }
131 
mov_text_parse_style_record(StyleBox *style, const uint8_t **ptr)132 static void mov_text_parse_style_record(StyleBox *style, const uint8_t **ptr)
133 {
134     // fontID
135     style->font_id   = bytestream_get_be16(ptr);
136     // face-style-flags
137     style->flags     = bytestream_get_byte(ptr);
138     style->bold      = !!(style->flags & STYLE_FLAG_BOLD);
139     style->italic    = !!(style->flags & STYLE_FLAG_ITALIC);
140     style->underline = !!(style->flags & STYLE_FLAG_UNDERLINE);
141     // fontsize
142     style->fontsize  = bytestream_get_byte(ptr);
143     // Primary color
144     style->color     = bytestream_get_be24(ptr);
145     style->color     = RGB_TO_BGR(style->color);
146     style->alpha     = bytestream_get_byte(ptr);
147 }
148 
mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)149 static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
150 {
151     const uint8_t *tx3g_ptr = avctx->extradata;
152     int i, j = -1, font_length, remaining = avctx->extradata_size - BOX_SIZE_INITIAL;
153     int8_t v_align, h_align;
154     unsigned ftab_entries;
155 
156     m->ftab_entries = 0;
157     if (remaining < 0)
158         return -1;
159 
160     // Display Flags
161     tx3g_ptr += 4;
162     // Alignment
163     h_align = bytestream_get_byte(&tx3g_ptr);
164     v_align = bytestream_get_byte(&tx3g_ptr);
165     if (h_align == 0) {
166         if (v_align == 0)
167             m->d.alignment = TOP_LEFT;
168         if (v_align == 1)
169             m->d.alignment = MIDDLE_LEFT;
170         if (v_align == -1)
171             m->d.alignment = BOTTOM_LEFT;
172     }
173     if (h_align == 1) {
174         if (v_align == 0)
175             m->d.alignment = TOP_CENTER;
176         if (v_align == 1)
177             m->d.alignment = MIDDLE_CENTER;
178         if (v_align == -1)
179             m->d.alignment = BOTTOM_CENTER;
180     }
181     if (h_align == -1) {
182         if (v_align == 0)
183             m->d.alignment = TOP_RIGHT;
184         if (v_align == 1)
185             m->d.alignment = MIDDLE_RIGHT;
186         if (v_align == -1)
187             m->d.alignment = BOTTOM_RIGHT;
188     }
189     // Background Color
190     m->d.back_color = bytestream_get_be24(&tx3g_ptr);
191     m->d.back_color = RGB_TO_BGR(m->d.back_color);
192     m->d.back_alpha = bytestream_get_byte(&tx3g_ptr);
193     // BoxRecord
194     tx3g_ptr += 8;
195     // StyleRecord
196     tx3g_ptr += 4;
197     mov_text_parse_style_record(&m->d.style, &tx3g_ptr);
198     // FontRecord
199     // FontRecord Size
200     tx3g_ptr += 4;
201     // ftab
202     tx3g_ptr += 4;
203 
204     // In case of broken header, init default font
205     m->d.font = ASS_DEFAULT_FONT;
206 
207     ftab_entries = bytestream_get_be16(&tx3g_ptr);
208     if (!ftab_entries)
209         return 0;
210     remaining   -= 3 * ftab_entries;
211     if (remaining < 0)
212         return AVERROR_INVALIDDATA;
213     m->ftab = av_calloc(ftab_entries, sizeof(*m->ftab));
214     if (!m->ftab)
215         return AVERROR(ENOMEM);
216     m->ftab_entries = ftab_entries;
217 
218     for (i = 0; i < m->ftab_entries; i++) {
219         m->ftab[i].font_id = bytestream_get_be16(&tx3g_ptr);
220         if (m->ftab[i].font_id == m->d.style.font_id)
221             j = i;
222         font_length = bytestream_get_byte(&tx3g_ptr);
223 
224         remaining  -= font_length;
225         if (remaining < 0) {
226             mov_text_cleanup_ftab(m);
227             return -1;
228         }
229         m->ftab[i].font = av_malloc(font_length + 1);
230         if (!m->ftab[i].font) {
231             mov_text_cleanup_ftab(m);
232             return AVERROR(ENOMEM);
233         }
234         bytestream_get_buffer(&tx3g_ptr, m->ftab[i].font, font_length);
235         m->ftab[i].font[font_length] = '\0';
236     }
237     if (j >= 0)
238         m->d.font = m->ftab[j].font;
239     return 0;
240 }
241 
decode_twrp(const uint8_t *tsmb, MovTextContext *m, uint64_t size)242 static int decode_twrp(const uint8_t *tsmb, MovTextContext *m, uint64_t size)
243 {
244     m->box_flags |= TWRP_BOX;
245     m->w.wrap_flag = bytestream_get_byte(&tsmb);
246     return 0;
247 }
248 
decode_hlit(const uint8_t *tsmb, MovTextContext *m, uint64_t size)249 static int decode_hlit(const uint8_t *tsmb, MovTextContext *m, uint64_t size)
250 {
251     m->box_flags |= HLIT_BOX;
252     m->h.hlit_start = bytestream_get_be16(&tsmb);
253     m->h.hlit_end   = bytestream_get_be16(&tsmb);
254     return 0;
255 }
256 
decode_hclr(const uint8_t *tsmb, MovTextContext *m, uint64_t size)257 static int decode_hclr(const uint8_t *tsmb, MovTextContext *m, uint64_t size)
258 {
259     m->box_flags |= HCLR_BOX;
260     bytestream_get_buffer(&tsmb, m->c.hlit_color, 4);
261     return 0;
262 }
263 
styles_equivalent(const StyleBox *a, const StyleBox *b)264 static int styles_equivalent(const StyleBox *a, const StyleBox *b)
265 {
266 #define CMP(field) ((a)->field == (b)->field)
267     return CMP(bold)  && CMP(italic)   && CMP(underline) && CMP(color) &&
268            CMP(alpha) && CMP(fontsize) && CMP(font_id);
269 #undef CMP
270 }
271 
decode_styl(const uint8_t *tsmb, MovTextContext *m, uint64_t size)272 static int decode_styl(const uint8_t *tsmb, MovTextContext *m, uint64_t size)
273 {
274     int i;
275     int style_entries = bytestream_get_be16(&tsmb);
276     StyleBox *tmp;
277 
278     // A single style record is of length 12 bytes.
279     if (2 + style_entries * 12 > size)
280         return -1;
281 
282     tmp = av_realloc_array(m->s, style_entries, sizeof(*m->s));
283     if (!tmp)
284         return AVERROR(ENOMEM);
285     m->s             = tmp;
286     m->style_entries = style_entries;
287 
288     m->box_flags |= STYL_BOX;
289     for(i = 0; i < m->style_entries; i++) {
290         StyleBox *style = &m->s[i];
291 
292         style->start = bytestream_get_be16(&tsmb);
293         style->end   = bytestream_get_be16(&tsmb);
294         if (style->end < style->start ||
295             (i && style->start < m->s[i - 1].end)) {
296             mov_text_cleanup(m);
297             return AVERROR_INVALIDDATA;
298         }
299         if (style->start == style->end) {
300             /* Skip this style as it applies to no character */
301             tsmb += 8;
302             m->style_entries--;
303             i--;
304             continue;
305         }
306 
307         mov_text_parse_style_record(style, &tsmb);
308         if (styles_equivalent(style, &m->d.style)) {
309             /* Skip this style as it is equivalent to the default style */
310             m->style_entries--;
311             i--;
312             continue;
313         } else if (i && style->start == style[-1].end &&
314                    styles_equivalent(style, &style[-1])) {
315             /* Merge the two adjacent styles */
316             style[-1].end = style->end;
317             m->style_entries--;
318             i--;
319             continue;
320         }
321     }
322     return 0;
323 }
324 
325 static const Box box_types[] = {
326     { MKBETAG('s','t','y','l'), 2, decode_styl },
327     { MKBETAG('h','l','i','t'), 4, decode_hlit },
328     { MKBETAG('h','c','l','r'), 4, decode_hclr },
329     { MKBETAG('t','w','r','p'), 1, decode_twrp }
330 };
331 
332 const static size_t box_count = FF_ARRAY_ELEMS(box_types);
333 
334 // Return byte length of the UTF-8 sequence starting at text[0]. 0 on error.
get_utf8_length_at(const char *text, const char *text_end)335 static int get_utf8_length_at(const char *text, const char *text_end)
336 {
337     const char *start = text;
338     int err = 0;
339     uint32_t c;
340     GET_UTF8(c, text < text_end ? (uint8_t)*text++ : (err = 1, 0), goto error;);
341     if (err)
342         goto error;
343     return text - start;
344 error:
345     return 0;
346 }
347 
text_to_ass(AVBPrint *buf, const char *text, const char *text_end, AVCodecContext *avctx)348 static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
349                        AVCodecContext *avctx)
350 {
351     MovTextContext *m = avctx->priv_data;
352     const StyleBox *const default_style = &m->d.style;
353     int i = 0;
354     int text_pos = 0;
355     int entry = 0;
356     int color = default_style->color;
357 
358     if (text < text_end && m->box_flags & TWRP_BOX) {
359         if (m->w.wrap_flag == 1) {
360             av_bprintf(buf, "{\\q1}"); /* End of line wrap */
361         } else {
362             av_bprintf(buf, "{\\q2}"); /* No wrap */
363         }
364     }
365 
366     while (text < text_end) {
367         int len;
368 
369         if ((m->box_flags & STYL_BOX) && entry < m->style_entries) {
370             const StyleBox *style = &m->s[entry];
371             if (text_pos == style->end) {
372                 av_bprintf(buf, "{\\r}");
373                 color = default_style->color;
374                 entry++;
375                 style++;
376             }
377             if (entry < m->style_entries && text_pos == style->start) {
378                 if (style->bold ^ default_style->bold)
379                     av_bprintf(buf, "{\\b%d}", style->bold);
380                 if (style->italic ^ default_style->italic)
381                     av_bprintf(buf, "{\\i%d}", style->italic);
382                 if (style->underline ^ default_style->underline)
383                     av_bprintf(buf, "{\\u%d}", style->underline);
384                 if (style->fontsize != default_style->fontsize)
385                     av_bprintf(buf, "{\\fs%d}", style->fontsize);
386                 if (style->font_id != default_style->font_id)
387                     for (i = 0; i < m->ftab_entries; i++) {
388                         if (style->font_id == m->ftab[i].font_id)
389                             av_bprintf(buf, "{\\fn%s}", m->ftab[i].font);
390                     }
391                 if (default_style->color != style->color) {
392                     color = style->color;
393                     av_bprintf(buf, "{\\1c&H%X&}", color);
394                 }
395                 if (default_style->alpha != style->alpha)
396                     av_bprintf(buf, "{\\1a&H%02X&}", 255 - style->alpha);
397             }
398         }
399         if (m->box_flags & HLIT_BOX) {
400             if (text_pos == m->h.hlit_start) {
401                 /* If hclr box is present, set the secondary color to the color
402                  * specified. Otherwise, set primary color to white and secondary
403                  * color to black. These colors will come from TextSampleModifier
404                  * boxes in future and inverse video technique for highlight will
405                  * be implemented.
406                  */
407                 if (m->box_flags & HCLR_BOX) {
408                     av_bprintf(buf, "{\\2c&H%02x%02x%02x&}", m->c.hlit_color[2],
409                                 m->c.hlit_color[1], m->c.hlit_color[0]);
410                 } else {
411                     av_bprintf(buf, "{\\1c&H000000&}{\\2c&HFFFFFF&}");
412                 }
413             }
414             if (text_pos == m->h.hlit_end) {
415                 if (m->box_flags & HCLR_BOX) {
416                     av_bprintf(buf, "{\\2c&H%X&}", default_style->color);
417                 } else {
418                     av_bprintf(buf, "{\\1c&H%X&}{\\2c&H%X&}",
419                                color, default_style->color);
420                 }
421             }
422         }
423 
424         len = get_utf8_length_at(text, text_end);
425         if (len < 1) {
426             av_log(avctx, AV_LOG_ERROR, "invalid UTF-8 byte in subtitle\n");
427             len = 1;
428         }
429         switch (*text) {
430         case '\r':
431             break;
432         case '\n':
433             av_bprintf(buf, "\\N");
434             break;
435         default:
436             av_bprint_append_data(buf, text, len);
437             break;
438         }
439         text += len;
440         text_pos++;
441     }
442 
443     return 0;
444 }
445 
mov_text_init(AVCodecContext *avctx)446 static int mov_text_init(AVCodecContext *avctx) {
447     /*
448      * TODO: Handle the default text style.
449      * NB: Most players ignore styles completely, with the result that
450      * it's very common to find files where the default style is broken
451      * and respecting it results in a worse experience than ignoring it.
452      */
453     int ret;
454     MovTextContext *m = avctx->priv_data;
455     ret = mov_text_tx3g(avctx, m);
456     if (ret == 0) {
457         const StyleBox *const default_style = &m->d.style;
458         if (!m->frame_width || !m->frame_height) {
459             m->frame_width = ASS_DEFAULT_PLAYRESX;
460             m->frame_height = ASS_DEFAULT_PLAYRESY;
461         }
462         return ff_ass_subtitle_header_full(avctx,
463                     m->frame_width, m->frame_height,
464                     m->d.font, default_style->fontsize,
465                     (255U - default_style->alpha) << 24 | default_style->color,
466                     (255U - default_style->alpha) << 24 | default_style->color,
467                     (255U - m->d.back_alpha) << 24 | m->d.back_color,
468                     (255U - m->d.back_alpha) << 24 | m->d.back_color,
469                     default_style->bold, default_style->italic, default_style->underline,
470                     ASS_DEFAULT_BORDERSTYLE, m->d.alignment);
471     } else
472         return ff_ass_subtitle_header_default(avctx);
473 }
474 
mov_text_decode_frame(AVCodecContext *avctx, AVSubtitle *sub, int *got_sub_ptr, const AVPacket *avpkt)475 static int mov_text_decode_frame(AVCodecContext *avctx, AVSubtitle *sub,
476                                  int *got_sub_ptr, const AVPacket *avpkt)
477 {
478     MovTextContext *m = avctx->priv_data;
479     int ret;
480     AVBPrint buf;
481     const char *ptr = avpkt->data, *end;
482     int text_length;
483     size_t i;
484 
485     if (!ptr || avpkt->size < 2)
486         return AVERROR_INVALIDDATA;
487 
488     /*
489      * A packet of size two with value zero is an empty subtitle
490      * used to mark the end of the previous non-empty subtitle.
491      * We can just drop them here as we have duration information
492      * already. If the value is non-zero, then it's technically a
493      * bad packet.
494      */
495     if (avpkt->size == 2)
496         return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;
497 
498     /*
499      * The first two bytes of the packet are the length of the text string
500      * In complex cases, there are style descriptors appended to the string
501      * so we can't just assume the packet size is the string size.
502      */
503     text_length = AV_RB16(ptr);
504     end = ptr + FFMIN(2 + text_length, avpkt->size);
505     ptr += 2;
506 
507     mov_text_cleanup(m);
508 
509     m->style_entries = 0;
510     m->box_flags = 0;
511     // Note that the spec recommends lines be no longer than 2048 characters.
512     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
513     if (text_length + 2 < avpkt->size) {
514         const uint8_t *tsmb = end;
515         const uint8_t *const tsmb_end = avpkt->data + avpkt->size;
516         // A box is a minimum of 8 bytes.
517         while (tsmb_end - tsmb >= 8) {
518             uint64_t tsmb_size = bytestream_get_be32(&tsmb);
519             uint32_t tsmb_type = bytestream_get_be32(&tsmb);
520             int size_var, ret_tsmb;
521 
522             if (tsmb_size == 1) {
523                 if (tsmb_end - tsmb < 8)
524                     break;
525                 tsmb_size = bytestream_get_be64(&tsmb);
526                 size_var = 16;
527             } else
528                 size_var = 8;
529             //size_var is equal to 8 or 16 depending on the size of box
530 
531             if (tsmb_size < size_var) {
532                 av_log(avctx, AV_LOG_ERROR, "tsmb_size invalid\n");
533                 return AVERROR_INVALIDDATA;
534             }
535             tsmb_size -= size_var;
536 
537             if (tsmb_end - tsmb < tsmb_size)
538                 break;
539 
540             for (i = 0; i < box_count; i++) {
541                 if (tsmb_type == box_types[i].type) {
542                     if (tsmb_size < box_types[i].base_size)
543                         break;
544                     ret_tsmb = box_types[i].decode(tsmb, m, tsmb_size);
545                     if (ret_tsmb == -1)
546                         break;
547                 }
548             }
549             tsmb += tsmb_size;
550         }
551         text_to_ass(&buf, ptr, end, avctx);
552         mov_text_cleanup(m);
553     } else
554         text_to_ass(&buf, ptr, end, avctx);
555 
556     ret = ff_ass_add_rect(sub, buf.str, m->readorder++, 0, NULL, NULL);
557     av_bprint_finalize(&buf, NULL);
558     if (ret < 0)
559         return ret;
560     *got_sub_ptr = sub->num_rects > 0;
561     return avpkt->size;
562 }
563 
mov_text_decode_close(AVCodecContext *avctx)564 static int mov_text_decode_close(AVCodecContext *avctx)
565 {
566     MovTextContext *m = avctx->priv_data;
567     mov_text_cleanup_ftab(m);
568     mov_text_cleanup(m);
569     return 0;
570 }
571 
mov_text_flush(AVCodecContext *avctx)572 static void mov_text_flush(AVCodecContext *avctx)
573 {
574     MovTextContext *m = avctx->priv_data;
575     if (!(avctx->flags2 & AV_CODEC_FLAG2_RO_FLUSH_NOOP))
576         m->readorder = 0;
577 }
578 
579 #define OFFSET(x) offsetof(MovTextContext, x)
580 #define FLAGS AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_SUBTITLE_PARAM
581 static const AVOption options[] = {
582     { "width", "Frame width, usually video width", OFFSET(frame_width), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
583     { "height", "Frame height, usually video height", OFFSET(frame_height), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
584     { NULL },
585 };
586 
587 static const AVClass mov_text_decoder_class = {
588     .class_name = "MOV text decoder",
589     .item_name  = av_default_item_name,
590     .option     = options,
591     .version    = LIBAVUTIL_VERSION_INT,
592 };
593 
594 const FFCodec ff_movtext_decoder = {
595     .p.name       = "mov_text",
596     .p.long_name  = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
597     .p.type       = AVMEDIA_TYPE_SUBTITLE,
598     .p.id         = AV_CODEC_ID_MOV_TEXT,
599     .priv_data_size = sizeof(MovTextContext),
600     .p.priv_class = &mov_text_decoder_class,
601     .init         = mov_text_init,
602     FF_CODEC_DECODE_SUB_CB(mov_text_decode_frame),
603     .close        = mov_text_decode_close,
604     .flush        = mov_text_flush,
605     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
606 };
607