libavcodec/pgssubdec.c

   1 /*
   2  * PGS subtitle decoder
   3  * Copyright (c) 2009 Stephen Backway
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * PGS subtitle decoder
  25  */
  26
  27 #include "avcodec.h"
  28 #include "bytestream.h"
  29 #include "internal.h"
  30 #include "mathops.h"
  31
  32 #include "libavutil/colorspace.h"
  33 #include "libavutil/imgutils.h"
  34
  35 #define RGBA(r,g,b,a) (((a) << 24) | ((r) << 16) | ((g) << 8) | (b))
  36 #define MAX_EPOCH_PALETTES 8   // Max 8 allowed per PGS epoch
  37 #define MAX_EPOCH_OBJECTS  64  // Max 64 allowed per PGS epoch
  38 #define MAX_OBJECT_REFS    2   // Max objects per display set
  39
  40 enum SegmentType {
  41     PALETTE_SEGMENT      = 0x14,
  42     OBJECT_SEGMENT       = 0x15,
  43     PRESENTATION_SEGMENT = 0x16,
  44     WINDOW_SEGMENT       = 0x17,
  45     DISPLAY_SEGMENT      = 0x80,
  46 };
  47
  48 typedef struct PGSSubObjectRef {
  49     int     id;
  50     int     window_id;
  51     uint8_t composition_flag;
  52     int     x;
  53     int     y;
  54     int     crop_x;
  55     int     crop_y;
  56     int     crop_w;
  57     int     crop_h;
  58 } PGSSubObjectRef;
  59
  60 typedef struct PGSSubPresentation {
  61     int id_number;
  62     int palette_id;
  63     int object_count;
  64     PGSSubObjectRef objects[MAX_OBJECT_REFS];
  65     int64_t pts;
  66 } PGSSubPresentation;
  67
  68 typedef struct PGSSubObject {
  69     int          id;
  70     int          w;
  71     int          h;
  72     uint8_t      *rle;
  73     unsigned int rle_buffer_size, rle_data_len;
  74     unsigned int rle_remaining_len;
  75 } PGSSubObject;
  76
  77 typedef struct PGSSubObjects {
  78     int          count;
  79     PGSSubObject object[MAX_EPOCH_OBJECTS];
  80 } PGSSubObjects;
  81
  82 typedef struct PGSSubPalette {
  83     int         id;
  84     uint32_t    clut[256];
  85 } PGSSubPalette;
  86
  87 typedef struct PGSSubPalettes {
  88     int           count;
  89     PGSSubPalette palette[MAX_EPOCH_PALETTES];
  90 } PGSSubPalettes;
  91
  92 typedef struct PGSSubContext {
  93     PGSSubPresentation presentation;
  94     PGSSubPalettes     palettes;
  95     PGSSubObjects      objects;
  96 } PGSSubContext;
  97
  98 static void flush_cache(AVCodecContext *avctx)
  99 {
 100     PGSSubContext *ctx = avctx->priv_data;
 101     int i;
 102
 103     for (i = 0; i < ctx->objects.count; i++) {
 104         av_freep(&ctx->objects.object[i].rle);
 105         ctx->objects.object[i].rle_buffer_size  = 0;
 106         ctx->objects.object[i].rle_remaining_len  = 0;
 107     }
 108     ctx->objects.count = 0;
 109     ctx->palettes.count = 0;
 110 }
 111
 112 static PGSSubObject * find_object(int id, PGSSubObjects *objects)
 113 {
 114     int i;
 115
 116     for (i = 0; i < objects->count; i++) {
 117         if (objects->object[i].id == id)
 118             return &objects->object[i];
 119     }
 120     return NULL;
 121 }
 122
 123 static PGSSubPalette * find_palette(int id, PGSSubPalettes *palettes)
 124 {
 125     int i;
 126
 127     for (i = 0; i < palettes->count; i++) {
 128         if (palettes->palette[i].id == id)
 129             return &palettes->palette[i];
 130     }
 131     return NULL;
 132 }
 133
 134 static av_cold int init_decoder(AVCodecContext *avctx)
 135 {
 136     avctx->pix_fmt = AV_PIX_FMT_PAL8;
 137
 138     return 0;
 139 }
 140
 141 static av_cold int close_decoder(AVCodecContext *avctx)
 142 {
 143     flush_cache(avctx);
 144
 145     return 0;
 146 }
 147
 148 /**
 149  * Decode the RLE data.
 150  *
 151  * The subtitle is stored as an Run Length Encoded image.
 152  *
 153  * @param avctx contains the current codec context
 154  * @param sub pointer to the processed subtitle data
 155  * @param buf pointer to the RLE data to process
 156  * @param buf_size size of the RLE data to process
 157  */
 158 static int decode_rle(AVCodecContext *avctx, AVSubtitleRect *rect,
 159                       const uint8_t *buf, unsigned int buf_size)
 160 {
 161     const uint8_t *rle_bitmap_end;
 162     int pixel_count, line_count;
 163
 164     rle_bitmap_end = buf + buf_size;
 165
 166     rect->data[0] = av_malloc(rect->w * rect->h);
 167
 168     if (!rect->data[0])
 169         return AVERROR(ENOMEM);
 170
 171     pixel_count = 0;
 172     line_count  = 0;
 173
 174     while (buf < rle_bitmap_end && line_count < rect->h) {
 175         uint8_t flags, color;
 176         int run;
 177
 178         color = bytestream_get_byte(&buf);
 179         run   = 1;
 180
 181         if (color == 0x00) {
 182             flags = bytestream_get_byte(&buf);
 183             run   = flags & 0x3f;
 184             if (flags & 0x40)
 185                 run = (run << 8) + bytestream_get_byte(&buf);
 186             color = flags & 0x80 ? bytestream_get_byte(&buf) : 0;
 187         }
 188
 189         if (run > 0 && pixel_count + run <= rect->w * rect->h) {
 190             memset(rect->data[0] + pixel_count, color, run);
 191             pixel_count += run;
 192         } else if (!run) {
 193             /*
 194              * New Line. Check if correct pixels decoded, if not display warning
 195              * and adjust bitmap pointer to correct new line position.
 196              */
 197             if (pixel_count % rect->w > 0) {
 198                 av_log(avctx, AV_LOG_ERROR, "Decoded %d pixels, when line should be %d pixels\n",
 199                        pixel_count % rect->w, rect->w);
 200                 if (avctx->err_recognition & AV_EF_EXPLODE) {
 201                     return AVERROR_INVALIDDATA;
 202                 }
 203             }
 204             line_count++;
 205         }
 206     }
 207
 208     if (pixel_count < rect->w * rect->h) {
 209         av_log(avctx, AV_LOG_ERROR, "Insufficient RLE data for subtitle\n");
 210         return AVERROR_INVALIDDATA;
 211     }
 212
 213     ff_dlog(avctx, "Pixel Count = %d, Area = %d\n", pixel_count, rect->w * rect->h);
 214
 215     return 0;
 216 }
 217
 218 /**
 219  * Parse the picture segment packet.
 220  *
 221  * The picture segment contains details on the sequence id,
 222  * width, height and Run Length Encoded (RLE) bitmap data.
 223  *
 224  * @param avctx contains the current codec context
 225  * @param buf pointer to the packet to process
 226  * @param buf_size size of packet to process
 227  */
 228 static int parse_object_segment(AVCodecContext *avctx,
 229                                   const uint8_t *buf, int buf_size)
 230 {
 231     PGSSubContext *ctx = avctx->priv_data;
 232     PGSSubObject *object;
 233
 234     uint8_t sequence_desc;
 235     unsigned int rle_bitmap_len, width, height;
 236     int id;
 237
 238     if (buf_size <= 4)
 239         return AVERROR_INVALIDDATA;
 240     buf_size -= 4;
 241
 242     id = bytestream_get_be16(&buf);
 243     object = find_object(id, &ctx->objects);
 244     if (!object) {
 245         if (ctx->objects.count >= MAX_EPOCH_OBJECTS) {
 246             av_log(avctx, AV_LOG_ERROR, "Too many objects in epoch\n");
 247             return AVERROR_INVALIDDATA;
 248         }
 249         object = &ctx->objects.object[ctx->objects.count++];
 250         object->id = id;
 251     }
 252
 253     /* skip object version number */
 254     buf += 1;
 255
 256     /* Read the Sequence Description to determine if start of RLE data or appended to previous RLE */
 257     sequence_desc = bytestream_get_byte(&buf);
 258
 259     if (!(sequence_desc & 0x80)) {
 260         /* Additional RLE data */
 261         if (buf_size > object->rle_remaining_len)
 262             return AVERROR_INVALIDDATA;
 263
 264         memcpy(object->rle + object->rle_data_len, buf, buf_size);
 265         object->rle_data_len += buf_size;
 266         object->rle_remaining_len -= buf_size;
 267
 268         return 0;
 269     }
 270
 271     if (buf_size <= 7)
 272         return AVERROR_INVALIDDATA;
 273     buf_size -= 7;
 274
 275     /* Decode rle bitmap length, stored size includes width/height data */
 276     rle_bitmap_len = bytestream_get_be24(&buf) - 2*2;
 277
 278     if (buf_size > rle_bitmap_len) {
 279         av_log(avctx, AV_LOG_ERROR,
 280                "Buffer dimension %d larger than the expected RLE data %d\n",
 281                buf_size, rle_bitmap_len);
 282         return AVERROR_INVALIDDATA;
 283     }
 284
 285     /* Get bitmap dimensions from data */
 286     width  = bytestream_get_be16(&buf);
 287     height = bytestream_get_be16(&buf);
 288
 289     /* Make sure the bitmap is not too large */
 290     if (avctx->width < width || avctx->height < height) {
 291         av_log(avctx, AV_LOG_ERROR, "Bitmap dimensions larger than video.\n");
 292         return AVERROR_INVALIDDATA;
 293     }
 294
 295     object->w = width;
 296     object->h = height;
 297
 298     av_fast_malloc(&object->rle, &object->rle_buffer_size, rle_bitmap_len);
 299
 300     if (!object->rle)
 301         return AVERROR(ENOMEM);
 302
 303     memcpy(object->rle, buf, buf_size);
 304     object->rle_data_len = buf_size;
 305     object->rle_remaining_len = rle_bitmap_len - buf_size;
 306
 307     return 0;
 308 }
 309
 310 /**
 311  * Parse the palette segment packet.
 312  *
 313  * The palette segment contains details of the palette,
 314  * a maximum of 256 colors can be defined.
 315  *
 316  * @param avctx contains the current codec context
 317  * @param buf pointer to the packet to process
 318  * @param buf_size size of packet to process
 319  */
 320 static int parse_palette_segment(AVCodecContext *avctx,
 321                                   const uint8_t *buf, int buf_size)
 322 {
 323     PGSSubContext *ctx = avctx->priv_data;
 324     PGSSubPalette *palette;
 325
 326     const uint8_t *buf_end = buf + buf_size;
 327     const uint8_t *cm      = ff_crop_tab + MAX_NEG_CROP;
 328     int color_id;
 329     int y, cb, cr, alpha;
 330     int r, g, b, r_add, g_add, b_add;
 331     int id;
 332
 333     id  = bytestream_get_byte(&buf);
 334     palette = find_palette(id, &ctx->palettes);
 335     if (!palette) {
 336         if (ctx->palettes.count >= MAX_EPOCH_PALETTES) {
 337             av_log(avctx, AV_LOG_ERROR, "Too many palettes in epoch\n");
 338             return AVERROR_INVALIDDATA;
 339         }
 340         palette = &ctx->palettes.palette[ctx->palettes.count++];
 341         palette->id  = id;
 342     }
 343
 344     /* Skip palette version */
 345     buf += 1;
 346
 347     while (buf < buf_end) {
 348         color_id  = bytestream_get_byte(&buf);
 349         y         = bytestream_get_byte(&buf);
 350         cr        = bytestream_get_byte(&buf);
 351         cb        = bytestream_get_byte(&buf);
 352         alpha     = bytestream_get_byte(&buf);
 353
 354         YUV_TO_RGB1(cb, cr);
 355         YUV_TO_RGB2(r, g, b, y);
 356
 357         ff_dlog(avctx, "Color %d := (%d,%d,%d,%d)\n", color_id, r, g, b, alpha);
 358
 359         /* Store color in palette */
 360         palette->clut[color_id] = RGBA(r,g,b,alpha);
 361     }
 362     return 0;
 363 }
 364
 365 /**
 366  * Parse the presentation segment packet.
 367  *
 368  * The presentation segment contains details on the video
 369  * width, video height, x & y subtitle position.
 370  *
 371  * @param avctx contains the current codec context
 372  * @param buf pointer to the packet to process
 373  * @param buf_size size of packet to process
 374  * @todo TODO: Implement cropping
 375  */
 376 static int parse_presentation_segment(AVCodecContext *avctx,
 377                                       const uint8_t *buf, int buf_size,
 378                                       int64_t pts)
 379 {
 380     PGSSubContext *ctx = avctx->priv_data;
 381
 382     int i, state, ret;
 383
 384     // Video descriptor
 385     int w = bytestream_get_be16(&buf);
 386     int h = bytestream_get_be16(&buf);
 387
 388     ctx->presentation.pts = pts;
 389
 390     ff_dlog(avctx, "Video Dimensions %dx%d\n",
 391             w, h);
 392     ret = ff_set_dimensions(avctx, w, h);
 393     if (ret < 0)
 394         return ret;
 395
 396     /* Skip 1 bytes of unknown, frame rate */
 397     buf++;
 398
 399     // Composition descriptor
 400     ctx->presentation.id_number = bytestream_get_be16(&buf);
 401     /*
 402      * state is a 2 bit field that defines pgs epoch boundaries
 403      * 00 - Normal, previously defined objects and palettes are still valid
 404      * 01 - Acquisition point, previous objects and palettes can be released
 405      * 10 - Epoch start, previous objects and palettes can be released
 406      * 11 - Epoch continue, previous objects and palettes can be released
 407      *
 408      * reserved 6 bits discarded
 409      */
 410     state = bytestream_get_byte(&buf) >> 6;
 411     if (state != 0) {
 412         flush_cache(avctx);
 413     }
 414
 415     /*
 416      * skip palette_update_flag (0x80),
 417      */
 418     buf += 1;
 419     ctx->presentation.palette_id = bytestream_get_byte(&buf);
 420     ctx->presentation.object_count = bytestream_get_byte(&buf);
 421     if (ctx->presentation.object_count > MAX_OBJECT_REFS) {
 422         av_log(avctx, AV_LOG_ERROR,
 423                "Invalid number of presentation objects %d\n",
 424                ctx->presentation.object_count);
 425         ctx->presentation.object_count = 2;
 426         if (avctx->err_recognition & AV_EF_EXPLODE) {
 427             return AVERROR_INVALIDDATA;
 428         }
 429     }
 430
 431     for (i = 0; i < ctx->presentation.object_count; i++)
 432     {
 433         ctx->presentation.objects[i].id = bytestream_get_be16(&buf);
 434         ctx->presentation.objects[i].window_id = bytestream_get_byte(&buf);
 435         ctx->presentation.objects[i].composition_flag = bytestream_get_byte(&buf);
 436
 437         ctx->presentation.objects[i].x = bytestream_get_be16(&buf);
 438         ctx->presentation.objects[i].y = bytestream_get_be16(&buf);
 439
 440         // If cropping
 441         if (ctx->presentation.objects[i].composition_flag & 0x80) {
 442             ctx->presentation.objects[i].crop_x = bytestream_get_be16(&buf);
 443             ctx->presentation.objects[i].crop_y = bytestream_get_be16(&buf);
 444             ctx->presentation.objects[i].crop_w = bytestream_get_be16(&buf);
 445             ctx->presentation.objects[i].crop_h = bytestream_get_be16(&buf);
 446         }
 447
 448         ff_dlog(avctx, "Subtitle Placement x=%d, y=%d\n",
 449                 ctx->presentation.objects[i].x, ctx->presentation.objects[i].y);
 450
 451         if (ctx->presentation.objects[i].x > avctx->width ||
 452             ctx->presentation.objects[i].y > avctx->height) {
 453             av_log(avctx, AV_LOG_ERROR, "Subtitle out of video bounds. x = %d, y = %d, video width = %d, video height = %d.\n",
 454                    ctx->presentation.objects[i].x,
 455                    ctx->presentation.objects[i].y,
 456                     avctx->width, avctx->height);
 457             ctx->presentation.objects[i].x = 0;
 458             ctx->presentation.objects[i].y = 0;
 459             if (avctx->err_recognition & AV_EF_EXPLODE) {
 460                 return AVERROR_INVALIDDATA;
 461             }
 462         }
 463     }
 464
 465     return 0;
 466 }
 467
 468 /**
 469  * Parse the display segment packet.
 470  *
 471  * The display segment controls the updating of the display.
 472  *
 473  * @param avctx contains the current codec context
 474  * @param data pointer to the data pertaining the subtitle to display
 475  * @param buf pointer to the packet to process
 476  * @param buf_size size of packet to process
 477  */
 478 static int display_end_segment(AVCodecContext *avctx, void *data,
 479                                const uint8_t *buf, int buf_size)
 480 {
 481     AVSubtitle    *sub = data;
 482     PGSSubContext *ctx = avctx->priv_data;
 483     PGSSubPalette *palette;
 484     int i, ret;
 485
 486     memset(sub, 0, sizeof(*sub));
 487     sub->pts = ctx->presentation.pts;
 488     sub->start_display_time = 0;
 489     // There is no explicit end time for PGS subtitles.  The end time
 490     // is defined by the start of the next sub which may contain no
 491     // objects (i.e. clears the previous sub)
 492     sub->end_display_time   = UINT32_MAX;
 493     sub->format             = 0;
 494
 495     // Blank if last object_count was 0.
 496     if (!ctx->presentation.object_count)
 497         return 1;
 498     sub->rects = av_mallocz(sizeof(*sub->rects) * ctx->presentation.object_count);
 499     if (!sub->rects) {
 500         return AVERROR(ENOMEM);
 501     }
 502     palette = find_palette(ctx->presentation.palette_id, &ctx->palettes);
 503     if (!palette) {
 504         // Missing palette.  Should only happen with damaged streams.
 505         av_log(avctx, AV_LOG_ERROR, "Invalid palette id %d\n",
 506                ctx->presentation.palette_id);
 507         avsubtitle_free(sub);
 508         return AVERROR_INVALIDDATA;
 509     }
 510     for (i = 0; i < ctx->presentation.object_count; i++) {
 511         PGSSubObject *object;
 512         AVSubtitleRect *rect;
 513         int j;
 514
 515         sub->rects[i]  = av_mallocz(sizeof(*sub->rects[0]));
 516         if (!sub->rects[i]) {
 517             avsubtitle_free(sub);
 518             return AVERROR(ENOMEM);
 519         }
 520         sub->num_rects++;
 521         sub->rects[i]->type = SUBTITLE_BITMAP;
 522
 523         /* Process bitmap */
 524         object = find_object(ctx->presentation.objects[i].id, &ctx->objects);
 525         if (!object) {
 526             // Missing object.  Should only happen with damaged streams.
 527             av_log(avctx, AV_LOG_ERROR, "Invalid object id %d\n",
 528                    ctx->presentation.objects[i].id);
 529             if (avctx->err_recognition & AV_EF_EXPLODE) {
 530                 avsubtitle_free(sub);
 531                 return AVERROR_INVALIDDATA;
 532             }
 533             // Leaves rect empty with 0 width and height.
 534             continue;
 535         }
 536         if (ctx->presentation.objects[i].composition_flag & 0x40)
 537             sub->rects[i]->flags |= AV_SUBTITLE_FLAG_FORCED;
 538
 539         sub->rects[i]->x    = ctx->presentation.objects[i].x;
 540         sub->rects[i]->y    = ctx->presentation.objects[i].y;
 541         sub->rects[i]->w    = object->w;
 542         sub->rects[i]->h    = object->h;
 543
 544         sub->rects[i]->linesize[0] = object->w;
 545
 546         if (object->rle) {
 547             if (object->rle_remaining_len) {
 548                 av_log(avctx, AV_LOG_ERROR, "RLE data length %u is %u bytes shorter than expected\n",
 549                        object->rle_data_len, object->rle_remaining_len);
 550                 if (avctx->err_recognition & AV_EF_EXPLODE) {
 551                     avsubtitle_free(sub);
 552                     return AVERROR_INVALIDDATA;
 553                 }
 554             }
 555             ret = decode_rle(avctx, sub->rects[i], object->rle, object->rle_data_len);
 556             if (ret < 0) {
 557                 if ((avctx->err_recognition & AV_EF_EXPLODE) ||
 558                     ret == AVERROR(ENOMEM)) {
 559                     avsubtitle_free(sub);
 560                     return ret;
 561                 }
 562                 sub->rects[i]->w = 0;
 563                 sub->rects[i]->h = 0;
 564                 continue;
 565             }
 566         }
 567         /* Allocate memory for colors */
 568         sub->rects[i]->nb_colors    = 256;
 569         sub->rects[i]->data[1] = av_mallocz(AVPALETTE_SIZE);
 570         if (!sub->rects[i]->data[1]) {
 571             avsubtitle_free(sub);
 572             return AVERROR(ENOMEM);
 573         }
 574
 575 #if FF_API_AVPICTURE
 576 FF_DISABLE_DEPRECATION_WARNINGS
 577         rect = sub->rects[i];
 578         for (j = 0; j < 4; j++) {
 579             rect->pict.data[j] = rect->data[j];
 580             rect->pict.linesize[j] = rect->linesize[j];
 581         }
 582 FF_ENABLE_DEPRECATION_WARNINGS
 583 #endif
 584
 585         memcpy(sub->rects[i]->data[1], palette->clut, sub->rects[i]->nb_colors * sizeof(uint32_t));
 586
 587     }
 588     return 1;
 589 }
 590
 591 static int decode(AVCodecContext *avctx, void *data, int *data_size,
 592                   AVPacket *avpkt)
 593 {
 594     const uint8_t *buf = avpkt->data;
 595     int buf_size       = avpkt->size;
 596
 597     const uint8_t *buf_end;
 598     uint8_t       segment_type;
 599     int           segment_length;
 600     int i, ret;
 601
 602     ff_dlog(avctx, "PGS sub packet:\n");
 603
 604     for (i = 0; i < buf_size; i++) {
 605         ff_dlog(avctx, "%02x ", buf[i]);
 606         if (i % 16 == 15)
 607             ff_dlog(avctx, "\n");
 608     }
 609
 610     if (i & 15)
 611         ff_dlog(avctx, "\n");
 612
 613     *data_size = 0;
 614
 615     /* Ensure that we have received at a least a segment code and segment length */
 616     if (buf_size < 3)
 617         return -1;
 618
 619     buf_end = buf + buf_size;
 620
 621     /* Step through buffer to identify segments */
 622     while (buf < buf_end) {
 623         segment_type   = bytestream_get_byte(&buf);
 624         segment_length = bytestream_get_be16(&buf);
 625
 626         ff_dlog(avctx, "Segment Length %d, Segment Type %x\n", segment_length, segment_type);
 627
 628         if (segment_type != DISPLAY_SEGMENT && segment_length > buf_end - buf)
 629             break;
 630
 631         ret = 0;
 632         switch (segment_type) {
 633         case PALETTE_SEGMENT:
 634             ret = parse_palette_segment(avctx, buf, segment_length);
 635             break;
 636         case OBJECT_SEGMENT:
 637             ret = parse_object_segment(avctx, buf, segment_length);
 638             break;
 639         case PRESENTATION_SEGMENT:
 640             ret = parse_presentation_segment(avctx, buf, segment_length, avpkt->pts);
 641             break;
 642         case WINDOW_SEGMENT:
 643             /*
 644              * Window Segment Structure (No new information provided):
 645              *     2 bytes: Unknown,
 646              *     2 bytes: X position of subtitle,
 647              *     2 bytes: Y position of subtitle,
 648              *     2 bytes: Width of subtitle,
 649              *     2 bytes: Height of subtitle.
 650              */
 651             break;
 652         case DISPLAY_SEGMENT:
 653             ret = display_end_segment(avctx, data, buf, segment_length);
 654             if (ret >= 0)
 655                 *data_size = ret;
 656             break;
 657         default:
 658             av_log(avctx, AV_LOG_ERROR, "Unknown subtitle segment type 0x%x, length %d\n",
 659                    segment_type, segment_length);
 660             ret = AVERROR_INVALIDDATA;
 661             break;
 662         }
 663         if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
 664             return ret;
 665
 666         buf += segment_length;
 667     }
 668
 669     return buf_size;
 670 }
 671
 672 AVCodec ff_pgssub_decoder = {
 673     .name           = "pgssub",
 674     .long_name      = NULL_IF_CONFIG_SMALL("HDMV Presentation Graphic Stream subtitles"),
 675     .type           = AVMEDIA_TYPE_SUBTITLE,
 676     .id             = AV_CODEC_ID_HDMV_PGS_SUBTITLE,
 677     .priv_data_size = sizeof(PGSSubContext),
 678     .init           = init_decoder,
 679     .close          = close_decoder,
 680     .decode         = decode,
 681 };