libavcodec/ccaption_dec.c - nest-android-app/ffmpeg - Git at Google

 /*
  * Closed Caption Decoding
  * Copyright (c) 2015 Anshul Maheshwari
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 #include "avcodec.h"
 #include "ass.h"
 #include "libavutil/opt.h"

 #define SCREEN_ROWS 15
 #define SCREEN_COLUMNS 32

 #define SET_FLAG(var, val)   ( (var) |=   ( 1 << (val)) )
 #define UNSET_FLAG(var, val) ( (var) &=  ~( 1 << (val)) )
 #define CHECK_FLAG(var, val) ( (var) &    ( 1 << (val)) )

 static const AVRational ass_tb = {1, 100};

 /*
  * TODO list
  * 1) handle font and color completely
  */
 enum cc_mode {
     CCMODE_POPON,
     CCMODE_PAINTON,
     CCMODE_ROLLUP,
     CCMODE_TEXT,
 };

 enum cc_color_code {
     CCCOL_WHITE,
     CCCOL_GREEN,
     CCCOL_BLUE,
     CCCOL_CYAN,
     CCCOL_RED,
     CCCOL_YELLOW,
     CCCOL_MAGENTA,
     CCCOL_USERDEFINED,
     CCCOL_BLACK,
     CCCOL_TRANSPARENT,
 };

 enum cc_font {
     CCFONT_REGULAR,
     CCFONT_ITALICS,
     CCFONT_UNDERLINED,
     CCFONT_UNDERLINED_ITALICS,
 };

 static const unsigned char pac2_attribs[32][3] = // Color, font, ident
 {
     { CCCOL_WHITE,   CCFONT_REGULAR,            0 },  // 0x40 || 0x60
     { CCCOL_WHITE,   CCFONT_UNDERLINED,         0 },  // 0x41 || 0x61
     { CCCOL_GREEN,   CCFONT_REGULAR,            0 },  // 0x42 || 0x62
     { CCCOL_GREEN,   CCFONT_UNDERLINED,         0 },  // 0x43 || 0x63
     { CCCOL_BLUE,    CCFONT_REGULAR,            0 },  // 0x44 || 0x64
     { CCCOL_BLUE,    CCFONT_UNDERLINED,         0 },  // 0x45 || 0x65
     { CCCOL_CYAN,    CCFONT_REGULAR,            0 },  // 0x46 || 0x66
     { CCCOL_CYAN,    CCFONT_UNDERLINED,         0 },  // 0x47 || 0x67
     { CCCOL_RED,     CCFONT_REGULAR,            0 },  // 0x48 || 0x68
     { CCCOL_RED,     CCFONT_UNDERLINED,         0 },  // 0x49 || 0x69
     { CCCOL_YELLOW,  CCFONT_REGULAR,            0 },  // 0x4a || 0x6a
     { CCCOL_YELLOW,  CCFONT_UNDERLINED,         0 },  // 0x4b || 0x6b
     { CCCOL_MAGENTA, CCFONT_REGULAR,            0 },  // 0x4c || 0x6c
     { CCCOL_MAGENTA, CCFONT_UNDERLINED,         0 },  // 0x4d || 0x6d
     { CCCOL_WHITE,   CCFONT_ITALICS,            0 },  // 0x4e || 0x6e
     { CCCOL_WHITE,   CCFONT_UNDERLINED_ITALICS, 0 },  // 0x4f || 0x6f
     { CCCOL_WHITE,   CCFONT_REGULAR,            0 },  // 0x50 || 0x70
     { CCCOL_WHITE,   CCFONT_UNDERLINED,         0 },  // 0x51 || 0x71
     { CCCOL_WHITE,   CCFONT_REGULAR,            4 },  // 0x52 || 0x72
     { CCCOL_WHITE,   CCFONT_UNDERLINED,         4 },  // 0x53 || 0x73
     { CCCOL_WHITE,   CCFONT_REGULAR,            8 },  // 0x54 || 0x74
     { CCCOL_WHITE,   CCFONT_UNDERLINED,         8 },  // 0x55 || 0x75
     { CCCOL_WHITE,   CCFONT_REGULAR,           12 },  // 0x56 || 0x76
     { CCCOL_WHITE,   CCFONT_UNDERLINED,        12 },  // 0x57 || 0x77
     { CCCOL_WHITE,   CCFONT_REGULAR,           16 },  // 0x58 || 0x78
     { CCCOL_WHITE,   CCFONT_UNDERLINED,        16 },  // 0x59 || 0x79
     { CCCOL_WHITE,   CCFONT_REGULAR,           20 },  // 0x5a || 0x7a
     { CCCOL_WHITE,   CCFONT_UNDERLINED,        20 },  // 0x5b || 0x7b
     { CCCOL_WHITE,   CCFONT_REGULAR,           24 },  // 0x5c || 0x7c
     { CCCOL_WHITE,   CCFONT_UNDERLINED,        24 },  // 0x5d || 0x7d
     { CCCOL_WHITE,   CCFONT_REGULAR,           28 },  // 0x5e || 0x7e
     { CCCOL_WHITE,   CCFONT_UNDERLINED,        28 }   // 0x5f || 0x7f
     /* total 32 entries */
 };

 struct Screen {
     /* +1 is used to compensate null character of string */
     uint8_t characters[SCREEN_ROWS][SCREEN_COLUMNS+1];
     uint8_t colors[SCREEN_ROWS][SCREEN_COLUMNS+1];
     uint8_t fonts[SCREEN_ROWS][SCREEN_COLUMNS+1];
     /*
      * Bitmask of used rows; if a bit is not set, the
      * corresponding row is not used.
      * for setting row 1  use row | (1 << 0)
      * for setting row 15 use row | (1 << 14)
      */
     int16_t row_used;
 };

 typedef struct CCaptionSubContext {
     AVClass *class;
     int real_time;
     struct Screen screen[2];
     int active_screen;
     uint8_t cursor_row;
     uint8_t cursor_column;
     uint8_t cursor_color;
     uint8_t cursor_font;
     AVBPrint buffer;
     int buffer_changed;
     int rollup;
     enum cc_mode mode;
     int64_t start_time;
     /* visible screen time */
     int64_t startv_time;
     int64_t end_time;
     int screen_touched;
     int64_t last_real_time;
     char prev_cmd[2];
     /* buffer to store pkt data */
     AVBufferRef *pktbuf;
 } CCaptionSubContext;


 static av_cold int init_decoder(AVCodecContext *avctx)
 {
     int ret;
     CCaptionSubContext *ctx = avctx->priv_data;

     av_bprint_init(&ctx->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
     /* taking by default roll up to 2 */
     ctx->mode = CCMODE_ROLLUP;
     ctx->rollup = 2;
     ret = ff_ass_subtitle_header(avctx, "Monospace",
                                  ASS_DEFAULT_FONT_SIZE,
                                  ASS_DEFAULT_COLOR,
                                  ASS_DEFAULT_BACK_COLOR,
                                  ASS_DEFAULT_BOLD,
                                  ASS_DEFAULT_ITALIC,
                                  ASS_DEFAULT_UNDERLINE,
                                  3,
                                  ASS_DEFAULT_ALIGNMENT);
     if (ret < 0) {
         return ret;
     }
     /* allocate pkt buffer */
     ctx->pktbuf = av_buffer_alloc(128);
     if (!ctx->pktbuf) {
         ret = AVERROR(ENOMEM);
     }
     return ret;
 }

 static av_cold int close_decoder(AVCodecContext *avctx)
 {
     CCaptionSubContext *ctx = avctx->priv_data;
     av_bprint_finalize(&ctx->buffer, NULL);
     av_buffer_unref(&ctx->pktbuf);
     return 0;
 }

 static void flush_decoder(AVCodecContext *avctx)
 {
     CCaptionSubContext *ctx = avctx->priv_data;
     ctx->screen[0].row_used = 0;
     ctx->screen[1].row_used = 0;
     ctx->prev_cmd[0] = 0;
     ctx->prev_cmd[1] = 0;
     ctx->mode = CCMODE_ROLLUP;
     ctx->rollup = 2;
     ctx->cursor_row = 0;
     ctx->cursor_column = 0;
     ctx->cursor_font = 0;
     ctx->cursor_color = 0;
     ctx->active_screen = 0;
     ctx->last_real_time = 0;
     ctx->screen_touched = 0;
     ctx->buffer_changed = 0;
     av_bprint_clear(&ctx->buffer);
 }

 /**
  * @param ctx closed caption context just to print log
  */
 static int write_char(CCaptionSubContext *ctx, struct Screen *screen, char ch)
 {
     uint8_t col = ctx->cursor_column;
     char *row = screen->characters[ctx->cursor_row];
     char *font = screen->fonts[ctx->cursor_row];

     if (col < SCREEN_COLUMNS) {
         row[col] = ch;
         font[col] = ctx->cursor_font;
         if (ch) ctx->cursor_column++;
         return 0;
     }
     /* We have extra space at end only for null character */
     else if (col == SCREEN_COLUMNS && ch == 0) {
         row[col] = ch;
         return 0;
     }
     else {
         av_log(ctx, AV_LOG_WARNING, "Data Ignored since exceeding screen width\n");
         return AVERROR_INVALIDDATA;
     }
 }

 /**
  * This function after validating parity bit, also remove it from data pair.
  * The first byte doesn't pass parity, we replace it with a solid blank
  * and process the pair.
  * If the second byte doesn't pass parity, it returns INVALIDDATA
  * user can ignore the whole pair and pass the other pair.
  */
 static int validate_cc_data_pair(uint8_t *cc_data_pair)
 {
     uint8_t cc_valid = (*cc_data_pair & 4) >>2;
     uint8_t cc_type = *cc_data_pair & 3;

     if (!cc_valid)
         return AVERROR_INVALIDDATA;

     // if EIA-608 data then verify parity.
     if (cc_type==0 || cc_type==1) {
         if (!av_parity(cc_data_pair[2])) {
             return AVERROR_INVALIDDATA;
         }
         if (!av_parity(cc_data_pair[1])) {
             cc_data_pair[1]=0x7F;
         }
     }

     //Skip non-data
     if ((cc_data_pair[0] == 0xFA || cc_data_pair[0] == 0xFC || cc_data_pair[0] == 0xFD)
          && (cc_data_pair[1] & 0x7F) == 0 && (cc_data_pair[2] & 0x7F) == 0)
         return AVERROR_PATCHWELCOME;

     //skip 708 data
     if (cc_type == 3 || cc_type == 2)
         return AVERROR_PATCHWELCOME;

     /* remove parity bit */
     cc_data_pair[1] &= 0x7F;
     cc_data_pair[2] &= 0x7F;

     return 0;
 }

 static struct Screen *get_writing_screen(CCaptionSubContext *ctx)
 {
     switch (ctx->mode) {
     case CCMODE_POPON:
         // use Inactive screen
         return ctx->screen + !ctx->active_screen;
     case CCMODE_PAINTON:
     case CCMODE_ROLLUP:
     case CCMODE_TEXT:
         // use active screen
         return ctx->screen + ctx->active_screen;
     }
     /* It was never an option */
     return NULL;
 }

 static void roll_up(CCaptionSubContext *ctx)
 {
     struct Screen *screen;
     int i, keep_lines;

     if (ctx->mode == CCMODE_TEXT)
         return;

     screen = get_writing_screen(ctx);

     /* +1 signify cursor_row starts from 0
      * Can't keep lines less then row cursor pos
      */
     keep_lines = FFMIN(ctx->cursor_row + 1, ctx->rollup);

     for (i = 0; i < SCREEN_ROWS; i++) {
         if (i > ctx->cursor_row - keep_lines && i <= ctx->cursor_row)
             continue;
         UNSET_FLAG(screen->row_used, i);
     }

     for (i = 0; i < keep_lines && screen->row_used; i++) {
         const int i_row = ctx->cursor_row - keep_lines + i + 1;

         memcpy(screen->characters[i_row], screen->characters[i_row+1], SCREEN_COLUMNS);
         memcpy(screen->colors[i_row], screen->colors[i_row+1], SCREEN_COLUMNS);
         memcpy(screen->fonts[i_row], screen->fonts[i_row+1], SCREEN_COLUMNS);
         if (CHECK_FLAG(screen->row_used, i_row + 1))
             SET_FLAG(screen->row_used, i_row);
     }

     UNSET_FLAG(screen->row_used, ctx->cursor_row);
 }

 static int capture_screen(CCaptionSubContext *ctx)
 {
     int i;
     struct Screen *screen = ctx->screen + ctx->active_screen;
     enum cc_font prev_font = CCFONT_REGULAR;
     av_bprint_clear(&ctx->buffer);

     for (i = 0; screen->row_used && i < SCREEN_ROWS; i++)
     {
         if (CHECK_FLAG(screen->row_used, i)) {
             const char *row = screen->characters[i];
             const char *font = screen->fonts[i];
             int j = 0;

             /* skip leading space */
             while (row[j] == ' ')
                 j++;

             for (; j < SCREEN_COLUMNS; j++) {
                 const char *e_tag = "", *s_tag = "";

                 if (row[j] == 0)
                     break;

                 if (prev_font != font[j]) {
                     switch (prev_font) {
                     case CCFONT_ITALICS:
                         e_tag = "{\\i0}";
                         break;
                     case CCFONT_UNDERLINED:
                         e_tag = "{\\u0}";
                         break;
                     case CCFONT_UNDERLINED_ITALICS:
                         e_tag = "{\\u0}{\\i0}";
                         break;
                     }
                     switch (font[j]) {
                     case CCFONT_ITALICS:
                         s_tag = "{\\i1}";
                         break;
                     case CCFONT_UNDERLINED:
                         s_tag = "{\\u1}";
                         break;
                     case CCFONT_UNDERLINED_ITALICS:
                         s_tag = "{\\u1}{\\i1}";
                         break;
                     }
                 }
                 prev_font = font[j];
                 av_bprintf(&ctx->buffer, "%s%s%c", e_tag, s_tag, row[j]);
             }
             av_bprintf(&ctx->buffer, "\\N");
         }
     }
     if (!av_bprint_is_complete(&ctx->buffer))
         return AVERROR(ENOMEM);
     if (screen->row_used && ctx->buffer.len >= 2) {
         ctx->buffer.len -= 2;
         ctx->buffer.str[ctx->buffer.len] = 0;
     }
     ctx->buffer_changed = 1;
     return 0;
 }

 static int reap_screen(CCaptionSubContext *ctx, int64_t pts)
 {
     ctx->start_time = ctx->startv_time;
     ctx->startv_time = pts;
     ctx->end_time = pts;
     return capture_screen(ctx);
 }

 static void handle_textattr(CCaptionSubContext *ctx, uint8_t hi, uint8_t lo)
 {
     int i = lo - 0x20;
     struct Screen *screen = get_writing_screen(ctx);

     if (i >= 32)
         return;

     ctx->cursor_color = pac2_attribs[i][0];
     ctx->cursor_font = pac2_attribs[i][1];

     SET_FLAG(screen->row_used, ctx->cursor_row);
     write_char(ctx, screen, ' ');
 }

 static void handle_pac(CCaptionSubContext *ctx, uint8_t hi, uint8_t lo)
 {
     static const int8_t row_map[] = {
         11, -1, 1, 2, 3, 4, 12, 13, 14, 15, 5, 6, 7, 8, 9, 10
     };
     const int index = ( (hi<<1) & 0x0e) | ( (lo>>5) & 0x01 );
     struct Screen *screen = get_writing_screen(ctx);
     int indent, i;

     if (row_map[index] <= 0) {
         av_log(ctx, AV_LOG_DEBUG, "Invalid pac index encountered\n");
         return;
     }

     lo &= 0x1f;

     ctx->cursor_row = row_map[index] - 1;
     ctx->cursor_color =  pac2_attribs[lo][0];
     ctx->cursor_font = pac2_attribs[lo][1];
     ctx->cursor_column = 0;
     indent = pac2_attribs[lo][2];
     for (i = 0; i < indent; i++) {
         write_char(ctx, screen, ' ');
     }
 }

 /**
  * @param pts it is required to set end time
  */
 static void handle_edm(CCaptionSubContext *ctx, int64_t pts)
 {
     struct Screen *screen = ctx->screen + ctx->active_screen;

     // In buffered mode, keep writing to screen until it is wiped.
     // Before wiping the display, capture contents to emit subtitle.
     if (!ctx->real_time)
         reap_screen(ctx, pts);

     screen->row_used = 0;

     // In realtime mode, emit an empty caption so the last one doesn't
     // stay on the screen.
     if (ctx->real_time)
         reap_screen(ctx, pts);
 }

 static void handle_eoc(CCaptionSubContext *ctx, int64_t pts)
 {
     // In buffered mode, we wait til the *next* EOC and
     // reap what was already on the screen since the last EOC.
     if (!ctx->real_time)
         handle_edm(ctx,pts);

     ctx->active_screen = !ctx->active_screen;
     ctx->cursor_column = 0;

     // In realtime mode, we display the buffered contents (after
     // flipping the buffer to active above) as soon as EOC arrives.
     if (ctx->real_time)
         reap_screen(ctx, pts);
 }

 static void handle_delete_end_of_row(CCaptionSubContext *ctx, char hi, char lo)
 {
     struct Screen *screen = get_writing_screen(ctx);
     write_char(ctx, screen, 0);
 }

 static void handle_char(CCaptionSubContext *ctx, char hi, char lo, int64_t pts)
 {
     struct Screen *screen = get_writing_screen(ctx);

     SET_FLAG(screen->row_used, ctx->cursor_row);

     write_char(ctx, screen, hi);

     if (lo) {
         write_char(ctx, screen, lo);
     }
     write_char(ctx, screen, 0);

     if (ctx->mode != CCMODE_POPON)
         ctx->screen_touched = 1;

     /* reset prev command since character can repeat */
     ctx->prev_cmd[0] = 0;
     ctx->prev_cmd[1] = 0;
     if (lo)
        ff_dlog(ctx, "(%c,%c)\n", hi, lo);
     else
        ff_dlog(ctx, "(%c)\n", hi);
 }

 static void process_cc608(CCaptionSubContext *ctx, int64_t pts, uint8_t hi, uint8_t lo)
 {
     if (hi == ctx->prev_cmd[0] && lo == ctx->prev_cmd[1]) {
         /* ignore redundant command */
     } else if ( (hi == 0x10 && (lo >= 0x40 && lo <= 0x5f)) ||
               ( (hi >= 0x11 && hi <= 0x17) && (lo >= 0x40 && lo <= 0x7f) ) ) {
         handle_pac(ctx, hi, lo);
     } else if ( ( hi == 0x11 && lo >= 0x20 && lo <= 0x2f ) ||
                 ( hi == 0x17 && lo >= 0x2e && lo <= 0x2f) ) {
         handle_textattr(ctx, hi, lo);
     } else if (hi == 0x14 || hi == 0x15 || hi == 0x1c) {
         switch (lo) {
         case 0x20:
             /* resume caption loading */
             ctx->mode = CCMODE_POPON;
             break;
         case 0x24:
             handle_delete_end_of_row(ctx, hi, lo);
             break;
         case 0x25:
         case 0x26:
         case 0x27:
             ctx->rollup = lo - 0x23;
             ctx->mode = CCMODE_ROLLUP;
             break;
         case 0x29:
             /* resume direct captioning */
             ctx->mode = CCMODE_PAINTON;
             break;
         case 0x2b:
             /* resume text display */
             ctx->mode = CCMODE_TEXT;
             break;
         case 0x2c:
             /* erase display memory */
             handle_edm(ctx, pts);
             break;
         case 0x2d:
             /* carriage return */
             ff_dlog(ctx, "carriage return\n");
             if (!ctx->real_time)
                 reap_screen(ctx, pts);
             roll_up(ctx);
             ctx->cursor_column = 0;
             break;
         case 0x2e:
             /* erase buffered (non displayed) memory */
             // Only in realtime mode. In buffered mode, we re-use the inactive screen
             // for our own buffering.
             if (ctx->real_time) {
                 struct Screen *screen = ctx->screen + !ctx->active_screen;
                 screen->row_used = 0;
             }
             break;
         case 0x2f:
             /* end of caption */
             ff_dlog(ctx, "handle_eoc\n");
             handle_eoc(ctx, pts);
             break;
         default:
             ff_dlog(ctx, "Unknown command 0x%hhx 0x%hhx\n", hi, lo);
             break;
         }
     } else if (hi >= 0x20) {
         /* Standard characters (always in pairs) */
         handle_char(ctx, hi, lo, pts);
     } else {
         /* Ignoring all other non data code */
         ff_dlog(ctx, "Unknown command 0x%hhx 0x%hhx\n", hi, lo);
     }

     /* set prev command */
     ctx->prev_cmd[0] = hi;
     ctx->prev_cmd[1] = lo;
 }

 static int decode(AVCodecContext *avctx, void *data, int *got_sub, AVPacket *avpkt)
 {
     CCaptionSubContext *ctx = avctx->priv_data;
     AVSubtitle *sub = data;
     uint8_t *bptr = NULL;
     int len = avpkt->size;
     int ret = 0;
     int i;

     if (ctx->pktbuf->size < len) {
         ret = av_buffer_realloc(&ctx->pktbuf, len);
          if (ret < 0) {
             av_log(ctx, AV_LOG_WARNING, "Insufficient Memory of %d truncated to %d\n", len, ctx->pktbuf->size);
             len = ctx->pktbuf->size;
             ret = 0;
         }
     }
     memcpy(ctx->pktbuf->data, avpkt->data, len);
     bptr = ctx->pktbuf->data;

     for (i  = 0; i < len; i += 3) {
         uint8_t cc_type = *(bptr + i) & 3;
         if (validate_cc_data_pair(bptr + i))
             continue;
         /* ignoring data field 1 */
         if(cc_type == 1)
             continue;
         else
             process_cc608(ctx, avpkt->pts, *(bptr + i + 1) & 0x7f, *(bptr + i + 2) & 0x7f);

         if (!ctx->buffer_changed)
             continue;
         ctx->buffer_changed = 0;

         if (*ctx->buffer.str || ctx->real_time)
         {
             int64_t sub_pts = ctx->real_time ? avpkt->pts : ctx->start_time;
             int start_time = av_rescale_q(sub_pts, avctx->time_base, ass_tb);
             int duration = -1;
             if (!ctx->real_time) {
                 int end_time = av_rescale_q(ctx->end_time, avctx->time_base, ass_tb);
                 duration = end_time - start_time;
             }
             ff_dlog(ctx, "cdp writing data (%s)\n",ctx->buffer.str);
             ret = ff_ass_add_rect_bprint(sub, &ctx->buffer, start_time, duration);
             if (ret < 0)
                 return ret;
             sub->pts = av_rescale_q(sub_pts, avctx->time_base, AV_TIME_BASE_Q);
             ctx->buffer_changed = 0;
             ctx->last_real_time = avpkt->pts;
             ctx->screen_touched = 0;
         }
     }

     if (ctx->real_time && ctx->screen_touched &&
         avpkt->pts > ctx->last_real_time + av_rescale_q(20, ass_tb, avctx->time_base)) {
         int start_time;
         ctx->last_real_time = avpkt->pts;
         ctx->screen_touched = 0;

         capture_screen(ctx);
         ctx->buffer_changed = 0;

         start_time = av_rescale_q(avpkt->pts, avctx->time_base, ass_tb);
         ret = ff_ass_add_rect_bprint(sub, &ctx->buffer, start_time, -1);
         if (ret < 0)
             return ret;
         sub->pts = av_rescale_q(avpkt->pts, avctx->time_base, AV_TIME_BASE_Q);
     }

     *got_sub = sub->num_rects > 0;
     return ret;
 }

 #define OFFSET(x) offsetof(CCaptionSubContext, x)
 #define SD AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM
 static const AVOption options[] = {
     { "real_time", "emit subtitle events as they are decoded for real-time display", OFFSET(real_time), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, SD },
     {NULL}
 };

 static const AVClass ccaption_dec_class = {
     .class_name = "Closed caption Decoder",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };

 AVCodec ff_ccaption_decoder = {
     .name           = "cc_dec",
     .long_name      = NULL_IF_CONFIG_SMALL("Closed Caption (EIA-608 / CEA-708) Decoder"),
     .type           = AVMEDIA_TYPE_SUBTITLE,
     .id             = AV_CODEC_ID_EIA_608,
     .priv_data_size = sizeof(CCaptionSubContext),
     .init           = init_decoder,
     .close          = close_decoder,
     .flush          = flush_decoder,
     .decode         = decode,
     .priv_class     = &ccaption_dec_class,
 };
	/*
	* Closed Caption Decoding
	* Copyright (c) 2015 Anshul Maheshwari
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include "avcodec.h"
	#include "ass.h"
	#include "libavutil/opt.h"

	#define SCREEN_ROWS 15
	#define SCREEN_COLUMNS 32

	#define SET_FLAG(var, val) ( (var) \|= ( 1 << (val)) )
	#define UNSET_FLAG(var, val) ( (var) &= ~( 1 << (val)) )
	#define CHECK_FLAG(var, val) ( (var) & ( 1 << (val)) )

	static const AVRational ass_tb = {1, 100};

	/*
	* TODO list
	* 1) handle font and color completely
	*/
	enum cc_mode {
	CCMODE_POPON,
	CCMODE_PAINTON,
	CCMODE_ROLLUP,
	CCMODE_TEXT,
	};

	enum cc_color_code {
	CCCOL_WHITE,
	CCCOL_GREEN,
	CCCOL_BLUE,
	CCCOL_CYAN,
	CCCOL_RED,
	CCCOL_YELLOW,
	CCCOL_MAGENTA,
	CCCOL_USERDEFINED,
	CCCOL_BLACK,
	CCCOL_TRANSPARENT,
	};

	enum cc_font {
	CCFONT_REGULAR,
	CCFONT_ITALICS,
	CCFONT_UNDERLINED,
	CCFONT_UNDERLINED_ITALICS,
	};

	static const unsigned char pac2_attribs[32][3] = // Color, font, ident
	{
	{ CCCOL_WHITE, CCFONT_REGULAR, 0 }, // 0x40 \|\| 0x60
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 0 }, // 0x41 \|\| 0x61
	{ CCCOL_GREEN, CCFONT_REGULAR, 0 }, // 0x42 \|\| 0x62
	{ CCCOL_GREEN, CCFONT_UNDERLINED, 0 }, // 0x43 \|\| 0x63
	{ CCCOL_BLUE, CCFONT_REGULAR, 0 }, // 0x44 \|\| 0x64
	{ CCCOL_BLUE, CCFONT_UNDERLINED, 0 }, // 0x45 \|\| 0x65
	{ CCCOL_CYAN, CCFONT_REGULAR, 0 }, // 0x46 \|\| 0x66
	{ CCCOL_CYAN, CCFONT_UNDERLINED, 0 }, // 0x47 \|\| 0x67
	{ CCCOL_RED, CCFONT_REGULAR, 0 }, // 0x48 \|\| 0x68
	{ CCCOL_RED, CCFONT_UNDERLINED, 0 }, // 0x49 \|\| 0x69
	{ CCCOL_YELLOW, CCFONT_REGULAR, 0 }, // 0x4a \|\| 0x6a
	{ CCCOL_YELLOW, CCFONT_UNDERLINED, 0 }, // 0x4b \|\| 0x6b
	{ CCCOL_MAGENTA, CCFONT_REGULAR, 0 }, // 0x4c \|\| 0x6c
	{ CCCOL_MAGENTA, CCFONT_UNDERLINED, 0 }, // 0x4d \|\| 0x6d
	{ CCCOL_WHITE, CCFONT_ITALICS, 0 }, // 0x4e \|\| 0x6e
	{ CCCOL_WHITE, CCFONT_UNDERLINED_ITALICS, 0 }, // 0x4f \|\| 0x6f
	{ CCCOL_WHITE, CCFONT_REGULAR, 0 }, // 0x50 \|\| 0x70
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 0 }, // 0x51 \|\| 0x71
	{ CCCOL_WHITE, CCFONT_REGULAR, 4 }, // 0x52 \|\| 0x72
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 4 }, // 0x53 \|\| 0x73
	{ CCCOL_WHITE, CCFONT_REGULAR, 8 }, // 0x54 \|\| 0x74
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 8 }, // 0x55 \|\| 0x75
	{ CCCOL_WHITE, CCFONT_REGULAR, 12 }, // 0x56 \|\| 0x76
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 12 }, // 0x57 \|\| 0x77
	{ CCCOL_WHITE, CCFONT_REGULAR, 16 }, // 0x58 \|\| 0x78
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 16 }, // 0x59 \|\| 0x79
	{ CCCOL_WHITE, CCFONT_REGULAR, 20 }, // 0x5a \|\| 0x7a
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 20 }, // 0x5b \|\| 0x7b
	{ CCCOL_WHITE, CCFONT_REGULAR, 24 }, // 0x5c \|\| 0x7c
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 24 }, // 0x5d \|\| 0x7d
	{ CCCOL_WHITE, CCFONT_REGULAR, 28 }, // 0x5e \|\| 0x7e
	{ CCCOL_WHITE, CCFONT_UNDERLINED, 28 } // 0x5f \|\| 0x7f
	/* total 32 entries */
	};

	struct Screen {
	/* +1 is used to compensate null character of string */
	uint8_t characters[SCREEN_ROWS][SCREEN_COLUMNS+1];
	uint8_t colors[SCREEN_ROWS][SCREEN_COLUMNS+1];
	uint8_t fonts[SCREEN_ROWS][SCREEN_COLUMNS+1];
	/*
	* Bitmask of used rows; if a bit is not set, the
	* corresponding row is not used.
	* for setting row 1 use row \| (1 << 0)
	* for setting row 15 use row \| (1 << 14)
	*/
	int16_t row_used;
	};

	typedef struct CCaptionSubContext {
	AVClass *class;
	int real_time;
	struct Screen screen[2];
	int active_screen;
	uint8_t cursor_row;
	uint8_t cursor_column;
	uint8_t cursor_color;
	uint8_t cursor_font;
	AVBPrint buffer;
	int buffer_changed;
	int rollup;
	enum cc_mode mode;
	int64_t start_time;
	/* visible screen time */
	int64_t startv_time;
	int64_t end_time;
	int screen_touched;
	int64_t last_real_time;
	char prev_cmd[2];
	/* buffer to store pkt data */
	AVBufferRef *pktbuf;
	} CCaptionSubContext;


	static av_cold int init_decoder(AVCodecContext *avctx)
	{
	int ret;
	CCaptionSubContext *ctx = avctx->priv_data;

	av_bprint_init(&ctx->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
	/* taking by default roll up to 2 */
	ctx->mode = CCMODE_ROLLUP;
	ctx->rollup = 2;
	ret = ff_ass_subtitle_header(avctx, "Monospace",
	ASS_DEFAULT_FONT_SIZE,
	ASS_DEFAULT_COLOR,
	ASS_DEFAULT_BACK_COLOR,
	ASS_DEFAULT_BOLD,
	ASS_DEFAULT_ITALIC,
	ASS_DEFAULT_UNDERLINE,
	3,
	ASS_DEFAULT_ALIGNMENT);
	if (ret < 0) {
	return ret;
	}
	/* allocate pkt buffer */
	ctx->pktbuf = av_buffer_alloc(128);
	if (!ctx->pktbuf) {
	ret = AVERROR(ENOMEM);
	}
	return ret;
	}

	static av_cold int close_decoder(AVCodecContext *avctx)
	{
	CCaptionSubContext *ctx = avctx->priv_data;
	av_bprint_finalize(&ctx->buffer, NULL);
	av_buffer_unref(&ctx->pktbuf);
	return 0;
	}

	static void flush_decoder(AVCodecContext *avctx)
	{
	CCaptionSubContext *ctx = avctx->priv_data;
	ctx->screen[0].row_used = 0;
	ctx->screen[1].row_used = 0;
	ctx->prev_cmd[0] = 0;
	ctx->prev_cmd[1] = 0;
	ctx->mode = CCMODE_ROLLUP;
	ctx->rollup = 2;
	ctx->cursor_row = 0;
	ctx->cursor_column = 0;
	ctx->cursor_font = 0;
	ctx->cursor_color = 0;
	ctx->active_screen = 0;
	ctx->last_real_time = 0;
	ctx->screen_touched = 0;
	ctx->buffer_changed = 0;
	av_bprint_clear(&ctx->buffer);
	}

	/**
	* @param ctx closed caption context just to print log
	*/
	static int write_char(CCaptionSubContext ctx, struct Screen screen, char ch)
	{
	uint8_t col = ctx->cursor_column;
	char *row = screen->characters[ctx->cursor_row];
	char *font = screen->fonts[ctx->cursor_row];

	if (col < SCREEN_COLUMNS) {
	row[col] = ch;
	font[col] = ctx->cursor_font;
	if (ch) ctx->cursor_column++;
	return 0;
	}
	/* We have extra space at end only for null character */
	else if (col == SCREEN_COLUMNS && ch == 0) {
	row[col] = ch;
	return 0;
	}
	else {
	av_log(ctx, AV_LOG_WARNING, "Data Ignored since exceeding screen width\n");
	return AVERROR_INVALIDDATA;
	}
	}

	/**
	* This function after validating parity bit, also remove it from data pair.
	* The first byte doesn't pass parity, we replace it with a solid blank
	* and process the pair.
	* If the second byte doesn't pass parity, it returns INVALIDDATA
	* user can ignore the whole pair and pass the other pair.
	*/
	static int validate_cc_data_pair(uint8_t *cc_data_pair)
	{
	uint8_t cc_valid = (*cc_data_pair & 4) >>2;
	uint8_t cc_type = *cc_data_pair & 3;

	if (!cc_valid)
	return AVERROR_INVALIDDATA;

	// if EIA-608 data then verify parity.
	if (cc_type==0 \|\| cc_type==1) {
	if (!av_parity(cc_data_pair[2])) {
	return AVERROR_INVALIDDATA;
	}
	if (!av_parity(cc_data_pair[1])) {
	cc_data_pair[1]=0x7F;
	}
	}

	//Skip non-data
	if ((cc_data_pair[0] == 0xFA \|\| cc_data_pair[0] == 0xFC \|\| cc_data_pair[0] == 0xFD)
	&& (cc_data_pair[1] & 0x7F) == 0 && (cc_data_pair[2] & 0x7F) == 0)
	return AVERROR_PATCHWELCOME;

	//skip 708 data
	if (cc_type == 3 \|\| cc_type == 2)
	return AVERROR_PATCHWELCOME;

	/* remove parity bit */
	cc_data_pair[1] &= 0x7F;
	cc_data_pair[2] &= 0x7F;

	return 0;
	}

	static struct Screen get_writing_screen(CCaptionSubContext ctx)
	{
	switch (ctx->mode) {
	case CCMODE_POPON:
	// use Inactive screen
	return ctx->screen + !ctx->active_screen;
	case CCMODE_PAINTON:
	case CCMODE_ROLLUP:
	case CCMODE_TEXT:
	// use active screen
	return ctx->screen + ctx->active_screen;
	}
	/* It was never an option */
	return NULL;
	}

	static void roll_up(CCaptionSubContext *ctx)
	{
	struct Screen *screen;
	int i, keep_lines;

	if (ctx->mode == CCMODE_TEXT)
	return;

	screen = get_writing_screen(ctx);

	/* +1 signify cursor_row starts from 0
	* Can't keep lines less then row cursor pos
	*/
	keep_lines = FFMIN(ctx->cursor_row + 1, ctx->rollup);

	for (i = 0; i < SCREEN_ROWS; i++) {
	if (i > ctx->cursor_row - keep_lines && i <= ctx->cursor_row)
	continue;
	UNSET_FLAG(screen->row_used, i);
	}

	for (i = 0; i < keep_lines && screen->row_used; i++) {
	const int i_row = ctx->cursor_row - keep_lines + i + 1;

	memcpy(screen->characters[i_row], screen->characters[i_row+1], SCREEN_COLUMNS);
	memcpy(screen->colors[i_row], screen->colors[i_row+1], SCREEN_COLUMNS);
	memcpy(screen->fonts[i_row], screen->fonts[i_row+1], SCREEN_COLUMNS);
	if (CHECK_FLAG(screen->row_used, i_row + 1))
	SET_FLAG(screen->row_used, i_row);
	}

	UNSET_FLAG(screen->row_used, ctx->cursor_row);
	}

	static int capture_screen(CCaptionSubContext *ctx)
	{
	int i;
	struct Screen *screen = ctx->screen + ctx->active_screen;
	enum cc_font prev_font = CCFONT_REGULAR;
	av_bprint_clear(&ctx->buffer);

	for (i = 0; screen->row_used && i < SCREEN_ROWS; i++)
	{
	if (CHECK_FLAG(screen->row_used, i)) {
	const char *row = screen->characters[i];
	const char *font = screen->fonts[i];
	int j = 0;

	/* skip leading space */
	while (row[j] == ' ')
	j++;

	for (; j < SCREEN_COLUMNS; j++) {
	const char e_tag = "", s_tag = "";

	if (row[j] == 0)
	break;

	if (prev_font != font[j]) {
	switch (prev_font) {
	case CCFONT_ITALICS:
	e_tag = "{\\i0}";
	break;
	case CCFONT_UNDERLINED:
	e_tag = "{\\u0}";
	break;
	case CCFONT_UNDERLINED_ITALICS:
	e_tag = "{\\u0}{\\i0}";
	break;
	}
	switch (font[j]) {
	case CCFONT_ITALICS:
	s_tag = "{\\i1}";
	break;
	case CCFONT_UNDERLINED:
	s_tag = "{\\u1}";
	break;
	case CCFONT_UNDERLINED_ITALICS:
	s_tag = "{\\u1}{\\i1}";
	break;
	}
	}
	prev_font = font[j];
	av_bprintf(&ctx->buffer, "%s%s%c", e_tag, s_tag, row[j]);
	}
	av_bprintf(&ctx->buffer, "\\N");
	}
	}
	if (!av_bprint_is_complete(&ctx->buffer))
	return AVERROR(ENOMEM);
	if (screen->row_used && ctx->buffer.len >= 2) {
	ctx->buffer.len -= 2;
	ctx->buffer.str[ctx->buffer.len] = 0;
	}
	ctx->buffer_changed = 1;
	return 0;
	}

	static int reap_screen(CCaptionSubContext *ctx, int64_t pts)
	{
	ctx->start_time = ctx->startv_time;
	ctx->startv_time = pts;
	ctx->end_time = pts;
	return capture_screen(ctx);
	}

	static void handle_textattr(CCaptionSubContext *ctx, uint8_t hi, uint8_t lo)
	{
	int i = lo - 0x20;
	struct Screen *screen = get_writing_screen(ctx);

	if (i >= 32)
	return;

	ctx->cursor_color = pac2_attribs[i][0];
	ctx->cursor_font = pac2_attribs[i][1];

	SET_FLAG(screen->row_used, ctx->cursor_row);
	write_char(ctx, screen, ' ');
	}

	static void handle_pac(CCaptionSubContext *ctx, uint8_t hi, uint8_t lo)
	{
	static const int8_t row_map[] = {
	11, -1, 1, 2, 3, 4, 12, 13, 14, 15, 5, 6, 7, 8, 9, 10
	};
	const int index = ( (hi<<1) & 0x0e) \| ( (lo>>5) & 0x01 );
	struct Screen *screen = get_writing_screen(ctx);
	int indent, i;

	if (row_map[index] <= 0) {
	av_log(ctx, AV_LOG_DEBUG, "Invalid pac index encountered\n");
	return;
	}

	lo &= 0x1f;

	ctx->cursor_row = row_map[index] - 1;
	ctx->cursor_color = pac2_attribs[lo][0];
	ctx->cursor_font = pac2_attribs[lo][1];
	ctx->cursor_column = 0;
	indent = pac2_attribs[lo][2];
	for (i = 0; i < indent; i++) {
	write_char(ctx, screen, ' ');
	}
	}

	/**
	* @param pts it is required to set end time
	*/
	static void handle_edm(CCaptionSubContext *ctx, int64_t pts)
	{
	struct Screen *screen = ctx->screen + ctx->active_screen;

	// In buffered mode, keep writing to screen until it is wiped.
	// Before wiping the display, capture contents to emit subtitle.
	if (!ctx->real_time)
	reap_screen(ctx, pts);

	screen->row_used = 0;

	// In realtime mode, emit an empty caption so the last one doesn't
	// stay on the screen.
	if (ctx->real_time)
	reap_screen(ctx, pts);
	}

	static void handle_eoc(CCaptionSubContext *ctx, int64_t pts)
	{
	// In buffered mode, we wait til the next EOC and
	// reap what was already on the screen since the last EOC.
	if (!ctx->real_time)
	handle_edm(ctx,pts);

	ctx->active_screen = !ctx->active_screen;
	ctx->cursor_column = 0;

	// In realtime mode, we display the buffered contents (after
	// flipping the buffer to active above) as soon as EOC arrives.
	if (ctx->real_time)
	reap_screen(ctx, pts);
	}

	static void handle_delete_end_of_row(CCaptionSubContext *ctx, char hi, char lo)
	{
	struct Screen *screen = get_writing_screen(ctx);
	write_char(ctx, screen, 0);
	}

	static void handle_char(CCaptionSubContext *ctx, char hi, char lo, int64_t pts)
	{
	struct Screen *screen = get_writing_screen(ctx);

	SET_FLAG(screen->row_used, ctx->cursor_row);

	write_char(ctx, screen, hi);

	if (lo) {
	write_char(ctx, screen, lo);
	}
	write_char(ctx, screen, 0);

	if (ctx->mode != CCMODE_POPON)
	ctx->screen_touched = 1;

	/* reset prev command since character can repeat */
	ctx->prev_cmd[0] = 0;
	ctx->prev_cmd[1] = 0;
	if (lo)
	ff_dlog(ctx, "(%c,%c)\n", hi, lo);
	else
	ff_dlog(ctx, "(%c)\n", hi);
	}

	static void process_cc608(CCaptionSubContext *ctx, int64_t pts, uint8_t hi, uint8_t lo)
	{
	if (hi == ctx->prev_cmd[0] && lo == ctx->prev_cmd[1]) {
	/* ignore redundant command */
	} else if ( (hi == 0x10 && (lo >= 0x40 && lo <= 0x5f)) \|\|
	( (hi >= 0x11 && hi <= 0x17) && (lo >= 0x40 && lo <= 0x7f) ) ) {
	handle_pac(ctx, hi, lo);
	} else if ( ( hi == 0x11 && lo >= 0x20 && lo <= 0x2f ) \|\|
	( hi == 0x17 && lo >= 0x2e && lo <= 0x2f) ) {
	handle_textattr(ctx, hi, lo);
	} else if (hi == 0x14 \|\| hi == 0x15 \|\| hi == 0x1c) {
	switch (lo) {
	case 0x20:
	/* resume caption loading */
	ctx->mode = CCMODE_POPON;
	break;
	case 0x24:
	handle_delete_end_of_row(ctx, hi, lo);
	break;
	case 0x25:
	case 0x26:
	case 0x27:
	ctx->rollup = lo - 0x23;
	ctx->mode = CCMODE_ROLLUP;
	break;
	case 0x29:
	/* resume direct captioning */
	ctx->mode = CCMODE_PAINTON;
	break;
	case 0x2b:
	/* resume text display */
	ctx->mode = CCMODE_TEXT;
	break;
	case 0x2c:
	/* erase display memory */
	handle_edm(ctx, pts);
	break;
	case 0x2d:
	/* carriage return */
	ff_dlog(ctx, "carriage return\n");
	if (!ctx->real_time)
	reap_screen(ctx, pts);
	roll_up(ctx);
	ctx->cursor_column = 0;
	break;
	case 0x2e:
	/* erase buffered (non displayed) memory */
	// Only in realtime mode. In buffered mode, we re-use the inactive screen
	// for our own buffering.
	if (ctx->real_time) {
	struct Screen *screen = ctx->screen + !ctx->active_screen;
	screen->row_used = 0;
	}
	break;
	case 0x2f:
	/* end of caption */
	ff_dlog(ctx, "handle_eoc\n");
	handle_eoc(ctx, pts);
	break;
	default:
	ff_dlog(ctx, "Unknown command 0x%hhx 0x%hhx\n", hi, lo);
	break;
	}
	} else if (hi >= 0x20) {
	/* Standard characters (always in pairs) */
	handle_char(ctx, hi, lo, pts);
	} else {
	/* Ignoring all other non data code */
	ff_dlog(ctx, "Unknown command 0x%hhx 0x%hhx\n", hi, lo);
	}

	/* set prev command */
	ctx->prev_cmd[0] = hi;
	ctx->prev_cmd[1] = lo;
	}

	static int decode(AVCodecContext avctx, void data, int got_sub, AVPacket avpkt)
	{
	CCaptionSubContext *ctx = avctx->priv_data;
	AVSubtitle *sub = data;
	uint8_t *bptr = NULL;
	int len = avpkt->size;
	int ret = 0;
	int i;

	if (ctx->pktbuf->size < len) {
	ret = av_buffer_realloc(&ctx->pktbuf, len);
	if (ret < 0) {
	av_log(ctx, AV_LOG_WARNING, "Insufficient Memory of %d truncated to %d\n", len, ctx->pktbuf->size);
	len = ctx->pktbuf->size;
	ret = 0;
	}
	}
	memcpy(ctx->pktbuf->data, avpkt->data, len);
	bptr = ctx->pktbuf->data;

	for (i = 0; i < len; i += 3) {
	uint8_t cc_type = *(bptr + i) & 3;
	if (validate_cc_data_pair(bptr + i))
	continue;
	/* ignoring data field 1 */
	if(cc_type == 1)
	continue;
	else
	process_cc608(ctx, avpkt->pts, (bptr + i + 1) & 0x7f, (bptr + i + 2) & 0x7f);

	if (!ctx->buffer_changed)
	continue;
	ctx->buffer_changed = 0;

	if (*ctx->buffer.str \|\| ctx->real_time)
	{
	int64_t sub_pts = ctx->real_time ? avpkt->pts : ctx->start_time;
	int start_time = av_rescale_q(sub_pts, avctx->time_base, ass_tb);
	int duration = -1;
	if (!ctx->real_time) {
	int end_time = av_rescale_q(ctx->end_time, avctx->time_base, ass_tb);
	duration = end_time - start_time;
	}
	ff_dlog(ctx, "cdp writing data (%s)\n",ctx->buffer.str);
	ret = ff_ass_add_rect_bprint(sub, &ctx->buffer, start_time, duration);
	if (ret < 0)
	return ret;
	sub->pts = av_rescale_q(sub_pts, avctx->time_base, AV_TIME_BASE_Q);
	ctx->buffer_changed = 0;
	ctx->last_real_time = avpkt->pts;
	ctx->screen_touched = 0;
	}
	}

	if (ctx->real_time && ctx->screen_touched &&
	avpkt->pts > ctx->last_real_time + av_rescale_q(20, ass_tb, avctx->time_base)) {
	int start_time;
	ctx->last_real_time = avpkt->pts;
	ctx->screen_touched = 0;

	capture_screen(ctx);
	ctx->buffer_changed = 0;

	start_time = av_rescale_q(avpkt->pts, avctx->time_base, ass_tb);
	ret = ff_ass_add_rect_bprint(sub, &ctx->buffer, start_time, -1);
	if (ret < 0)
	return ret;
	sub->pts = av_rescale_q(avpkt->pts, avctx->time_base, AV_TIME_BASE_Q);
	}

	*got_sub = sub->num_rects > 0;
	return ret;
	}

	#define OFFSET(x) offsetof(CCaptionSubContext, x)
	#define SD AV_OPT_FLAG_SUBTITLE_PARAM \| AV_OPT_FLAG_DECODING_PARAM
	static const AVOption options[] = {
	{ "real_time", "emit subtitle events as they are decoded for real-time display", OFFSET(real_time), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, SD },
	{NULL}
	};

	static const AVClass ccaption_dec_class = {
	.class_name = "Closed caption Decoder",
	.item_name = av_default_item_name,
	.option = options,
	.version = LIBAVUTIL_VERSION_INT,
	};

	AVCodec ff_ccaption_decoder = {
	.name = "cc_dec",
	.long_name = NULL_IF_CONFIG_SMALL("Closed Caption (EIA-608 / CEA-708) Decoder"),
	.type = AVMEDIA_TYPE_SUBTITLE,
	.id = AV_CODEC_ID_EIA_608,
	.priv_data_size = sizeof(CCaptionSubContext),
	.init = init_decoder,
	.close = close_decoder,
	.flush = flush_decoder,
	.decode = decode,
	.priv_class = &ccaption_dec_class,
	};