/*
  * 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 ms_tb = {1, 1000};

 /*
  * 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,

 };
 

 enum cc_charset {
     CCSET_BASIC_AMERICAN,
     CCSET_SPECIAL_AMERICAN,
     CCSET_EXTENDED_SPANISH_FRENCH_MISC,
     CCSET_EXTENDED_PORTUGUESE_GERMAN_DANISH,
 };
 
 static const char *charset_overrides[4][128] =
 {
     [CCSET_BASIC_AMERICAN] = {
         [0x27] = "\u2019",
         [0x2a] = "\u00e1",
         [0x5c] = "\u00e9",
         [0x5e] = "\u00ed",
         [0x5f] = "\u00f3",
         [0x60] = "\u00fa",
         [0x7b] = "\u00e7",
         [0x7c] = "\u00f7",
         [0x7d] = "\u00d1",
         [0x7e] = "\u00f1",
         [0x7f] = "\u2588"
     },
     [CCSET_SPECIAL_AMERICAN] = {
         [0x30] = "\u00ae",
         [0x31] = "\u00b0",
         [0x32] = "\u00bd",
         [0x33] = "\u00bf",
         [0x34] = "\u2122",
         [0x35] = "\u00a2",
         [0x36] = "\u00a3",
         [0x37] = "\u266a",
         [0x38] = "\u00e0",
         [0x39] = "\u00A0",
         [0x3a] = "\u00e8",
         [0x3b] = "\u00e2",
         [0x3c] = "\u00ea",
         [0x3d] = "\u00ee",
         [0x3e] = "\u00f4",
         [0x3f] = "\u00fb",
     },
     [CCSET_EXTENDED_SPANISH_FRENCH_MISC] = {
         [0x20] = "\u00c1",
         [0x21] = "\u00c9",
         [0x22] = "\u00d3",
         [0x23] = "\u00da",
         [0x24] = "\u00dc",
         [0x25] = "\u00fc",
         [0x26] = "\u00b4",
         [0x27] = "\u00a1",
         [0x28] = "*",
         [0x29] = "\u2018",
         [0x2a] = "-",
         [0x2b] = "\u00a9",
         [0x2c] = "\u2120",
         [0x2d] = "\u00b7",
         [0x2e] = "\u201c",
         [0x2f] = "\u201d",
         [0x30] = "\u00c0",
         [0x31] = "\u00c2",
         [0x32] = "\u00c7",
         [0x33] = "\u00c8",
         [0x34] = "\u00ca",
         [0x35] = "\u00cb",
         [0x36] = "\u00eb",
         [0x37] = "\u00ce",
         [0x38] = "\u00cf",
         [0x39] = "\u00ef",
         [0x3a] = "\u00d4",
         [0x3b] = "\u00d9",
         [0x3c] = "\u00f9",
         [0x3d] = "\u00db",
         [0x3e] = "\u00ab",
         [0x3f] = "\u00bb",
     },
     [CCSET_EXTENDED_PORTUGUESE_GERMAN_DANISH] = {
         [0x20] = "\u00c3",
         [0x21] = "\u00e3",
         [0x22] = "\u00cd",
         [0x23] = "\u00cc",
         [0x24] = "\u00ec",
         [0x25] = "\u00d2",
         [0x26] = "\u00f2",
         [0x27] = "\u00d5",
         [0x28] = "\u00f5",
         [0x29] = "{",
         [0x2a] = "}",
         [0x2b] = "\\",
         [0x2c] = "^",
         [0x2d] = "_",
         [0x2e] = "|",
         [0x2f] = "~",
         [0x30] = "\u00c4",
         [0x31] = "\u00e4",
         [0x32] = "\u00d6",
         [0x33] = "\u00f6",
         [0x34] = "\u00df",
         [0x35] = "\u00a5",
         [0x36] = "\u00a4",
         [0x37] = "\u00a6",
         [0x38] = "\u00c5",
         [0x39] = "\u00e5",
         [0x3a] = "\u00d8",
         [0x3b] = "\u00f8",
         [0x3c] = "\u250c",
         [0x3d] = "\u2510",
         [0x3e] = "\u2514",
         [0x3f] = "\u2518",
     },
 };
 

 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 charsets[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;

     uint8_t cursor_charset;

     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 */

     uint8_t *pktbuf;
     int pktbuf_size;

     int readorder;

 } 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;

     ctx->cursor_row = 10;

     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;

     }

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

     av_bprint_finalize(&ctx->buffer, NULL);

     av_freep(&ctx->pktbuf);
     ctx->pktbuf_size = 0;

     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 = 10;

     ctx->cursor_column = 0;
     ctx->cursor_font = 0;
     ctx->cursor_color = 0;

     ctx->cursor_charset = 0;

     ctx->active_screen = 0;

     ctx->last_real_time = 0;
     ctx->screen_touched = 0;

     ctx->buffer_changed = 0;

     if (!(avctx->flags2 & AV_CODEC_FLAG2_RO_FLUSH_NOOP))
         ctx->readorder = 0;

     av_bprint_clear(&ctx->buffer);
 }
 

 /**
  * @param ctx closed caption context just to print log
  */

 static void 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];

     char *charset = screen->charsets[ctx->cursor_row];

     if (col < SCREEN_COLUMNS) {

         row[col] = ch;

         font[col] = ctx->cursor_font;

         charset[col] = ctx->cursor_charset;
         ctx->cursor_charset = CCSET_BASIC_AMERICAN;

         if (ch) ctx->cursor_column++;

         return;

     }
     /* We have extra space at end only for null character */

     else if (col == SCREEN_COLUMNS && ch == 0) {

         row[col] = ch;

         return;

     }
     else {

         av_log(ctx, AV_LOG_WARNING, "Data Ignored since exceeding screen width\n");

         return;

     }
 }

 /**
  * 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);

         memcpy(screen->charsets[i_row], screen->charsets[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, j, tab = 0;

     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 *charset = screen->charsets[i];
             j = 0;
             while (row[j] == ' ' && charset[j] == CCSET_BASIC_AMERICAN)
                 j++;
             if (!tab || j < tab)
                 tab = j;
         }
     }
 
     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];

             const char *charset = screen->charsets[i];
             const char *override;

             int x, y, seen_char = 0;
             j = 0;

 
             /* skip leading space */

             while (row[j] == ' ' && charset[j] == CCSET_BASIC_AMERICAN && j < tab)

                 j++;
 

             x = ASS_DEFAULT_PLAYRESX * (0.1 + 0.0250 * j);
             y = ASS_DEFAULT_PLAYRESY * (0.1 + 0.0533 * i);
             av_bprintf(&ctx->buffer, "{\\an7}{\\pos(%d,%d)}", x, y);
 

             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];

                 override = charset_overrides[(int)charset[j]][(int)row[j]];
                 if (override) {
                     av_bprintf(&ctx->buffer, "%s%s%s", e_tag, s_tag, override);

                     seen_char = 1;
                 } else if (row[j] == ' ' && !seen_char) {
                     av_bprintf(&ctx->buffer, "%s%s\\h", e_tag, s_tag);

                 } else {
                     av_bprintf(&ctx->buffer, "%s%s%c", e_tag, s_tag, row[j]);

                     seen_char = 1;

                 }

             }
             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_charset = CCSET_BASIC_AMERICAN;

     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);

     switch (hi) {
       case 0x11:
         ctx->cursor_charset = CCSET_SPECIAL_AMERICAN;
         break;
       case 0x12:
         if (ctx->cursor_column > 0)
             ctx->cursor_column -= 1;
         ctx->cursor_charset = CCSET_EXTENDED_SPANISH_FRENCH_MISC;
         break;
       case 0x13:
         if (ctx->cursor_column > 0)
             ctx->cursor_column -= 1;
         ctx->cursor_charset = CCSET_EXTENDED_PORTUGUESE_GERMAN_DANISH;
         break;
       default:
         ctx->cursor_charset = CCSET_BASIC_AMERICAN;
         write_char(ctx, screen, hi);
         break;
     }

     if (lo) {

         write_char(ctx, screen, lo);

     }

     write_char(ctx, screen, 0);

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

     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 */

         return;
     }
 
     /* set prev command */
     ctx->prev_cmd[0] = hi;
     ctx->prev_cmd[1] = lo;
 
     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 >= 0x11 && hi <= 0x13) {
         /* Special characters */
         handle_char(ctx, hi, lo, pts);

     } else if (hi >= 0x20) {

         /* Standard characters (always in pairs) */

         handle_char(ctx, hi, lo, pts);

         ctx->prev_cmd[0] = ctx->prev_cmd[1] = 0;

     } else if (hi == 0x17 && lo >= 0x21 && lo <= 0x23) {

         int i;

         /* Tab offsets (spacing) */

         for (i = 0; i < lo - 0x20; i++) {

             handle_char(ctx, ' ', 0, pts);
         }

     } else {

         /* Ignoring all other non data code */

         ff_dlog(ctx, "Unknown command 0x%hhx 0x%hhx\n", hi, lo);

     }
 }

 static int decode(AVCodecContext *avctx, void *data, int *got_sub, AVPacket *avpkt)
 {
     CCaptionSubContext *ctx = avctx->priv_data;
     AVSubtitle *sub = data;

     const int64_t start_time = sub->pts;

     uint8_t *bptr = NULL;
     int len = avpkt->size;
     int ret = 0;
     int i;
 

     av_fast_padded_malloc(&ctx->pktbuf, &ctx->pktbuf_size, len);
     if (!ctx->pktbuf) {
         av_log(ctx, AV_LOG_WARNING, "Insufficient Memory of %d truncated to %d\n", len, ctx->pktbuf_size);
         return AVERROR(ENOMEM);

     }

     memcpy(ctx->pktbuf, avpkt->data, len);
     bptr = ctx->pktbuf;

 
     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, start_time, *(bptr + i + 1) & 0x7f, *(bptr + i + 2) & 0x7f);

 
         if (!ctx->buffer_changed)
             continue;
         ctx->buffer_changed = 0;
 
         if (*ctx->buffer.str || ctx->real_time)

         {

             ff_dlog(ctx, "cdp writing data (%s)\n",ctx->buffer.str);

             ret = ff_ass_add_rect(sub, ctx->buffer.str, ctx->readorder++, 0, NULL, NULL);

             if (ret < 0)
                 return ret;

             sub->pts = ctx->start_time;

             if (!ctx->real_time)
                 sub->end_display_time = av_rescale_q(ctx->end_time - ctx->start_time,

                                                      AV_TIME_BASE_Q, ms_tb);

             else
                 sub->end_display_time = -1;

             ctx->buffer_changed = 0;

             ctx->last_real_time = sub->pts;

             ctx->screen_touched = 0;

         }
     }
 

     if (ctx->real_time && ctx->screen_touched &&

         sub->pts > ctx->last_real_time + av_rescale_q(200, ms_tb, AV_TIME_BASE_Q)) {
         ctx->last_real_time = sub->pts;

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

         ret = ff_ass_add_rect(sub, ctx->buffer.str, ctx->readorder++, 0, NULL, NULL);

         if (ret < 0)
             return ret;

         sub->end_display_time = -1;

     }
 

     *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)"),

     .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,
 };