The positioning was completely wrong. First, the coordinates are expressed in ASS playback resolution (which is by default 384x288). Secondly, the coordinates define a drawing rectangle, not a moving area. The previous code was making subtitles move from a random position to another random position. Here we rescale assuming the video resolution is a DVD one (720x480). We can't really do anything better so far, but since this positioning information is often from a DVD rip we can consider them relatively safe.
		
			
				
	
	
		
			262 lines
		
	
	
		
			10 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			262 lines
		
	
	
		
			10 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
/*
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 * SubRip subtitle decoder
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 * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "libavutil/avstring.h"
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#include "libavutil/common.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/parseutils.h"
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#include "avcodec.h"
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#include "ass.h"
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static int html_color_parse(AVCodecContext *avctx, const char *str)
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{
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    uint8_t rgba[4];
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    if (av_parse_color(rgba, str, strcspn(str, "\" >"), avctx) < 0)
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        return -1;
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    return rgba[0] | rgba[1] << 8 | rgba[2] << 16;
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}
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enum {
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    PARAM_UNKNOWN = -1,
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    PARAM_SIZE,
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    PARAM_COLOR,
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    PARAM_FACE,
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    PARAM_NUMBER
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};
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typedef struct SrtStack {
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    char tag[128];
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    char param[PARAM_NUMBER][128];
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} SrtStack;
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static void rstrip_spaces_buf(AVBPrint *buf)
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{
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    while (buf->len > 0 && buf->str[buf->len - 1] == ' ')
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        buf->str[--buf->len] = 0;
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}
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static void srt_to_ass(AVCodecContext *avctx, AVBPrint *dst,
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                       const char *in, int x1, int y1, int x2, int y2)
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{
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    char *param, buffer[128], tmp[128];
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    int len, tag_close, sptr = 1, line_start = 1, an = 0, end = 0;
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    SrtStack stack[16];
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    stack[0].tag[0] = 0;
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    strcpy(stack[0].param[PARAM_SIZE],  "{\\fs}");
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    strcpy(stack[0].param[PARAM_COLOR], "{\\c}");
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    strcpy(stack[0].param[PARAM_FACE],  "{\\fn}");
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    if (x1 >= 0 && y1 >= 0) {
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        /* XXX: here we rescale coordinate assuming they are in DVD resolution
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         * (720x480) since we don't have anything better */
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        if (x2 >= 0 && y2 >= 0 && (x2 != x1 || y2 != y1) && x2 >= x1 && y2 >= y1) {
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            /* text rectangle defined, write the text at the center of the rectangle */
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            const int cx = x1 + (x2 - x1)/2;
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            const int cy = y1 + (y2 - y1)/2;
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            const int scaled_x = cx * ASS_DEFAULT_PLAYRESX / 720;
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            const int scaled_y = cy * ASS_DEFAULT_PLAYRESY / 480;
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            av_bprintf(dst, "{\\an5}{\\pos(%d,%d)}", scaled_x, scaled_y);
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        } else {
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            /* only the top left corner, assume the text starts in that corner */
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            const int scaled_x = x1 * ASS_DEFAULT_PLAYRESX / 720;
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            const int scaled_y = y1 * ASS_DEFAULT_PLAYRESY / 480;
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            av_bprintf(dst, "{\\an1}{\\pos(%d,%d)}", scaled_x, scaled_y);
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        }
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    }
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    for (; !end && *in; in++) {
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        switch (*in) {
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        case '\r':
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            break;
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        case '\n':
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            if (line_start) {
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                end = 1;
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                break;
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            }
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            rstrip_spaces_buf(dst);
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            av_bprintf(dst, "\\N");
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            line_start = 1;
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            break;
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        case ' ':
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            if (!line_start)
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                av_bprint_chars(dst, *in, 1);
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            break;
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        case '{':    /* skip all {\xxx} substrings except for {\an%d}
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                        and all microdvd like styles such as {Y:xxx} */
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            len = 0;
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            an += sscanf(in, "{\\an%*1u}%n", &len) >= 0 && len > 0;
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            if ((an != 1 && (len = 0, sscanf(in, "{\\%*[^}]}%n", &len) >= 0 && len > 0)) ||
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                (len = 0, sscanf(in, "{%*1[CcFfoPSsYy]:%*[^}]}%n", &len) >= 0 && len > 0)) {
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                in += len - 1;
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            } else
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                av_bprint_chars(dst, *in, 1);
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            break;
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        case '<':
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            tag_close = in[1] == '/';
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            len = 0;
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            if (sscanf(in+tag_close+1, "%127[^>]>%n", buffer, &len) >= 1 && len > 0) {
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                if ((param = strchr(buffer, ' ')))
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                    *param++ = 0;
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                if ((!tag_close && sptr < FF_ARRAY_ELEMS(stack)) ||
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                    ( tag_close && sptr > 0 && !strcmp(stack[sptr-1].tag, buffer))) {
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                    int i, j, unknown = 0;
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                    in += len + tag_close;
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                    if (!tag_close)
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                        memset(stack+sptr, 0, sizeof(*stack));
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                    if (!strcmp(buffer, "font")) {
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                        if (tag_close) {
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                            for (i=PARAM_NUMBER-1; i>=0; i--)
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                                if (stack[sptr-1].param[i][0])
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                                    for (j=sptr-2; j>=0; j--)
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                                        if (stack[j].param[i][0]) {
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                                            av_bprintf(dst, "%s", stack[j].param[i]);
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                                            break;
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                                        }
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                        } else {
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                            while (param) {
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                                if (!strncmp(param, "size=", 5)) {
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                                    unsigned font_size;
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                                    param += 5 + (param[5] == '"');
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                                    if (sscanf(param, "%u", &font_size) == 1) {
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                                        snprintf(stack[sptr].param[PARAM_SIZE],
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                                             sizeof(stack[0].param[PARAM_SIZE]),
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                                             "{\\fs%u}", font_size);
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                                    }
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                                } else if (!strncmp(param, "color=", 6)) {
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                                    param += 6 + (param[6] == '"');
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                                    snprintf(stack[sptr].param[PARAM_COLOR],
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                                         sizeof(stack[0].param[PARAM_COLOR]),
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                                         "{\\c&H%X&}",
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                                         html_color_parse(avctx, param));
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                                } else if (!strncmp(param, "face=", 5)) {
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                                    param += 5 + (param[5] == '"');
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                                    len = strcspn(param,
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                                                  param[-1] == '"' ? "\"" :" ");
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                                    av_strlcpy(tmp, param,
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                                               FFMIN(sizeof(tmp), len+1));
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                                    param += len;
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                                    snprintf(stack[sptr].param[PARAM_FACE],
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                                             sizeof(stack[0].param[PARAM_FACE]),
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                                             "{\\fn%s}", tmp);
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                                }
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                                if ((param = strchr(param, ' ')))
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                                    param++;
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                            }
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                            for (i=0; i<PARAM_NUMBER; i++)
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                                if (stack[sptr].param[i][0])
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                                    av_bprintf(dst, "%s", stack[sptr].param[i]);
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                        }
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                    } else if (!buffer[1] && strspn(buffer, "bisu") == 1) {
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                        av_bprintf(dst, "{\\%c%d}", buffer[0], !tag_close);
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                    } else {
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                        unknown = 1;
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                        snprintf(tmp, sizeof(tmp), "</%s>", buffer);
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                    }
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                    if (tag_close) {
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                        sptr--;
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                    } else if (unknown && !strstr(in, tmp)) {
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                        in -= len + tag_close;
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                        av_bprint_chars(dst, *in, 1);
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                    } else
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                        av_strlcpy(stack[sptr++].tag, buffer,
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                                   sizeof(stack[0].tag));
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                    break;
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                }
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            }
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        default:
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            av_bprint_chars(dst, *in, 1);
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            break;
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        }
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        if (*in != ' ' && *in != '\r' && *in != '\n')
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            line_start = 0;
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    }
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    while (dst->len >= 2 && !strncmp(&dst->str[dst->len - 2], "\\N", 2))
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        dst->len -= 2;
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    dst->str[dst->len] = 0;
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    rstrip_spaces_buf(dst);
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}
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static int srt_decode_frame(AVCodecContext *avctx,
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                            void *data, int *got_sub_ptr, AVPacket *avpkt)
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{
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    AVSubtitle *sub = data;
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    AVBPrint buffer;
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    int ts_start, ts_end, x1 = -1, y1 = -1, x2 = -1, y2 = -1;
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    int size, ret;
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    const uint8_t *p = av_packet_get_side_data(avpkt, AV_PKT_DATA_SUBTITLE_POSITION, &size);
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    if (p && size == 16) {
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        x1 = AV_RL32(p     );
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        y1 = AV_RL32(p +  4);
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        x2 = AV_RL32(p +  8);
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        y2 = AV_RL32(p + 12);
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    }
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    if (avpkt->size <= 0)
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        return avpkt->size;
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    av_bprint_init(&buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
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        // TODO: reindent
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            // Do final divide-by-10 outside rescale to force rounding down.
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            ts_start = av_rescale_q(avpkt->pts,
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                                    avctx->time_base,
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                                    (AVRational){1,100});
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            ts_end   = av_rescale_q(avpkt->pts + avpkt->duration,
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                                    avctx->time_base,
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                                    (AVRational){1,100});
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    srt_to_ass(avctx, &buffer, avpkt->data, x1, y1, x2, y2);
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    ret = ff_ass_add_rect_bprint(sub, &buffer, ts_start, ts_end-ts_start);
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    av_bprint_finalize(&buffer, NULL);
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    if (ret < 0)
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        return ret;
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    *got_sub_ptr = sub->num_rects > 0;
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    return avpkt->size;
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}
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#if CONFIG_SRT_DECODER
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/* deprecated decoder */
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AVCodec ff_srt_decoder = {
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    .name         = "srt",
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    .long_name    = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
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    .type         = AVMEDIA_TYPE_SUBTITLE,
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    .id           = AV_CODEC_ID_SUBRIP,
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    .init         = ff_ass_subtitle_header_default,
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    .decode       = srt_decode_frame,
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};
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#endif
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#if CONFIG_SUBRIP_DECODER
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AVCodec ff_subrip_decoder = {
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    .name         = "subrip",
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    .long_name    = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
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    .type         = AVMEDIA_TYPE_SUBTITLE,
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    .id           = AV_CODEC_ID_SUBRIP,
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    .init         = ff_ass_subtitle_header_default,
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    .decode       = srt_decode_frame,
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};
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#endif
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