mpv/demux/demux_subreader.c

/*
 * Subtitle reader with format autodetection
 *
 * Copyright (c) 2001 laaz
 * Some code cleanup & realloc() by A'rpi/ESP-team
 *
 * This file is part of mpv.
 *
 * mpv is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * mpv 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <dirent.h>

#include <libavutil/common.h>
#include <libavutil/avstring.h>

#include "config.h"
#include "common/msg.h"
#include "common/common.h"
#include "options/options.h"
#include "stream/stream.h"
#include "demux/demux.h"

#define ERR ((void *) -1)

// subtitle formats
#define SUB_INVALID   -1
#define SUB_MICRODVD  0
#define SUB_SUBRIP    1
#define SUB_SUBVIEWER 2
#define SUB_SSA       3
#define SUB_SUBVIEWER2 4
#define SUB_SUBRIP09 5
#define SUB_MPL2     6

#define SUB_MAX_TEXT 12
#define SUB_ALIGNMENT_BOTTOMLEFT       1
#define SUB_ALIGNMENT_BOTTOMCENTER     2
#define SUB_ALIGNMENT_BOTTOMRIGHT      3
#define SUB_ALIGNMENT_MIDDLELEFT       4
#define SUB_ALIGNMENT_MIDDLECENTER     5
#define SUB_ALIGNMENT_MIDDLERIGHT      6
#define SUB_ALIGNMENT_TOPLEFT          7
#define SUB_ALIGNMENT_TOPCENTER        8
#define SUB_ALIGNMENT_TOPRIGHT         9

typedef struct subtitle {

    int lines;

    unsigned long start;
    unsigned long end;

    char *text[SUB_MAX_TEXT];
    unsigned char alignment;
} subtitle;

typedef struct sub_data {
    const char *codec;
    subtitle *subtitles;
    int sub_uses_time;
    int sub_num;          // number of subtitle structs
    int sub_errs;
    double fallback_fps;
} sub_data;

// Parameter struct for the format-specific readline functions
struct readline_args {
    struct mp_log *log;
    int utf16;
    struct MPOpts *opts;

    // subtitle reader state used by some formats

    float mpsub_multiplier;
    float mpsub_position;
    int sub_slacktime;

    int uses_time;

    /*
    Some subtitling formats, namely AQT and Subrip09, define the end of a
    subtitle as the beginning of the following. Since currently we read one
    subtitle at time, for these format we keep two global *subtitle,
    previous_aqt_sub and previous_subrip09_sub, pointing to previous subtitle,
    so we can change its end when we read current subtitle starting time.
    We use a single global unsigned long,
    previous_sub_end, for both (and even future) formats, to store the end of
    the previous sub: it is initialized to 0 in sub_read_file and eventually
    modified by sub_read_aqt_line or sub_read_subrip09_line.
    */
    unsigned long previous_sub_end;
};

/* Maximal length of line of a subtitle */
#define LINE_LEN 1000

static double demux_packet_list_duration(struct demux_packet **pkts, int num_pkts)
{
    if (num_pkts > 0)
        return pkts[num_pkts - 1]->pts + pkts[num_pkts - 1]->duration;
    return 0;
}

static void demux_packet_list_seek(struct demux_packet **pkts, int num_pkts,
                                   int *current, double rel_seek_secs, int flags)
{
    double ref_time = 0;
    if (*current >= 0 && *current < num_pkts) {
        ref_time = pkts[*current]->pts;
    } else if (*current == num_pkts && num_pkts > 0) {
        ref_time = pkts[num_pkts - 1]->pts + pkts[num_pkts - 1]->duration;
    }

    if (flags & SEEK_ABSOLUTE)
        ref_time = 0;

    if (flags & SEEK_FACTOR) {
        ref_time += demux_packet_list_duration(pkts, num_pkts) * rel_seek_secs;
    } else {
        ref_time += rel_seek_secs;
    }

    // Could do binary search, but it's probably not worth the complexity.
    int last_index = 0;
    for (int n = 0; n < num_pkts; n++) {
        if (pkts[n]->pts > ref_time)
            break;
        last_index = n;
    }
    *current = last_index;
}

static struct demux_packet *demux_packet_list_fill(struct demux_packet **pkts,
                                                   int num_pkts, int *current)
{
    if (*current < 0)
        *current = 0;
    if (*current >= num_pkts)
        return NULL;
    struct demux_packet *new = talloc(NULL, struct demux_packet);
    *new = *pkts[*current];
    *current += 1;
    return new;
}

static int eol(char p) {
        return p=='\r' || p=='\n' || p=='\0';
}

static const char *sub_readtext(const char *source, char **dest) {
    int len=0;
    const char *p=source;

//    printf("src=%p  dest=%p  \n",source,dest);

    while ( !eol(*p) && *p!= '|' ) {
        p++,len++;
    }

    *dest= malloc (len+1);
    if (!*dest) {return ERR;}

    strncpy(*dest, source, len);
    (*dest)[len]=0;

    while (*p=='\r' || *p=='\n' || *p=='|') p++;

    if (*p) return p;  // not-last text field
    else return NULL;  // last text field
}

static subtitle *set_multiline_text(struct readline_args *arg, subtitle *current,
                                    const char *text, int start)
{
    int i = start;
    while ((text = sub_readtext(text, current->text + i))) {
        if (current->text[i] == ERR) return ERR;
        i++;
        if (i >= SUB_MAX_TEXT) {
            MP_WARN(arg, "Too many lines in a subtitle\n");
            current->lines = i;
            return current;
        }
    }
    current->lines = i + 1;
    return current;
}

static subtitle *sub_read_line_microdvd(stream_t *st,subtitle *current,
                                        struct readline_args *args)
{
    int utf16 = args->utf16;
    char line[LINE_LEN+1];
    char line2[LINE_LEN+1];

    do {
        if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;
    } while ((sscanf (line,
                      "{%ld}{}%[^\r\n]",
                      &(current->start), line2) < 2) &&
             (sscanf (line,
                      "{%ld}{%ld}%[^\r\n]",
                      &(current->start), &(current->end), line2) < 3));

    return set_multiline_text(args, current, line2, 0);
}

static subtitle *sub_read_line_mpl2(stream_t *st,subtitle *current,
                                    struct readline_args *args)
{
    int utf16 = args->utf16;
    char line[LINE_LEN+1];
    char line2[LINE_LEN+1];

    do {
        if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;
    } while ((sscanf (line,
                      "[%ld][%ld]%[^\r\n]",
                      &(current->start), &(current->end), line2) < 3));
    current->start *= 10;
    current->end *= 10;

    return set_multiline_text(args, current, line2, 0);
}

static subtitle *sub_read_line_subrip(stream_t* st, subtitle *current,
                                    struct readline_args *args)
{
    int utf16 = args->utf16;
    char line[LINE_LEN+1];
    int a1,a2,a3,a4,b1,b2,b3,b4;
    char *p=NULL, *q=NULL;
    int len;

    while (1) {
        if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;
        if (sscanf (line, "%d:%d:%d.%d,%d:%d:%d.%d",&a1,&a2,&a3,&a4,&b1,&b2,&b3,&b4) < 8) continue;
        current->start = a1*360000+a2*6000+a3*100+a4;
        current->end   = b1*360000+b2*6000+b3*100+b4;

        if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;

        p=q=line;
        for (current->lines=1; current->lines < SUB_MAX_TEXT; current->lines++) {
            for (q=p,len=0; *p && *p!='\r' && *p!='\n' && *p!='|' && strncmp(p,"[br]",4); p++,len++);
            current->text[current->lines-1]=malloc (len+1);
            if (!current->text[current->lines-1]) return ERR;
            strncpy (current->text[current->lines-1], q, len);
            current->text[current->lines-1][len]='\0';
            if (!*p || *p=='\r' || *p=='\n') break;
            if (*p=='|') p++;
            else while (*p++!=']');
        }
        break;
    }
    return current;
}

static subtitle *sub_read_line_subviewer(stream_t *st, subtitle *current,
                                         struct readline_args *args)
{
    int utf16 = args->utf16;
    int a1, a2, a3, a4, b1, b2, b3, b4, j = 0;

    while (!current->text[0]) {
        char line[LINE_LEN + 1], full_line[LINE_LEN + 1];
        int i;

        /* Parse SubRip header */
        if (!stream_read_line(st, line, LINE_LEN, utf16))
            return NULL;
        if (sscanf(line, "%d:%d:%d%*1[,.:]%d --> %d:%d:%d%*1[,.:]%d",
                     &a1, &a2, &a3, &a4, &b1, &b2, &b3, &b4) < 8)
            continue;

        current->start = a1 * 360000 + a2 * 6000 + a3 * 100 + a4 / 10;
        current->end   = b1 * 360000 + b2 * 6000 + b3 * 100 + b4 / 10;

        /* Concat lines */
        full_line[0] = 0;
        for (i = 0; i < SUB_MAX_TEXT; i++) {
            int blank = 1, len = 0;
            char *p;

            if (!stream_read_line(st, line, LINE_LEN, utf16))
                break;

            for (p = line; *p != '\n' && *p != '\r' && *p; p++, len++)
                if (*p != ' ' && *p != '\t')
                    blank = 0;

            if (blank)
                break;

            *p = 0;

            if (!(j + 1 + len < sizeof(full_line) - 1))
                break;

            if (j != 0)
                full_line[j++] = '\n';
            snprintf(&full_line[j], sizeof(full_line) - j, "%s", line);
            full_line[LINE_LEN] = '\0';
            j += len;
        }

        if (full_line[0]) {
            current->text[0] = strdup(full_line);
            current->lines = 1;
        }
    }
    return current;
}

static subtitle *sub_read_line_subviewer2(stream_t *st,subtitle *current,
                                          struct readline_args *args)
{
    int utf16 = args->utf16;
    char line[LINE_LEN+1];
    int a1,a2,a3,a4;
    char *p=NULL;
    int i,len;

    while (!current->text[0]) {
        if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;
        if (line[0]!='{')
            continue;
        if ((len=sscanf (line, "{T %d:%d:%d:%d",&a1,&a2,&a3,&a4)) < 4)
            continue;
        current->start = a1*360000+a2*6000+a3*100+a4/10;
        for (i=0; i<SUB_MAX_TEXT;) {
            if (!stream_read_line (st, line, LINE_LEN, utf16)) break;
            if (line[0]=='}') break;
            len=0;
            for (p=line; *p!='\n' && *p!='\r' && *p; ++p,++len);
            if (len) {
                current->text[i]=malloc (len+1);
                if (!current->text[i]) return ERR;
                strncpy (current->text[i], line, len); current->text[i][len]='\0';
                ++i;
            } else {
                break;
            }
        }
        current->lines=i;
    }
    return current;
}

static subtitle *sub_read_line_ssa(stream_t *st,subtitle *current,
                                    struct readline_args *args)
{
    /* Instead of hardcoding the expected fields and their order on
     * each dialogue line, this code should parse the "Format: " line
     * which lists the fields used in the script. As is, this may not
     * work correctly with all scripts.
     */

        int utf16 = args->utf16;
        int comma;

        int hour1, min1, sec1, hunsec1,
            hour2, min2, sec2, hunsec2, nothing;
        int num;

        char line[LINE_LEN+1],
             line3[LINE_LEN+1],
             *line2;
        char *tmp;

        do {
                if (!stream_read_line (st, line, LINE_LEN, utf16)) return NULL;
        } while (sscanf (line, "Dialogue: Marked=%d,%d:%d:%d.%d,%d:%d:%d.%d"
                        "%[^\n\r]", &nothing,
                        &hour1, &min1, &sec1, &hunsec1,
                        &hour2, &min2, &sec2, &hunsec2,
                        line3) < 9
                 &&
                 sscanf (line, "Dialogue: %d,%d:%d:%d.%d,%d:%d:%d.%d"
                         "%[^\n\r]", &nothing,
                         &hour1, &min1, &sec1, &hunsec1,
                         &hour2, &min2, &sec2, &hunsec2,
                         line3) < 9         );

        line2=strchr(line3, ',');
        if (!line2) return NULL;

        for (comma = 3; comma < 9; comma ++)
            if (!(line2 = strchr(++line2, ',')))
                return NULL;
        line2++;

        current->lines=0;num=0;
        current->start = 360000*hour1 + 6000*min1 + 100*sec1 + hunsec1;
        current->end   = 360000*hour2 + 6000*min2 + 100*sec2 + hunsec2;

        while (((tmp=strstr(line2, "\\n")) != NULL) || ((tmp=strstr(line2, "\\N")) != NULL) ){
                current->text[num]=malloc(tmp-line2+1);
                strncpy (current->text[num], line2, tmp-line2);
                current->text[num][tmp-line2]='\0';
                line2=tmp+2;
                num++;
                current->lines++;
                if (current->lines >=  SUB_MAX_TEXT) return current;
        }

        current->text[num]=strdup(line2);
        current->lines++;

        return current;
}

static subtitle *sub_read_line_subrip09(stream_t *st,subtitle *current,
                                    struct readline_args *args)
{
    int utf16 = args->utf16;
    char line[LINE_LEN+1];
    int a1,a2,a3;
    int len;

retry:
    while (1) {
    // try to locate next subtitle
        if (!stream_read_line (st, line, LINE_LEN, utf16))
                return NULL;
        if (!((len=sscanf (line, "[%d:%d:%d]",&a1,&a2,&a3)) < 3))
                break;
    }

    current->start = a1*360000+a2*6000+a3*100;

    if (!args->previous_sub_end)
        args->previous_sub_end = (current->start) ? current->start - 1 : 0;

    if (!stream_read_line (st, line, LINE_LEN, utf16))
        return NULL;

    current->text[0]=""; // just to be sure that string is clear

    if (set_multiline_text(args, current, line, 0) == ERR)
        return ERR;

    if (!strlen(current->text[0]) && current->lines <= 1)
        goto retry;

    return current;
}

static int sub_autodetect (stream_t* st, int *uses_time, int utf16) {
    char line[LINE_LEN+1];
    int i,j=0;

    while (j < 100) {
        j++;
        if (!stream_read_line (st, line, LINE_LEN, utf16))
            return SUB_INVALID;

        if (sscanf (line, "{%d}{%d}", &i, &i)==2)
                {*uses_time=0;return SUB_MICRODVD;}
        if (sscanf (line, "{%d}{}", &i)==1)
                {*uses_time=0;return SUB_MICRODVD;}
        if (sscanf (line, "[%d][%d]", &i, &i)==2)
                {*uses_time=1;return SUB_MPL2;}
        if (sscanf (line, "%d:%d:%d.%d,%d:%d:%d.%d",     &i, &i, &i, &i, &i, &i, &i, &i)==8)
                {*uses_time=1;return SUB_SUBRIP;}
        if (sscanf (line, "%d:%d:%d%*1[,.:]%d --> %d:%d:%d%*1[,.:]%d", &i, &i, &i, &i, &i, &i, &i, &i) == 8)
                {*uses_time=1;return SUB_SUBVIEWER;}
        if (sscanf (line, "{T %d:%d:%d:%d",&i, &i, &i, &i)==4)
                {*uses_time=1;return SUB_SUBVIEWER2;}
        if (!memcmp(line, "Dialogue: Marked", 16))
                {*uses_time=1; return SUB_SSA;}
        if (!memcmp(line, "Dialogue: ", 10))
                {*uses_time=1; return SUB_SSA;}
        if (sscanf (line, "[%d:%d:%d]", &i, &i, &i)==3)
                {*uses_time=1;return SUB_SUBRIP09;}
    }

    return SUB_INVALID;  // too many bad lines
}

struct subreader {
    subtitle * (*read)(stream_t *st, subtitle *dest,
                       struct readline_args *args);
    void       (*post)(subtitle *dest);
    const char *name;
    const char *codec_name;
    struct readline_args args;
};

static void adjust_subs_time(struct subreader *srp, subtitle* sub,
                             float subtime, float fps,
                             float sub_fps, int block,
                             int sub_num, int sub_uses_time) {
        int n,m;
        subtitle* nextsub;
        int i = sub_num;
        unsigned long subfms = (sub_uses_time ? 100 : fps) * subtime;

        n=m=0;
        if (i)  for (;;){
                if (sub->end <= sub->start){
                        sub->end = sub->start + subfms;
                        m++;
                        n++;
                }
                if (!--i) break;
                nextsub = sub + 1;
            if(block){
                if (sub->end >= nextsub->start){
                        sub->end = nextsub->start - 1;
                        if (sub->end - sub->start > subfms)
                                sub->end = sub->start + subfms;
                        if (!m)
                                n++;
                }
            }

                sub = nextsub;
                m = 0;
        }
        if (n) MP_VERBOSE(&srp->args, "Adjusted %d subtitle(s).\n", n);
}

static bool subreader_autodetect(stream_t *fd, struct MPOpts *opts,
                                 struct mp_log *log, struct subreader *out)
{
    static const struct subreader sr[]=
    {
            { sub_read_line_microdvd, NULL, "microdvd", "microdvd" },
            { sub_read_line_subrip, NULL, "subviewer" },
            { sub_read_line_subviewer, NULL, "subrip", "subrip" },
            { sub_read_line_ssa, NULL, "ssa", "ass-text" },
            { sub_read_line_subviewer2, NULL, "subviewer2" },
            { sub_read_line_subrip09, NULL, "subrip9" },
            { sub_read_line_mpl2, NULL, "mpl2" }
    };
    const struct subreader *srp;

    int sub_format = SUB_INVALID;
    int utf16;
    int uses_time = 0;
    for (utf16 = 0; sub_format == SUB_INVALID && utf16 < 3; utf16++) {
        sub_format=sub_autodetect (fd, &uses_time, utf16);
        stream_seek(fd,0);
    }
    utf16--;

    if (sub_format==SUB_INVALID) {
        mp_verbose(log, "Could not determine file format\n");
        return false;
    }
    srp=sr+sub_format;
    mp_verbose(log, "Detected subtitle file format: %s\n", srp->name);

    *out = *srp;
    out->args = (struct readline_args) {
        .log = log,
        .utf16 = utf16,
        .opts = opts,
        .sub_slacktime = 20000, //20 sec
        .mpsub_multiplier = (uses_time ? 100.0 : 1.0),
        .uses_time = uses_time,
    };

    return true;
}

static sub_data* sub_read_file(stream_t *fd, struct subreader *srp)
{
    struct MPOpts *opts = fd->opts;
    float fps = 23.976;
    int n_max, i, j;
    subtitle *first, *sub, *return_sub, *alloced_sub = NULL;
    sub_data *subt_data;
    int sub_num = 0, sub_errs = 0;
    struct readline_args args = srp->args;

    sub_num=0;n_max=32;
    first=malloc(n_max*sizeof(subtitle));
    if (!first)
        abort();

    alloced_sub =
    sub = malloc(sizeof(subtitle));
    //This is to deal with those formats (AQT & Subrip) which define the end of a subtitle
    //as the beginning of the following
    args.previous_sub_end = 0;
    while(1){
        if(sub_num>=n_max){
            n_max+=16;
            first=realloc(first,n_max*sizeof(subtitle));
        }
        memset(sub, '\0', sizeof(subtitle));
        sub=srp->read(fd, sub, &args);
        if(!sub) break;   // EOF

        if ( sub == ERR )
         {
          free(first);
          free(alloced_sub);
          return NULL;
         }
        // Apply any post processing that needs recoding first
        if ((sub!=ERR) && srp->post) srp->post(sub);
        if(!sub_num || (first[sub_num - 1].start <= sub->start)){
            first[sub_num].start = sub->start;
            first[sub_num].end   = sub->end;
            first[sub_num].lines = sub->lines;
            first[sub_num].alignment = sub->alignment;
            for(i = 0; i < sub->lines; ++i){
                first[sub_num].text[i] = sub->text[i];
            }
            if (args.previous_sub_end){
                first[sub_num - 1].end = args.previous_sub_end;
                args.previous_sub_end = 0;
            }
        } else {
            for(j = sub_num - 1; j >= 0; --j){
                first[j + 1].start = first[j].start;
                first[j + 1].end   = first[j].end;
                first[j + 1].lines = first[j].lines;
                first[j + 1].alignment = first[j].alignment;
                for(i = 0; i < first[j].lines; ++i){
                    first[j + 1].text[i] = first[j].text[i];
                }
                if(!j || (first[j - 1].start <= sub->start)){
                    first[j].start = sub->start;
                    first[j].end   = sub->end;
                    first[j].lines = sub->lines;
                    first[j].alignment = sub->alignment;
                    for(i = 0; i < SUB_MAX_TEXT; ++i){
                        first[j].text[i] = sub->text[i];
                    }
                    if (args.previous_sub_end){
                        first[j].end = first[j - 1].end;
                        first[j - 1].end = args.previous_sub_end;
                        args.previous_sub_end = 0;
                    }
                    break;
                }
            }
        }
        if(sub==ERR) ++sub_errs; else ++sub_num; // Error vs. Valid
    }

    free(alloced_sub);

//    printf ("Subtitle format %s time.\n", uses_time?"uses":"doesn't use");
    MP_VERBOSE(&srp->args, "Read %i subtitles, %i bad line(s).\n",
           sub_num, sub_errs);

    if(sub_num<=0){
        free(first);
        return NULL;
    }

    adjust_subs_time(srp, first, 6.0, fps, opts->sub_fps, 1, sub_num, args.uses_time);/*~6 secs AST*/
    return_sub = first;

    if (return_sub == NULL) return NULL;
    subt_data = talloc_zero(NULL, sub_data);
    subt_data->codec = srp->codec_name ? srp->codec_name : "text";
    subt_data->sub_uses_time = args.uses_time;
    subt_data->sub_num = sub_num;
    subt_data->sub_errs = sub_errs;
    subt_data->subtitles = return_sub;
    subt_data->fallback_fps = fps;
    return subt_data;
}

static void subdata_free(sub_data *subd)
{
    int i, j;
    for (i = 0; i < subd->sub_num; i++)
        for (j = 0; j < subd->subtitles[i].lines; j++)
            free( subd->subtitles[i].text[j] );
    free( subd->subtitles );
    talloc_free(subd);
}

struct priv {
    struct demux_packet **pkts;
    int num_pkts;
    int current;
    struct sh_stream *sh;
};

static void add_sub_data(struct demuxer *demuxer, struct sub_data *subdata)
{
    struct priv *priv = demuxer->priv;

    for (int i = 0; i < subdata->sub_num; i++) {
        subtitle *st = &subdata->subtitles[i];
        // subdata is in 10 ms ticks, pts is in seconds
        double t = subdata->sub_uses_time ? 0.01 : (1 / subdata->fallback_fps);

        int len = 0;
        for (int j = 0; j < st->lines; j++)
            len += st->text[j] ? strlen(st->text[j]) : 0;

        len += 2 * st->lines;   // '\N', including the one after the last line
        len += 6;               // {\anX}
        len += 1;               // '\0'

        char *data = talloc_array(NULL, char, len);

        char *p = data;
        char *end = p + len;

        if (st->alignment)
            p += snprintf(p, end - p, "{\\an%d}", st->alignment);

        for (int j = 0; j < st->lines; j++)
            p += snprintf(p, end - p, "%s\\N", st->text[j]);

        if (st->lines > 0)
            p -= 2;             // remove last "\N"
        *p = 0;

        struct demux_packet *pkt = talloc_ptrtype(priv, pkt);
        *pkt = (struct demux_packet) {
            .pts = st->start * t,
            .duration = (st->end - st->start) * t,
            .buffer = talloc_steal(pkt, data),
            .len = strlen(data),
        };

        MP_TARRAY_APPEND(priv, priv->pkts, priv->num_pkts, pkt);
    }
}

static struct stream *read_probe_stream(struct stream *s, int max)
{
    // Very roundabout, but only needed for initial probing.
    bstr probe = stream_peek(s, max);
    return open_memory_stream(probe.start, probe.len);
}

#define PROBE_SIZE FFMIN(32 * 1024, STREAM_MAX_BUFFER_SIZE)

static int d_open_file(struct demuxer *demuxer, enum demux_check check)
{
    if (check > DEMUX_CHECK_REQUEST)
        return -1;

    if (!demuxer->params || !demuxer->params->expect_subtitle)
        return -1;

    struct stream *ps = read_probe_stream(demuxer->stream, PROBE_SIZE);

    struct subreader sr;
    bool res = subreader_autodetect(ps, demuxer->opts, demuxer->log, &sr);

    free_stream(ps);

    if (!res)
        return -1;

    demuxer->filetype = sr.name;

    sub_data *sd = sub_read_file(demuxer->stream, &sr);
    if (!sd)
        return -1;

    struct priv *p = talloc_zero(demuxer, struct priv);
    demuxer->priv = p;

    p->sh = new_sh_stream(demuxer, STREAM_SUB);
    p->sh->codec = sd->codec;
    p->sh->sub->frame_based = sd->sub_uses_time ? 0 : 23.976;
    p->sh->sub->is_utf8 = sr.args.utf16 != 0; // converted from utf-16 -> utf-8

    add_sub_data(demuxer, sd);
    subdata_free(sd);

    demuxer->seekable = true;
    demuxer->fully_read = true;

    return 0;
}

static int d_fill_buffer(struct demuxer *demuxer)
{
    struct priv *p = demuxer->priv;
    struct demux_packet *dp = demux_packet_list_fill(p->pkts, p->num_pkts,
                                                     &p->current);
    return demux_add_packet(p->sh, dp);
}

static void d_seek(struct demuxer *demuxer, double secs, int flags)
{
    struct priv *p = demuxer->priv;
    demux_packet_list_seek(p->pkts, p->num_pkts, &p->current, secs, flags);
}

static int d_control(struct demuxer *demuxer, int cmd, void *arg)
{
    struct priv *p = demuxer->priv;
    switch (cmd) {
    case DEMUXER_CTRL_GET_TIME_LENGTH:
        *((double *) arg) = demux_packet_list_duration(p->pkts, p->num_pkts);
        return DEMUXER_CTRL_OK;
    default:
        return DEMUXER_CTRL_NOTIMPL;
    }
}

const struct demuxer_desc demuxer_desc_subreader = {
    .name = "subreader",
    .desc = "Deprecated MPlayer subreader",
    .open = d_open_file,
    .fill_buffer = d_fill_buffer,
    .seek = d_seek,
    .control = d_control,
};