ffmpeg/libavformat/jacosubdec.c

/*
 * Copyright (c) 2012 Clément Bœsch
 *
 * 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
 */

/**
 * @file
 * JACOsub subtitle demuxer
 * @see http://unicorn.us.com/jacosub/jscripts.html
 * @todo Support P[ALETTE] directive.
 */

#include "avformat.h"
#include "internal.h"
#include "libavcodec/jacosub.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
#include "libavutil/intreadwrite.h"

typedef struct {
    char *line;         ///< null-terminated heap allocated subtitle line
    int64_t pos;        ///< offset position
    int start;          ///< timestamp start
    int end;            ///< timestamp end
} SubEntry;

typedef struct {
    int shift;
    unsigned timeres;
    SubEntry *subs;     ///< subtitles list
    int nsub;           ///< number of subtitles
    int sid;            ///< current subtitle
} JACOsubContext;

static int timed_line(const char *ptr)
{
    char c;
    return (sscanf(ptr, "%*u:%*u:%*u.%*u %*u:%*u:%*u.%*u %c", &c) == 1 ||
            sscanf(ptr, "@%*u @%*u %c",                       &c) == 1);
}

static int jacosub_probe(AVProbeData *p)
{
    const char *ptr     = p->buf;
    const char *ptr_end = p->buf + p->buf_size;

    if (AV_RB24(ptr) == 0xEFBBBF)
        ptr += 3; /* skip UTF-8 BOM */

    while (ptr < ptr_end) {
        if (timed_line(ptr))
            return AVPROBE_SCORE_MAX / 2;
        while (jss_whitespace(*ptr))
            ptr++;
        ptr += strcspn(ptr, "\n") + 1;
    }
    return 0;
}

static const char * const cmds[] = {
    "CLOCKPAUSE",
    "DIRECTIVE",
    "FONT",
    "HRES",
    "INCLUDE",
    "PALETTE",
    "QUANTIZE",
    "RAMP",
    "SHIFT",
    "TIMERES",
};

static int get_jss_cmd(char k)
{
    int i;

    k = av_toupper(k);
    for (i = 0; i < FF_ARRAY_ELEMS(cmds); i++)
        if (k == cmds[i][0])
            return i;
    return -1;
}

static int jacosub_read_close(AVFormatContext *s)
{
    int i;
    JACOsubContext *jacosub = s->priv_data;

    for (i = 0; i < jacosub->nsub; i++)
        av_freep(&jacosub->subs[i].line);
    jacosub->nsub = 0;
    av_freep(&jacosub->subs);
    return 0;
}

static const char *read_ts(JACOsubContext *jacosub, const char *buf,
                           int *ts_start, int *ts_end)
{
    int len;
    unsigned hs, ms, ss, fs; // hours, minutes, seconds, frame start
    unsigned he, me, se, fe; // hours, minutes, seconds, frame end

    /* timed format */
    if (sscanf(buf, "%u:%u:%u.%u %u:%u:%u.%u %n",
               &hs, &ms, &ss, &fs,
               &he, &me, &se, &fe, &len) == 8) {
        *ts_start = (hs*3600 + ms*60 + ss) * jacosub->timeres + fs;
        *ts_end   = (he*3600 + me*60 + se) * jacosub->timeres + fe;
        goto shift_and_ret;
    }

    /* timestamps format */
    if (sscanf(buf, "@%u @%u %n", ts_start, ts_end, &len) == 2)
        goto shift_and_ret;

    return NULL;

shift_and_ret:
    *ts_start = (*ts_start + jacosub->shift) * 100 / jacosub->timeres;
    *ts_end   = (*ts_end   + jacosub->shift) * 100 / jacosub->timeres;
    return buf + len;
}

static int get_shift(int timeres, const char *buf)
{
    int sign = 1;
    int a = 0, b = 0, c = 0, d = 0;
#define SSEP "%*1[.:]"
    int n = sscanf(buf, "%d"SSEP"%d"SSEP"%d"SSEP"%d", &a, &b, &c, &d);
#undef SSEP

    if (*buf == '-' || a < 0) {
        sign = -1;
        a = FFABS(a);
    }

    switch (n) {
    case 4: return sign * ((a*3600 + b*60 + c) * timeres + d);
    case 3: return sign * ((         a*60 + b) * timeres + c);
    case 2: return sign * ((                a) * timeres + b);
    }

    return 0;
}

static int cmp_timed_sub(const void *a, const void *b)
{
    return ((const SubEntry*)a)->start - ((const SubEntry*)b)->start;
}

static int jacosub_read_header(AVFormatContext *s)
{
    AVBPrint header;
    AVIOContext *pb = s->pb;
    char line[JSS_MAX_LINESIZE];
    JACOsubContext *jacosub = s->priv_data;
    int shift_set = 0; // only the first shift matters
    int merge_line = 0;
    int i;

    AVStream *st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);
    avpriv_set_pts_info(st, 64, 1, 100);
    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
    st->codec->codec_id   = CODEC_ID_JACOSUB;

    jacosub->timeres = 30;

    av_bprint_init(&header, 1024+FF_INPUT_BUFFER_PADDING_SIZE, 4096);

    while (!url_feof(pb)) {
        int cmd_len;
        const char *p = line;
        int64_t pos = avio_tell(pb);

        ff_get_line(pb, line, sizeof(line));

        p = jss_skip_whitespace(p);

        /* queue timed line */
        if (merge_line || timed_line(p)) {
            SubEntry *subs, *sub;
            const int len = strlen(line);

            if (merge_line) {
                char *tmp;
                const int old_len = strlen(sub->line);

                sub = &subs[jacosub->nsub];
                tmp = av_realloc(sub->line, old_len + len + 1);
                if (!tmp)
                    return AVERROR(ENOMEM);
                sub->line = tmp;
                strcpy(sub->line + old_len, line);
            } else {
                subs = av_realloc(jacosub->subs,
                                  sizeof(*jacosub->subs) * (jacosub->nsub+1));
                if (!subs)
                    return AVERROR(ENOMEM);
                jacosub->subs = subs;
                sub = &subs[jacosub->nsub];
                sub->pos  = pos;
                sub->line = av_strdup(line);
                if (!sub->line)
                    return AVERROR(ENOMEM);
            }
            merge_line = len > 1 && !strcmp(&line[len - 2], "\\\n");
            if (!merge_line)
                jacosub->nsub++;
            continue;
        }

        /* skip all non-compiler commands and focus on the command */
        if (*p != '#')
            continue;
        p++;
        i = get_jss_cmd(p[0]);
        if (i == -1)
            continue;

        /* trim command + spaces */
        cmd_len = strlen(cmds[i]);
        if (av_strncasecmp(p, cmds[i], cmd_len) == 0)
            p += cmd_len;
        else
            p++;
        p = jss_skip_whitespace(p);

        /* handle commands which affect the whole script */
        switch (cmds[i][0]) {
        case 'S': // SHIFT command affect the whole script...
            if (!shift_set) {
                jacosub->shift = get_shift(jacosub->timeres, p);
                shift_set = 1;
            }
            av_bprintf(&header, "#S %s", p);
            break;
        case 'T': // ...but must be placed after TIMERES
            jacosub->timeres = strtol(p, NULL, 10);
            av_bprintf(&header, "#T %s", p);
            break;
        }
    }

    /* general/essential directives in the extradata */
    av_bprint_finalize(&header, (char **)&st->codec->extradata);
    st->codec->extradata_size = header.len + 1;

    /* SHIFT and TIMERES affect the whole script so packet timing can only be
     * done in a second pass */
    for (i = 0; i < jacosub->nsub; i++) {
        SubEntry *sub = &jacosub->subs[i];
        read_ts(jacosub, sub->line, &sub->start, &sub->end);
    }
    qsort(jacosub->subs, jacosub->nsub, sizeof(*jacosub->subs), cmp_timed_sub);

    return 0;
}

static int jacosub_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    int res;
    JACOsubContext *jacosub = s->priv_data;
    const SubEntry *sub = &jacosub->subs[jacosub->sid++];

    if (jacosub->sid == jacosub->nsub)
        return AVERROR_EOF;
    res = av_new_packet(pkt, strlen(sub->line));
    if (res)
        return res;
    strcpy(pkt->data, sub->line);
    pkt->flags |= AV_PKT_FLAG_KEY;
    pkt->pos = sub->pos;
    pkt->pts = pkt->dts = sub->start;
    pkt->duration = sub->end - sub->start;
    return 0;
}

AVInputFormat ff_jacosub_demuxer = {
    .name           = "jacosub",
    .long_name      = NULL_IF_CONFIG_SMALL("JACOsub subtitle format"),
    .priv_data_size = sizeof(JACOsubContext),
    .read_probe     = jacosub_probe,
    .read_header    = jacosub_read_header,
    .read_packet    = jacosub_read_packet,
    .read_close     = jacosub_read_close,
    .flags          = AVFMT_GENERIC_INDEX,
};