FFmpeg/libavformat/microdvddec.c

/*
 * MicroDVD subtitle demuxer
 * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>
 * Copyright (c) 2012  Clément Bœsch <ubitux@gmail.com>
 *
 * 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 "avformat.h"
#include "internal.h"
#include "subtitles.h"
#include "libavutil/intreadwrite.h"

#define MAX_LINESIZE 2048


typedef struct {
    FFDemuxSubtitlesQueue q;
} MicroDVDContext;


static int microdvd_probe(AVProbeData *p)
{
    unsigned char c, *ptr = p->buf;
    int i;

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

    for (i=0; i<3; i++) {
        if (sscanf(ptr, "{%*d}{}%c",     &c) != 1 &&
            sscanf(ptr, "{%*d}{%*d}%c",  &c) != 1 &&
            sscanf(ptr, "{DEFAULT}{}%c", &c) != 1)
            return 0;
        ptr += strcspn(ptr, "\n") + 1;
    }
    return AVPROBE_SCORE_MAX;
}

static int64_t get_pts(const char *buf)
{
    int frame;
    char c;

    if (sscanf(buf, "{%d}{%c", &frame, &c) == 2)
        return frame;
    return AV_NOPTS_VALUE;
}

static int get_duration(const char *buf)
{
    int frame_start, frame_end;

    if (sscanf(buf, "{%d}{%d}", &frame_start, &frame_end) == 2)
        return frame_end - frame_start;
    return -1;
}

static int microdvd_read_header(AVFormatContext *s)
{
    AVRational pts_info = (AVRational){ 2997, 125 };  /* default: 23.976 fps */
    MicroDVDContext *microdvd = s->priv_data;
    AVStream *st = avformat_new_stream(s, NULL);
    int i = 0;
    char line[MAX_LINESIZE];

    if (!st)
        return AVERROR(ENOMEM);

    while (!url_feof(s->pb)) {
        AVPacket *sub;
        int64_t pos = avio_tell(s->pb);
        int len = ff_get_line(s->pb, line, sizeof(line));

        if (!len)
            break;
        if (i < 3) {
            int frame;
            double fps;
            char c;

            i++;
            if ((sscanf(line, "{%d}{}%6lf",    &frame, &fps) == 2 ||
                 sscanf(line, "{%d}{%*d}%6lf", &frame, &fps) == 2)
                && frame <= 1 && fps > 3 && fps < 100)
                pts_info = av_d2q(fps, 100000);
            if (!st->codec->extradata && sscanf(line, "{DEFAULT}{}%c", &c) == 1) {
                st->codec->extradata = av_strdup(line + 11);
                if (!st->codec->extradata)
                    return AVERROR(ENOMEM);
                st->codec->extradata_size = strlen(st->codec->extradata) + 1;
                continue;
            }
        }
        sub = ff_subtitles_queue_insert(&microdvd->q, line, len, 0);
        if (!sub)
            return AVERROR(ENOMEM);
        sub->pos = pos;
        sub->pts = get_pts(sub->data);
        sub->duration = get_duration(sub->data);
    }
    ff_subtitles_queue_finalize(&microdvd->q);
    avpriv_set_pts_info(st, 64, pts_info.den, pts_info.num);
    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
    st->codec->codec_id   = AV_CODEC_ID_MICRODVD;
    return 0;
}

static int microdvd_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    MicroDVDContext *microdvd = s->priv_data;
    return ff_subtitles_queue_read_packet(&microdvd->q, pkt);
}

static int microdvd_read_close(AVFormatContext *s)
{
    MicroDVDContext *microdvd = s->priv_data;
    ff_subtitles_queue_clean(&microdvd->q);
    return 0;
}

AVInputFormat ff_microdvd_demuxer = {
    .name           = "microdvd",
    .long_name      = NULL_IF_CONFIG_SMALL("MicroDVD subtitle format"),
    .priv_data_size = sizeof(MicroDVDContext),
    .read_probe     = microdvd_probe,
    .read_header    = microdvd_read_header,
    .read_packet    = microdvd_read_packet,
    .read_close     = microdvd_read_close,
    .flags          = AVFMT_GENERIC_INDEX,
};