mpsubdec.c

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/*
 * 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
 * MPlayer subtitles format demuxer
 */
 
#include "avformat.h"
#include "demux.h"
#include "internal.h"
#include "subtitles.h"
 
#define TSBASE 10000000
 
typedef struct {
    FFDemuxSubtitlesQueue q;
} MPSubContext;
 
static int mpsub_probe(const AVProbeData *p)
{
    const char *ptr     = p->buf;
    const char *ptr_end = p->buf + p->buf_size;
 
    while (ptr < ptr_end) {
        int inc;
 
        if (!memcmp(ptr, "FORMAT=TIME", 11))
            return AVPROBE_SCORE_EXTENSION;
        if (!memcmp(ptr, "FORMAT=", 7))
            return AVPROBE_SCORE_EXTENSION / 3;
        inc = ff_subtitles_next_line(ptr);
        if (!inc)
            break;
        ptr += inc;
    }
    return 0;
}
 
static int parse_line(const char *line, int64_t *value, int64_t *value2)
{
    int vi, p1, p2;
 
    for (vi = 0; vi < 2; vi++) {
        long long intval, fracval;
        int n = av_sscanf(line, "%lld%n.%lld%n", &intval, &p1, &fracval, &p2);
        if (n <= 0 || intval < INT64_MIN / TSBASE || intval > INT64_MAX / TSBASE)
            return AVERROR_INVALIDDATA;
 
        intval *= TSBASE;
 
        if (n == 2) {
            if (fracval < 0)
                return AVERROR_INVALIDDATA;
            for (;p2 - p1 < 7 + 1; p1--)
                fracval *= 10;
            for (;p2 - p1 > 7 + 1; p1++)
                fracval /= 10;
            if (intval > 0) intval = av_sat_add64(intval, fracval);
            else            intval = av_sat_sub64(intval, fracval);
            line += p2;
        } else
            line += p1;
 
        *value = intval;
 
        value = value2;
    }
 
    return 0;
}
 
static int mpsub_read_header(AVFormatContext *s)
{
    MPSubContext *mpsub = s->priv_data;
    AVStream *st;
    AVBPrint buf;
    AVRational pts_info = (AVRational){ TSBASE, 1 }; // ts based by default
    int res = 0;
    int64_t current_pts = 0;
    int i;
    int common_factor = 0;
 
    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
 
    while (!avio_feof(s->pb)) {
        char line[1024];
        int64_t start, duration;
        int fps, len = ff_get_line(s->pb, line, sizeof(line));
 
        if (!len)
            break;
 
        line[strcspn(line, "\r\n")] = 0;
 
        if (sscanf(line, "FORMAT=%d", &fps) == 1 && fps > 3 && fps < 100) {
            /* frame based timing */
            pts_info = (AVRational){ TSBASE * fps, 1 };
        } else if (parse_line(line, &start, &duration) >= 0) {
            AVPacket *sub;
            const int64_t pos = avio_tell(s->pb);
 
            res = ff_subtitles_read_chunk(s->pb, &buf);
            if (res < 0) goto end;
            if (buf.len) {
                sub = ff_subtitles_queue_insert_bprint(&mpsub->q, &buf, 0);
                if (!sub) {
                    res = AVERROR(ENOMEM);
                    goto end;
                }
                if (   current_pts < 0 && start < INT64_MIN - current_pts
                    || current_pts > 0 && start > INT64_MAX - current_pts) {
                    res = AVERROR_INVALIDDATA;
                    goto end;
                }
                sub->pts = current_pts + start;
                if (duration < 0 || sub->pts > INT64_MAX - duration) {
                    res = AVERROR_INVALIDDATA;
                    goto end;
                }
                sub->duration = duration;
 
                common_factor = av_gcd(duration, common_factor);
                common_factor = av_gcd(sub->pts, common_factor);
 
                current_pts = sub->pts + duration;
                sub->pos = pos;
            }
        }
    }
 
    if (common_factor > 1) {
        common_factor = av_gcd(pts_info.num, common_factor);
        for (i = 0; i < mpsub->q.nb_subs; i++) {
            mpsub->q.subs[i]->pts      /= common_factor;
            mpsub->q.subs[i]->duration /= common_factor;
        }
        pts_info.num /= common_factor;
    }
 
    st = avformat_new_stream(s, NULL);
    if (!st) {
        res = AVERROR(ENOMEM);
        goto end;
    }
    avpriv_set_pts_info(st, 64, pts_info.den, pts_info.num);
    st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
    st->codecpar->codec_id   = AV_CODEC_ID_TEXT;
 
    ff_subtitles_queue_finalize(s, &mpsub->q);
 
end:
    av_bprint_finalize(&buf, NULL);
    return res;
}
 
const FFInputFormat ff_mpsub_demuxer = {
    .p.name         = "mpsub",
    .p.long_name    = NULL_IF_CONFIG_SMALL("MPlayer subtitles"),
    .p.extensions   = "sub",
    .priv_data_size = sizeof(MPSubContext),
    .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
    .read_probe     = mpsub_probe,
    .read_header    = mpsub_read_header,
    .read_packet    = ff_subtitles_read_packet,
    .read_seek2     = ff_subtitles_read_seek,
    .read_close     = ff_subtitles_read_close,
};