PeerStreamer

/*

 * SSA/ASS demuxer

 * Copyright (c) 2008 Michael Niedermayer

 *

 * This file is part of Libav.

 *

 * Libav 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.

 *

 * Libav 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 Libav; 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"

#define MAX_LINESIZE 2000

typedef struct ASSContext{

    uint8_t *event_buffer;

    uint8_t **event;

    unsigned int event_count;

    unsigned int event_index;

}ASSContext;

static int probe(AVProbeData *p)

{

    const char *header= "[Script Info]";

    if(   !memcmp(p->buf  , header, strlen(header))

       || !memcmp(p->buf+3, header, strlen(header)))

        return AVPROBE_SCORE_MAX;

    return 0;

}

static int read_close(AVFormatContext *s)

{

    ASSContext *ass = s->priv_data;

    av_freep(&ass->event_buffer);

    av_freep(&ass->event);

    return 0;

}

static int64_t get_pts(const uint8_t *p)

{

    int hour, min, sec, hsec;

    if(sscanf(p, "%*[^,],%d:%d:%d%*c%d", &hour, &min, &sec, &hsec) != 4)

        return AV_NOPTS_VALUE;

//    av_log(NULL, AV_LOG_ERROR, "%d %d %d %d %d [%s]\n", i, hour, min, sec, hsec, p);

    min+= 60*hour;

    sec+= 60*min;

    return sec*100+hsec;

}

static int event_cmp(uint8_t **a, uint8_t **b)

{

    return get_pts(*a) - get_pts(*b);

}

static int read_header(AVFormatContext *s, AVFormatParameters *ap)

{

    int i, len, header_remaining;

    ASSContext *ass = s->priv_data;

    AVIOContext *pb = s->pb;

    AVStream *st;

    int allocated[2]={0};

    uint8_t *p, **dst[2]={0};

    int pos[2]={0};

    st = av_new_stream(s, 0);

    if (!st)

        return -1;

    av_set_pts_info(st, 64, 1, 100);

    st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;

    st->codec->codec_id= CODEC_ID_SSA;

    header_remaining= INT_MAX;

    dst[0] = &st->codec->extradata;

    dst[1] = &ass->event_buffer;

    while(!pb->eof_reached){

        uint8_t line[MAX_LINESIZE];

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

        if(!memcmp(line, "[Events]", 8))

            header_remaining= 2;

        else if(line[0]=='[')

            header_remaining= INT_MAX;

        i= header_remaining==0;

        if(i && get_pts(line) == AV_NOPTS_VALUE)

            continue;

        p = av_fast_realloc(*(dst[i]), &allocated[i], pos[i]+MAX_LINESIZE);

        if(!p)

            goto fail;

        *(dst[i])= p;

        memcpy(p + pos[i], line, len+1);

        pos[i] += len;

        if(i) ass->event_count++;

        else  header_remaining--;

    }

    st->codec->extradata_size= pos[0];

    if(ass->event_count >= UINT_MAX / sizeof(*ass->event))

        goto fail;

    ass->event= av_malloc(ass->event_count * sizeof(*ass->event));

    p= ass->event_buffer;

    for(i=0; i<ass->event_count; i++){

        ass->event[i]= p;

        while(*p && *p != '\n')

            p++;

        p++;

    }

    qsort(ass->event, ass->event_count, sizeof(*ass->event), (void*)event_cmp);

    return 0;

fail:

    read_close(s);

    return -1;

}

static int read_packet(AVFormatContext *s, AVPacket *pkt)

{

    ASSContext *ass = s->priv_data;

    uint8_t *p, *end;

    if(ass->event_index >= ass->event_count)

        return AVERROR(EIO);

    p= ass->event[ ass->event_index ];

    end= strchr(p, '\n');

    av_new_packet(pkt, end ? end-p+1 : strlen(p));

    pkt->flags |= AV_PKT_FLAG_KEY;

    pkt->pos= p - ass->event_buffer + s->streams[0]->codec->extradata_size;

    pkt->pts= pkt->dts= get_pts(p);

    memcpy(pkt->data, p, pkt->size);

    ass->event_index++;

    return 0;

}

static int read_seek2(AVFormatContext *s, int stream_index,

                      int64_t min_ts, int64_t ts, int64_t max_ts, int flags)

{

    ASSContext *ass = s->priv_data;

    if (flags & AVSEEK_FLAG_BYTE) {

        return AVERROR_NOTSUPP;

    } else if (flags & AVSEEK_FLAG_FRAME) {

        if (ts < 0 || ts >= ass->event_count)

            return AVERROR(ERANGE);

        ass->event_index = ts;

    } else {

        int i, idx = -1;

        int64_t min_ts_diff = INT64_MAX;

        if (stream_index == -1) {

            AVRational time_base = s->streams[0]->time_base;

            ts = av_rescale_q(ts, AV_TIME_BASE_Q, time_base);

            min_ts = av_rescale_rnd(min_ts, time_base.den,

                                    time_base.num * (int64_t)AV_TIME_BASE,

                                    AV_ROUND_UP);

            max_ts = av_rescale_rnd(max_ts, time_base.den,

                                    time_base.num * (int64_t)AV_TIME_BASE,

                                    AV_ROUND_DOWN);

        }

        /* TODO: ass->event[] is sorted by pts so we could do a binary search */

        for (i=0; i<ass->event_count; i++) {

            int64_t pts = get_pts(ass->event[i]);

            int64_t ts_diff = FFABS(pts - ts);

            if (pts >= min_ts && pts <= max_ts && ts_diff < min_ts_diff) {

                min_ts_diff = ts_diff;

                idx = i;

            }

        }

        if (idx < 0)

            return AVERROR(ERANGE);

        ass->event_index = idx;

    }

    return 0;

}

AVInputFormat ff_ass_demuxer = {

    .name           = "ass",

    .long_name      = NULL_IF_CONFIG_SMALL("Advanced SubStation Alpha subtitle format"),

    .priv_data_size = sizeof(ASSContext),

    .read_probe     = probe,

    .read_header    = read_header,

    .read_packet    = read_packet,

    .read_close     = read_close,

    .read_seek2     = read_seek2,

};