libavformat/sccdec.c

   1 /*
   2  * SCC subtitle demuxer
   3  * Copyright (c) 2017 Paul B Mahol
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "avformat.h"
  23 #include "demux.h"
  24 #include "internal.h"
  25 #include "subtitles.h"
  26 #include "libavutil/avstring.h"
  27 #include "libavutil/intreadwrite.h"
  28
  29 typedef struct SCCContext {
  30     FFDemuxSubtitlesQueue q;
  31 } SCCContext;
  32
  33 static int scc_probe(const AVProbeData *p)
  34 {
  35     char buf[18];
  36     FFTextReader tr;
  37
  38     ff_text_init_buf(&tr, p->buf, p->buf_size);
  39
  40     while (ff_text_peek_r8(&tr) == '\r' || ff_text_peek_r8(&tr) == '\n')
  41         ff_text_r8(&tr);
  42
  43     ff_text_read(&tr, buf, sizeof(buf));
  44
  45     if (!memcmp(buf, "Scenarist_SCC V1.0", 18))
  46         return AVPROBE_SCORE_MAX;
  47
  48     return 0;
  49 }
  50
  51 static int convert(uint8_t x)
  52 {
  53     if (x >= 'a')
  54         x -= 'a' - 10;
  55     else if (x >= 'A')
  56         x -= 'A' - 10;
  57     else
  58         x -= '0';
  59     return x;
  60 }
  61
  62 static int scc_read_header(AVFormatContext *s)
  63 {
  64     SCCContext *scc = s->priv_data;
  65     AVStream *st = avformat_new_stream(s, NULL);
  66     AVPacket *sub = NULL;
  67     ptrdiff_t len;
  68     uint8_t out[4096];
  69     FFTextReader tr;
  70
  71     ff_text_init_avio(s, &tr, s->pb);
  72
  73     if (!st)
  74         return AVERROR(ENOMEM);
  75     avpriv_set_pts_info(st, 64, 1, 1000);
  76     st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
  77     st->codecpar->codec_id   = AV_CODEC_ID_EIA_608;
  78
  79     while (1) {
  80         char *saveptr = NULL, *lline;
  81         int hh, mm, ss, fs, i;
  82         char line[4096];
  83         int64_t pos, ts;
  84
  85         pos = ff_text_pos(&tr);
  86         len = ff_subtitles_read_line(&tr, line, sizeof(line));
  87         if (len <= 13) {
  88             if (ff_text_eof(&tr))
  89                 break;
  90             continue;
  91         }
  92         if (av_sscanf(line, "%d:%d:%d%*[:;]%d", &hh, &mm, &ss, &fs) != 4)
  93             continue;
  94
  95         ts = (hh * 3600LL + mm * 60LL + ss) * 1000LL + fs * 33LL;
  96         if (sub)
  97             sub->duration = ts - sub->pts;
  98
  99         lline  = line;
 100         lline += 12;
 101
 102         for (i = 0; i < 4095; i += 3) {
 103             char *ptr = av_strtok(lline, " ", &saveptr);
 104             char c1, c2, c3, c4;
 105             uint8_t o1, o2;
 106
 107             if (!ptr)
 108                 break;
 109
 110             if (av_sscanf(ptr, "%c%c%c%c", &c1, &c2, &c3, &c4) != 4)
 111                 break;
 112             o1 = convert(c2) | (convert(c1) << 4);
 113             o2 = convert(c4) | (convert(c3) << 4);
 114
 115             lline = NULL;
 116
 117             if (i > 12 && o1 == 0x94 && o2 == 0x20 && saveptr &&
 118                 (av_strncasecmp(saveptr, "942f", 4) && !av_strncasecmp(saveptr, "942c", 4))) {
 119
 120                 sub = ff_subtitles_queue_insert(&scc->q, out, i, 0);
 121                 if (!sub)
 122                     return AVERROR(ENOMEM);
 123
 124                 sub->pos = pos;
 125                 pos += i;
 126                 sub->pts = ts;
 127                 sub->duration = i * 11;
 128                 ts += sub->duration;
 129                 i = 0;
 130             }
 131
 132             out[i+0] = 0xfc;
 133             out[i+1] = o1;
 134             out[i+2] = o2;
 135         }
 136
 137         sub = ff_subtitles_queue_insert(&scc->q, out, i, 0);
 138         if (!sub)
 139             return AVERROR(ENOMEM);
 140
 141         sub->pos = pos;
 142         sub->pts = ts;
 143     }
 144
 145     ff_subtitles_queue_finalize(s, &scc->q);
 146
 147     return 0;
 148 }
 149
 150 const FFInputFormat ff_scc_demuxer = {
 151     .p.name         = "scc",
 152     .p.long_name    = NULL_IF_CONFIG_SMALL("Scenarist Closed Captions"),
 153     .p.extensions   = "scc",
 154     .priv_data_size = sizeof(SCCContext),
 155     .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
 156     .read_probe     = scc_probe,
 157     .read_header    = scc_read_header,
 158     .read_packet    = ff_subtitles_read_packet,
 159     .read_seek2     = ff_subtitles_read_seek,
 160     .read_close     = ff_subtitles_read_close,
 161 };