libavcodec/xsubdec.c

   1 /*
   2  * XSUB subtitle decoder
   3  * Copyright (c) 2007 Reimar Döffinger
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "libavutil/mathematics.h"
  23 #include "libavutil/imgutils.h"
  24 #include "avcodec.h"
  25 #include "get_bits.h"
  26 #include "bytestream.h"
  27
  28 static av_cold int decode_init(AVCodecContext *avctx) {
  29     avctx->pix_fmt = AV_PIX_FMT_PAL8;
  30     return 0;
  31 }
  32
  33 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
  34 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
  35
  36 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
  37     int i;
  38     int64_t ms = 0;
  39     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
  40         return AV_NOPTS_VALUE;
  41     for (i = 0; i < sizeof(tc_offsets); i++) {
  42         uint8_t c = buf[tc_offsets[i]] - '0';
  43         if (c > 9) return AV_NOPTS_VALUE;
  44         ms = (ms + c) * tc_muls[i];
  45     }
  46     return ms - packet_time;
  47 }
  48
  49 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
  50                         AVPacket *avpkt) {
  51     const uint8_t *buf = avpkt->data;
  52     int buf_size = avpkt->size;
  53     AVSubtitle *sub = data;
  54     const uint8_t *buf_end = buf + buf_size;
  55     uint8_t *bitmap;
  56     int w, h, x, y, i;
  57     int64_t packet_time = 0;
  58     GetBitContext gb;
  59
  60     memset(sub, 0, sizeof(*sub));
  61
  62     // check that at least header fits
  63     if (buf_size < 27 + 7 * 2 + 4 * 3) {
  64         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
  65         return -1;
  66     }
  67
  68     // read start and end time
  69     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
  70         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
  71         return -1;
  72     }
  73     if (avpkt->pts != AV_NOPTS_VALUE)
  74         packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
  75     sub->start_display_time = parse_timecode(buf +  1, packet_time);
  76     sub->end_display_time   = parse_timecode(buf + 14, packet_time);
  77     buf += 27;
  78
  79     // read header
  80     w = bytestream_get_le16(&buf);
  81     h = bytestream_get_le16(&buf);
  82     if (av_image_check_size(w, h, 0, avctx) < 0)
  83         return -1;
  84     x = bytestream_get_le16(&buf);
  85     y = bytestream_get_le16(&buf);
  86     // skip bottom right position, it gives no new information
  87     bytestream_get_le16(&buf);
  88     bytestream_get_le16(&buf);
  89     // The following value is supposed to indicate the start offset
  90     // (relative to the palette) of the data for the second field,
  91     // however there are files in which it has a bogus value and thus
  92     // we just ignore it
  93     bytestream_get_le16(&buf);
  94
  95     // allocate sub and set values
  96     sub->rects =  av_mallocz(sizeof(*sub->rects));
  97     sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
  98     sub->num_rects = 1;
  99     sub->rects[0]->x = x; sub->rects[0]->y = y;
 100     sub->rects[0]->w = w; sub->rects[0]->h = h;
 101     sub->rects[0]->type = SUBTITLE_BITMAP;
 102     sub->rects[0]->pict.linesize[0] = w;
 103     sub->rects[0]->pict.data[0] = av_malloc(w * h);
 104     sub->rects[0]->nb_colors = 4;
 105     sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
 106
 107     // read palette
 108     for (i = 0; i < sub->rects[0]->nb_colors; i++)
 109         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
 110     // make all except background (first entry) non-transparent
 111     for (i = 1; i < sub->rects[0]->nb_colors; i++)
 112         ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
 113
 114     // process RLE-compressed data
 115     init_get_bits(&gb, buf, (buf_end - buf) * 8);
 116     bitmap = sub->rects[0]->pict.data[0];
 117     for (y = 0; y < h; y++) {
 118         // interlaced: do odd lines
 119         if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
 120         for (x = 0; x < w; ) {
 121             int log2 = ff_log2_tab[show_bits(&gb, 8)];
 122             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
 123             int color = get_bits(&gb, 2);
 124             run = FFMIN(run, w - x);
 125             // run length 0 means till end of row
 126             if (!run) run = w - x;
 127             memset(bitmap, color, run);
 128             bitmap += run;
 129             x += run;
 130         }
 131         // interlaced, skip every second line
 132         bitmap += w;
 133         align_get_bits(&gb);
 134     }
 135     *data_size = 1;
 136     return buf_size;
 137 }
 138
 139 AVCodec ff_xsub_decoder = {
 140     .name      = "xsub",
 141     .type      = AVMEDIA_TYPE_SUBTITLE,
 142     .id        = AV_CODEC_ID_XSUB,
 143     .init      = decode_init,
 144     .decode    = decode_frame,
 145     .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
 146 };