libavcodec/xsubdec.c

   1 /*
   2  * XSUB subtitle decoder
   3  * Copyright (c) 2007 Reimar Döffinger
   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 #include "avcodec.h"
  22 #include "get_bits.h"
  23 #include "bytestream.h"
  24
  25 static av_cold int decode_init(AVCodecContext *avctx) {
  26     avctx->pix_fmt = PIX_FMT_PAL8;
  27     return 0;
  28 }
  29
  30 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
  31 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
  32
  33 static uint64_t parse_timecode(const uint8_t *buf) {
  34     int i;
  35     int64_t ms = 0;
  36     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
  37         return AV_NOPTS_VALUE;
  38     for (i = 0; i < sizeof(tc_offsets); i++) {
  39         uint8_t c = buf[tc_offsets[i]] - '0';
  40         if (c > 9) return AV_NOPTS_VALUE;
  41         ms = (ms + c) * tc_muls[i];
  42     }
  43     return ms;
  44 }
  45
  46 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
  47                         AVPacket *avpkt) {
  48     const uint8_t *buf = avpkt->data;
  49     int buf_size = avpkt->size;
  50     AVSubtitle *sub = data;
  51     const uint8_t *buf_end = buf + buf_size;
  52     uint8_t *bitmap;
  53     int w, h, x, y, rlelen, i;
  54     GetBitContext gb;
  55
  56     sub->format = 0;
  57
  58     // check that at least header fits
  59     if (buf_size < 27 + 7 * 2 + 4 * 3) {
  60         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
  61         return -1;
  62     }
  63
  64     // read start and end time
  65     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
  66         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
  67         return -1;
  68     }
  69     sub->start_display_time = parse_timecode(buf +  1);
  70     sub->end_display_time   = parse_timecode(buf + 14);
  71     buf += 27;
  72
  73     // read header
  74     w = bytestream_get_le16(&buf);
  75     h = bytestream_get_le16(&buf);
  76     if (avcodec_check_dimensions(avctx, w, h) < 0)
  77         return -1;
  78     x = bytestream_get_le16(&buf);
  79     y = bytestream_get_le16(&buf);
  80     // skip bottom right position, it gives no new information
  81     bytestream_get_le16(&buf);
  82     bytestream_get_le16(&buf);
  83     rlelen = bytestream_get_le16(&buf);
  84
  85     // allocate sub and set values
  86     if (!sub->rects) {
  87         sub->rects =  av_mallocz(sizeof(*sub->rects));
  88         sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
  89         sub->num_rects = 1;
  90     }
  91     av_freep(&sub->rects[0]->pict.data[0]);
  92     sub->rects[0]->x = x; sub->rects[0]->y = y;
  93     sub->rects[0]->w = w; sub->rects[0]->h = h;
  94     sub->rects[0]->pict.linesize[0] = w;
  95     sub->rects[0]->pict.data[0] = av_malloc(w * h);
  96     sub->rects[0]->nb_colors = 4;
  97     sub->rects[0]->pict.data[1] = av_malloc(sub->rects[0]->nb_colors * 4);
  98
  99     // read palette
 100     for (i = 0; i < sub->rects[0]->nb_colors; i++)
 101         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
 102     // make all except background (first entry) non-transparent
 103     for (i = 1; i < sub->rects[0]->nb_colors; i++)
 104         ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
 105
 106     // process RLE-compressed data
 107     rlelen = FFMIN(rlelen, buf_end - buf);
 108     init_get_bits(&gb, buf, rlelen * 8);
 109     bitmap = sub->rects[0]->pict.data[0];
 110     for (y = 0; y < h; y++) {
 111         // interlaced: do odd lines
 112         if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
 113         for (x = 0; x < w; ) {
 114             int log2 = ff_log2_tab[show_bits(&gb, 8)];
 115             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
 116             int color = get_bits(&gb, 2);
 117             run = FFMIN(run, w - x);
 118             // run length 0 means till end of row
 119             if (!run) run = w - x;
 120             memset(bitmap, color, run);
 121             bitmap += run;
 122             x += run;
 123         }
 124         // interlaced, skip every second line
 125         bitmap += w;
 126         align_get_bits(&gb);
 127     }
 128     *data_size = 1;
 129     return buf_size;
 130 }
 131
 132 AVCodec xsub_decoder = {
 133     "xsub",
 134     CODEC_TYPE_SUBTITLE,
 135     CODEC_ID_XSUB,
 136     0,
 137     decode_init,
 138     NULL,
 139     NULL,
 140     decode_frame,
 141     .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
 142 };