• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • Examples
  • File List
  • Globals

libavcodec/xsubdec.c

Go to the documentation of this file.
00001 /*
00002  * XSUB subtitle decoder
00003  * Copyright (c) 2007 Reimar Döffinger
00004  *
00005  * This file is part of Libav.
00006  *
00007  * Libav is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * Libav is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with Libav; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "libavutil/mathematics.h"
00023 #include "libavutil/imgutils.h"
00024 #include "avcodec.h"
00025 #include "get_bits.h"
00026 #include "bytestream.h"
00027 
00028 static av_cold int decode_init(AVCodecContext *avctx) {
00029     avctx->pix_fmt = PIX_FMT_PAL8;
00030     return 0;
00031 }
00032 
00033 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
00034 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
00035 
00036 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
00037     int i;
00038     int64_t ms = 0;
00039     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
00040         return AV_NOPTS_VALUE;
00041     for (i = 0; i < sizeof(tc_offsets); i++) {
00042         uint8_t c = buf[tc_offsets[i]] - '0';
00043         if (c > 9) return AV_NOPTS_VALUE;
00044         ms = (ms + c) * tc_muls[i];
00045     }
00046     return ms - packet_time;
00047 }
00048 
00049 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
00050                         AVPacket *avpkt) {
00051     const uint8_t *buf = avpkt->data;
00052     int buf_size = avpkt->size;
00053     AVSubtitle *sub = data;
00054     const uint8_t *buf_end = buf + buf_size;
00055     uint8_t *bitmap;
00056     int w, h, x, y, rlelen, i;
00057     int64_t packet_time = 0;
00058     GetBitContext gb;
00059 
00060     memset(sub, 0, sizeof(*sub));
00061 
00062     // check that at least header fits
00063     if (buf_size < 27 + 7 * 2 + 4 * 3) {
00064         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
00065         return -1;
00066     }
00067 
00068     // read start and end time
00069     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
00070         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
00071         return -1;
00072     }
00073     if (avpkt->pts != AV_NOPTS_VALUE)
00074         packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
00075     sub->start_display_time = parse_timecode(buf +  1, packet_time);
00076     sub->end_display_time   = parse_timecode(buf + 14, packet_time);
00077     buf += 27;
00078 
00079     // read header
00080     w = bytestream_get_le16(&buf);
00081     h = bytestream_get_le16(&buf);
00082     if (av_image_check_size(w, h, 0, avctx) < 0)
00083         return -1;
00084     x = bytestream_get_le16(&buf);
00085     y = bytestream_get_le16(&buf);
00086     // skip bottom right position, it gives no new information
00087     bytestream_get_le16(&buf);
00088     bytestream_get_le16(&buf);
00089     rlelen = bytestream_get_le16(&buf);
00090 
00091     // allocate sub and set values
00092     sub->rects =  av_mallocz(sizeof(*sub->rects));
00093     sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
00094     sub->num_rects = 1;
00095     sub->rects[0]->x = x; sub->rects[0]->y = y;
00096     sub->rects[0]->w = w; sub->rects[0]->h = h;
00097     sub->rects[0]->type = SUBTITLE_BITMAP;
00098     sub->rects[0]->pict.linesize[0] = w;
00099     sub->rects[0]->pict.data[0] = av_malloc(w * h);
00100     sub->rects[0]->nb_colors = 4;
00101     sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
00102 
00103     // read palette
00104     for (i = 0; i < sub->rects[0]->nb_colors; i++)
00105         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
00106     // make all except background (first entry) non-transparent
00107     for (i = 1; i < sub->rects[0]->nb_colors; i++)
00108         ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
00109 
00110     // process RLE-compressed data
00111     rlelen = FFMIN(rlelen, buf_end - buf);
00112     init_get_bits(&gb, buf, rlelen * 8);
00113     bitmap = sub->rects[0]->pict.data[0];
00114     for (y = 0; y < h; y++) {
00115         // interlaced: do odd lines
00116         if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
00117         for (x = 0; x < w; ) {
00118             int log2 = ff_log2_tab[show_bits(&gb, 8)];
00119             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
00120             int color = get_bits(&gb, 2);
00121             run = FFMIN(run, w - x);
00122             // run length 0 means till end of row
00123             if (!run) run = w - x;
00124             memset(bitmap, color, run);
00125             bitmap += run;
00126             x += run;
00127         }
00128         // interlaced, skip every second line
00129         bitmap += w;
00130         align_get_bits(&gb);
00131     }
00132     *data_size = 1;
00133     return buf_size;
00134 }
00135 
00136 AVCodec ff_xsub_decoder = {
00137     .name      = "xsub",
00138     .type      = AVMEDIA_TYPE_SUBTITLE,
00139     .id        = CODEC_ID_XSUB,
00140     .init      = decode_init,
00141     .decode    = decode_frame,
00142     .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
00143 };
Generated on Sun Apr 22 2012 21:54:06 for Libav by doxygen 1.7.1