Libav 0.7.1
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 #include "libavutil/imgutils.h"
00022 #include "avcodec.h"
00023 #include "get_bits.h"
00024 #include "bytestream.h"
00025 
00026 static av_cold int decode_init(AVCodecContext *avctx) {
00027     avctx->pix_fmt = PIX_FMT_PAL8;
00028     return 0;
00029 }
00030 
00031 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
00032 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 10, 10, 10, 1 };
00033 
00034 static int64_t parse_timecode(const uint8_t *buf, int64_t packet_time) {
00035     int i;
00036     int64_t ms = 0;
00037     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
00038         return AV_NOPTS_VALUE;
00039     for (i = 0; i < sizeof(tc_offsets); i++) {
00040         uint8_t c = buf[tc_offsets[i]] - '0';
00041         if (c > 9) return AV_NOPTS_VALUE;
00042         ms = (ms + c) * tc_muls[i];
00043     }
00044     return ms - packet_time;
00045 }
00046 
00047 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
00048                         AVPacket *avpkt) {
00049     const uint8_t *buf = avpkt->data;
00050     int buf_size = avpkt->size;
00051     AVSubtitle *sub = data;
00052     const uint8_t *buf_end = buf + buf_size;
00053     uint8_t *bitmap;
00054     int w, h, x, y, rlelen, i;
00055     int64_t packet_time = 0;
00056     GetBitContext gb;
00057 
00058     memset(sub, 0, sizeof(*sub));
00059 
00060     // check that at least header fits
00061     if (buf_size < 27 + 7 * 2 + 4 * 3) {
00062         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
00063         return -1;
00064     }
00065 
00066     // read start and end time
00067     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
00068         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
00069         return -1;
00070     }
00071     if (avpkt->pts != AV_NOPTS_VALUE)
00072         packet_time = av_rescale_q(avpkt->pts, AV_TIME_BASE_Q, (AVRational){1, 1000});
00073     sub->start_display_time = parse_timecode(buf +  1, packet_time);
00074     sub->end_display_time   = parse_timecode(buf + 14, packet_time);
00075     buf += 27;
00076 
00077     // read header
00078     w = bytestream_get_le16(&buf);
00079     h = bytestream_get_le16(&buf);
00080     if (av_image_check_size(w, h, 0, avctx) < 0)
00081         return -1;
00082     x = bytestream_get_le16(&buf);
00083     y = bytestream_get_le16(&buf);
00084     // skip bottom right position, it gives no new information
00085     bytestream_get_le16(&buf);
00086     bytestream_get_le16(&buf);
00087     rlelen = bytestream_get_le16(&buf);
00088 
00089     // allocate sub and set values
00090     sub->rects =  av_mallocz(sizeof(*sub->rects));
00091     sub->rects[0] = av_mallocz(sizeof(*sub->rects[0]));
00092     sub->num_rects = 1;
00093     sub->rects[0]->x = x; sub->rects[0]->y = y;
00094     sub->rects[0]->w = w; sub->rects[0]->h = h;
00095     sub->rects[0]->type = SUBTITLE_BITMAP;
00096     sub->rects[0]->pict.linesize[0] = w;
00097     sub->rects[0]->pict.data[0] = av_malloc(w * h);
00098     sub->rects[0]->nb_colors = 4;
00099     sub->rects[0]->pict.data[1] = av_mallocz(AVPALETTE_SIZE);
00100 
00101     // read palette
00102     for (i = 0; i < sub->rects[0]->nb_colors; i++)
00103         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
00104     // make all except background (first entry) non-transparent
00105     for (i = 1; i < sub->rects[0]->nb_colors; i++)
00106         ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
00107 
00108     // process RLE-compressed data
00109     rlelen = FFMIN(rlelen, buf_end - buf);
00110     init_get_bits(&gb, buf, rlelen * 8);
00111     bitmap = sub->rects[0]->pict.data[0];
00112     for (y = 0; y < h; y++) {
00113         // interlaced: do odd lines
00114         if (y == (h + 1) / 2) bitmap = sub->rects[0]->pict.data[0] + w;
00115         for (x = 0; x < w; ) {
00116             int log2 = ff_log2_tab[show_bits(&gb, 8)];
00117             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
00118             int color = get_bits(&gb, 2);
00119             run = FFMIN(run, w - x);
00120             // run length 0 means till end of row
00121             if (!run) run = w - x;
00122             memset(bitmap, color, run);
00123             bitmap += run;
00124             x += run;
00125         }
00126         // interlaced, skip every second line
00127         bitmap += w;
00128         align_get_bits(&gb);
00129     }
00130     *data_size = 1;
00131     return buf_size;
00132 }
00133 
00134 AVCodec ff_xsub_decoder = {
00135     "xsub",
00136     AVMEDIA_TYPE_SUBTITLE,
00137     CODEC_ID_XSUB,
00138     0,
00139     decode_init,
00140     NULL,
00141     NULL,
00142     decode_frame,
00143     .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
00144 };