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libavcodec/kgv1dec.c

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00001 /*
00002  * Kega Game Video (KGV1) decoder
00003  * Copyright (c) 2010 Daniel Verkamp
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include "libavutil/intreadwrite.h"
00028 #include "avcodec.h"
00029 
00030 typedef struct {
00031     AVCodecContext *avctx;
00032     AVFrame pic;
00033     uint16_t *prev, *cur;
00034 } KgvContext;
00035 
00036 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
00037 {
00038     const uint8_t *buf = avpkt->data;
00039     const uint8_t *buf_end = buf + avpkt->size;
00040     KgvContext * const c = avctx->priv_data;
00041     int offsets[7];
00042     uint16_t *out, *prev;
00043     int outcnt = 0, maxcnt;
00044     int w, h, i;
00045 
00046     if (avpkt->size < 2)
00047         return -1;
00048 
00049     w = (buf[0] + 1) * 8;
00050     h = (buf[1] + 1) * 8;
00051     buf += 2;
00052 
00053     if (avcodec_check_dimensions(avctx, w, h))
00054         return -1;
00055 
00056     if (w != avctx->width || h != avctx->height)
00057         avcodec_set_dimensions(avctx, w, h);
00058 
00059     maxcnt = w * h;
00060 
00061     out = av_realloc(c->cur, w * h * 2);
00062     if (!out)
00063         return -1;
00064     c->cur = out;
00065 
00066     prev = av_realloc(c->prev, w * h * 2);
00067     if (!prev)
00068         return -1;
00069     c->prev = prev;
00070 
00071     for (i = 0; i < 7; i++)
00072         offsets[i] = -1;
00073 
00074     while (outcnt < maxcnt && buf_end - 2 > buf) {
00075         int code = AV_RL16(buf);
00076         buf += 2;
00077 
00078         if (!(code & 0x8000)) {
00079             out[outcnt++] = code; // rgb555 pixel coded directly
00080         } else {
00081             int count;
00082             uint16_t *inp;
00083 
00084             if ((code & 0x6000) == 0x6000) {
00085                 // copy from previous frame
00086                 int oidx = (code >> 10) & 7;
00087                 int start;
00088 
00089                 count = (code & 0x3FF) + 3;
00090 
00091                 if (offsets[oidx] < 0) {
00092                     if (buf_end - 3 < buf)
00093                         break;
00094                     offsets[oidx] = AV_RL24(buf);
00095                     buf += 3;
00096                 }
00097 
00098                 start = (outcnt + offsets[oidx]) % maxcnt;
00099 
00100                 if (maxcnt - start < count)
00101                     break;
00102 
00103                 inp = prev + start;
00104             } else {
00105                 // copy from earlier in this frame
00106                 int offset = (code & 0x1FFF) + 1;
00107 
00108                 if (!(code & 0x6000)) {
00109                     count = 2;
00110                 } else if ((code & 0x6000) == 0x2000) {
00111                     count = 3;
00112                 } else {
00113                     if (buf_end - 1 < buf)
00114                         break;
00115                     count = 4 + *buf++;
00116                 }
00117 
00118                 if (outcnt < offset)
00119                     break;
00120 
00121                 inp = out + outcnt - offset;
00122             }
00123 
00124             if (maxcnt - outcnt < count)
00125                 break;
00126 
00127             for (i = 0; i < count; i++)
00128                 out[outcnt++] = inp[i];
00129         }
00130     }
00131 
00132     if (outcnt - maxcnt)
00133         av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
00134 
00135     c->pic.data[0]     = (uint8_t *)c->cur;
00136     c->pic.linesize[0] = w * 2;
00137 
00138     *data_size = sizeof(AVFrame);
00139     *(AVFrame*)data = c->pic;
00140 
00141     FFSWAP(uint16_t *, c->cur, c->prev);
00142 
00143     return avpkt->size;
00144 }
00145 
00146 static av_cold int decode_init(AVCodecContext *avctx)
00147 {
00148     KgvContext * const c = avctx->priv_data;
00149 
00150     c->avctx = avctx;
00151     avctx->pix_fmt = PIX_FMT_RGB555;
00152 
00153     return 0;
00154 }
00155 
00156 static av_cold int decode_end(AVCodecContext *avctx)
00157 {
00158     KgvContext * const c = avctx->priv_data;
00159 
00160     av_freep(&c->cur);
00161     av_freep(&c->prev);
00162 
00163     return 0;
00164 }
00165 
00166 AVCodec kgv1_decoder = {
00167     "kgv1",
00168     AVMEDIA_TYPE_VIDEO,
00169     CODEC_ID_KGV1,
00170     sizeof(KgvContext),
00171     decode_init,
00172     NULL,
00173     decode_end,
00174     decode_frame,
00175     .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),
00176 };

Generated on Fri Sep 16 2011 17:17:38 for FFmpeg by  doxygen 1.7.1