libavcodec/kgv1dec.c

   1 /*
   2  * Kega Game Video (KGV1) decoder
   3  * Copyright (c) 2010 Daniel Verkamp
   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 /**
  23  * @file
  24  * Kega Game Video decoder
  25  */
  26
  27 #include "libavutil/common.h"
  28 #include "libavutil/intreadwrite.h"
  29 #include "libavutil/imgutils.h"
  30 #include "avcodec.h"
  31 #include "internal.h"
  32
  33 typedef struct {
  34     AVCodecContext *avctx;
  35     AVFrame prev;
  36 } KgvContext;
  37
  38 static void decode_flush(AVCodecContext *avctx)
  39 {
  40     KgvContext * const c = avctx->priv_data;
  41
  42     av_frame_unref(&c->prev);
  43 }
  44
  45 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
  46                         AVPacket *avpkt)
  47 {
  48     AVFrame *frame = data;
  49     const uint8_t *buf = avpkt->data;
  50     const uint8_t *buf_end = buf + avpkt->size;
  51     KgvContext * const c = avctx->priv_data;
  52     int offsets[8];
  53     uint16_t *out, *prev;
  54     int outcnt = 0, maxcnt;
  55     int w, h, i, res;
  56
  57     if (avpkt->size < 2)
  58         return AVERROR_INVALIDDATA;
  59
  60     w = (buf[0] + 1) * 8;
  61     h = (buf[1] + 1) * 8;
  62     buf += 2;
  63
  64     if ((res = av_image_check_size(w, h, 0, avctx)) < 0)
  65         return res;
  66
  67     if (w != avctx->width || h != avctx->height) {
  68         av_frame_unref(&c->prev);
  69         avcodec_set_dimensions(avctx, w, h);
  70     }
  71
  72     maxcnt = w * h;
  73
  74     if ((res = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
  75         return res;
  76     out  = (uint16_t *) frame->data[0];
  77     if (c->prev.data[0]) {
  78         prev = (uint16_t *) c->prev.data[0];
  79     } else {
  80         prev = NULL;
  81     }
  82
  83     for (i = 0; i < 8; i++)
  84         offsets[i] = -1;
  85
  86     while (outcnt < maxcnt && buf_end - 2 > buf) {
  87         int code = AV_RL16(buf);
  88         buf += 2;
  89
  90         if (!(code & 0x8000)) {
  91             out[outcnt++] = code; // rgb555 pixel coded directly
  92         } else {
  93             int count;
  94             int inp_off;
  95             uint16_t *inp;
  96
  97             if ((code & 0x6000) == 0x6000) {
  98                 // copy from previous frame
  99                 int oidx = (code >> 10) & 7;
 100                 int start;
 101
 102                 count = (code & 0x3FF) + 3;
 103
 104                 if (offsets[oidx] < 0) {
 105                     if (buf_end - 3 < buf)
 106                         break;
 107                     offsets[oidx] = AV_RL24(buf);
 108                     buf += 3;
 109                 }
 110
 111                 start = (outcnt + offsets[oidx]) % maxcnt;
 112
 113                 if (maxcnt - start < count)
 114                     break;
 115
 116                 if (!prev) {
 117                     av_log(avctx, AV_LOG_ERROR,
 118                            "Frame reference does not exist\n");
 119                     break;
 120                 }
 121
 122                 inp = prev;
 123                 inp_off = start;
 124             } else {
 125                 // copy from earlier in this frame
 126                 int offset = (code & 0x1FFF) + 1;
 127
 128                 if (!(code & 0x6000)) {
 129                     count = 2;
 130                 } else if ((code & 0x6000) == 0x2000) {
 131                     count = 3;
 132                 } else {
 133                     if (buf_end - 1 < buf)
 134                         break;
 135                     count = 4 + *buf++;
 136                 }
 137
 138                 if (outcnt < offset)
 139                     break;
 140
 141                 inp = out;
 142                 inp_off = outcnt - offset;
 143             }
 144
 145             if (maxcnt - outcnt < count)
 146                 break;
 147
 148             for (i = inp_off; i < count + inp_off; i++) {
 149                 out[outcnt++] = inp[i];
 150             }
 151         }
 152     }
 153
 154     if (outcnt - maxcnt)
 155         av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
 156
 157     av_frame_unref(&c->prev);
 158     if ((res = av_frame_ref(&c->prev, frame)) < 0)
 159         return res;
 160
 161     *got_frame = 1;
 162
 163     return avpkt->size;
 164 }
 165
 166 static av_cold int decode_init(AVCodecContext *avctx)
 167 {
 168     KgvContext * const c = avctx->priv_data;
 169
 170     c->avctx = avctx;
 171     avctx->pix_fmt = AV_PIX_FMT_RGB555;
 172     avctx->flags  |= CODEC_FLAG_EMU_EDGE;
 173
 174     return 0;
 175 }
 176
 177 static av_cold int decode_end(AVCodecContext *avctx)
 178 {
 179     decode_flush(avctx);
 180     return 0;
 181 }
 182
 183 AVCodec ff_kgv1_decoder = {
 184     .name           = "kgv1",
 185     .type           = AVMEDIA_TYPE_VIDEO,
 186     .id             = AV_CODEC_ID_KGV1,
 187     .priv_data_size = sizeof(KgvContext),
 188     .init           = decode_init,
 189     .close          = decode_end,
 190     .decode         = decode_frame,
 191     .flush          = decode_flush,
 192     .long_name      = NULL_IF_CONFIG_SMALL("Kega Game Video"),
 193     .capabilities   = CODEC_CAP_DR1,
 194 };