kgv1dec.c
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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 
27 #include "libavutil/intreadwrite.h"
28 #include "libavutil/imgutils.h"
29 #include "avcodec.h"
30 
31 typedef struct {
33  AVFrame prev, cur;
34 } KgvContext;
35 
36 static void decode_flush(AVCodecContext *avctx)
37 {
38  KgvContext * const c = avctx->priv_data;
39 
40  if (c->prev.data[0])
41  avctx->release_buffer(avctx, &c->prev);
42 }
43 
44 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
45 {
46  const uint8_t *buf = avpkt->data;
47  const uint8_t *buf_end = buf + avpkt->size;
48  KgvContext * const c = avctx->priv_data;
49  int offsets[8];
50  uint16_t *out, *prev;
51  int outcnt = 0, maxcnt;
52  int w, h, i, res;
53 
54  if (avpkt->size < 2)
55  return -1;
56 
57  w = (buf[0] + 1) * 8;
58  h = (buf[1] + 1) * 8;
59  buf += 2;
60 
61  if (av_image_check_size(w, h, 0, avctx))
62  return -1;
63 
64  if (w != avctx->width || h != avctx->height) {
65  if (c->prev.data[0])
66  avctx->release_buffer(avctx, &c->prev);
67  avcodec_set_dimensions(avctx, w, h);
68  }
69 
70  maxcnt = w * h;
71 
72  c->cur.reference = 3;
73  if ((res = avctx->get_buffer(avctx, &c->cur)) < 0)
74  return res;
75  out = (uint16_t *) c->cur.data[0];
76  if (c->prev.data[0]) {
77  prev = (uint16_t *) c->prev.data[0];
78  } else {
79  prev = NULL;
80  }
81 
82  for (i = 0; i < 8; i++)
83  offsets[i] = -1;
84 
85  while (outcnt < maxcnt && buf_end - 2 > buf) {
86  int code = AV_RL16(buf);
87  buf += 2;
88 
89  if (!(code & 0x8000)) {
90  out[outcnt++] = code; // rgb555 pixel coded directly
91  } else {
92  int count;
93  int inp_off;
94  uint16_t *inp;
95 
96  if ((code & 0x6000) == 0x6000) {
97  // copy from previous frame
98  int oidx = (code >> 10) & 7;
99  int start;
100 
101  count = (code & 0x3FF) + 3;
102 
103  if (offsets[oidx] < 0) {
104  if (buf_end - 3 < buf)
105  break;
106  offsets[oidx] = AV_RL24(buf);
107  buf += 3;
108  }
109 
110  start = (outcnt + offsets[oidx]) % maxcnt;
111 
112  if (maxcnt - start < count)
113  break;
114 
115  if (!prev) {
116  av_log(avctx, AV_LOG_ERROR,
117  "Frame reference does not exist\n");
118  break;
119  }
120 
121  inp = prev;
122  inp_off = start;
123  } else {
124  // copy from earlier in this frame
125  int offset = (code & 0x1FFF) + 1;
126 
127  if (!(code & 0x6000)) {
128  count = 2;
129  } else if ((code & 0x6000) == 0x2000) {
130  count = 3;
131  } else {
132  if (buf_end - 1 < buf)
133  break;
134  count = 4 + *buf++;
135  }
136 
137  if (outcnt < offset)
138  break;
139 
140  inp = out;
141  inp_off = outcnt - offset;
142  }
143 
144  if (maxcnt - outcnt < count)
145  break;
146 
147  for (i = inp_off; i < count + inp_off; i++) {
148  out[outcnt++] = inp[i];
149  }
150  }
151  }
152 
153  if (outcnt - maxcnt)
154  av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
155 
156  *data_size = sizeof(AVFrame);
157  *(AVFrame*)data = c->cur;
158 
159  if (c->prev.data[0])
160  avctx->release_buffer(avctx, &c->prev);
161  FFSWAP(AVFrame, c->cur, c->prev);
162 
163  return avpkt->size;
164 }
165 
167 {
168  KgvContext * const c = avctx->priv_data;
169 
170  c->avctx = avctx;
171  avctx->pix_fmt = PIX_FMT_RGB555;
172  avctx->flags |= CODEC_FLAG_EMU_EDGE;
173 
174  return 0;
175 }
176 
178 {
179  decode_flush(avctx);
180  return 0;
181 }
182 
184  .name = "kgv1",
185  .type = AVMEDIA_TYPE_VIDEO,
186  .id = 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 };