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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 FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 {
35 } KgvContext;
36 
37 static void decode_flush(AVCodecContext *avctx)
38 {
39  KgvContext * const c = avctx->priv_data;
40 
41  av_frame_free(&c->prev);
42 }
43 
44 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
45  AVPacket *avpkt)
46 {
47  AVFrame *frame = data;
48  const uint8_t *buf = avpkt->data;
49  const uint8_t *buf_end = buf + avpkt->size;
50  KgvContext * const c = avctx->priv_data;
51  int offsets[8];
52  uint8_t *out, *prev;
53  int outcnt = 0, maxcnt;
54  int w, h, i, res;
55 
56  if (avpkt->size < 2)
57  return AVERROR_INVALIDDATA;
58 
59  w = (buf[0] + 1) * 8;
60  h = (buf[1] + 1) * 8;
61  buf += 2;
62 
63  if ((res = av_image_check_size(w, h, 0, avctx)) < 0)
64  return res;
65 
66  if (w != avctx->width || h != avctx->height) {
67  av_frame_unref(c->prev);
68  avcodec_set_dimensions(avctx, w, h);
69  }
70 
71  maxcnt = w * h;
72 
73  if ((res = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
74  return res;
75  out = frame->data[0];
76  if (c->prev->data[0]) {
77  prev = 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  AV_WN16A(&out[2 * outcnt], code); // rgb555 pixel coded directly
91  outcnt++;
92  } else {
93  int count;
94 
95  if ((code & 0x6000) == 0x6000) {
96  // copy from previous frame
97  int oidx = (code >> 10) & 7;
98  int start;
99 
100  count = (code & 0x3FF) + 3;
101 
102  if (offsets[oidx] < 0) {
103  if (buf_end - 3 < buf)
104  break;
105  offsets[oidx] = AV_RL24(buf);
106  buf += 3;
107  }
108 
109  start = (outcnt + offsets[oidx]) % maxcnt;
110 
111  if (maxcnt - start < count || maxcnt - outcnt < count)
112  break;
113 
114  if (!prev) {
115  av_log(avctx, AV_LOG_ERROR,
116  "Frame reference does not exist\n");
117  break;
118  }
119 
120  memcpy(out + 2 * outcnt, prev + 2 * start, 2 * count);
121  } else {
122  // copy from earlier in this frame
123  int offset = (code & 0x1FFF) + 1;
124 
125  if (!(code & 0x6000)) {
126  count = 2;
127  } else if ((code & 0x6000) == 0x2000) {
128  count = 3;
129  } else {
130  if (buf_end - 1 < buf)
131  break;
132  count = 4 + *buf++;
133  }
134 
135  if (outcnt < offset || maxcnt - outcnt < count)
136  break;
137 
138  av_memcpy_backptr(out + 2 * outcnt, 2 * offset, 2 * count);
139  }
140  outcnt += count;
141  }
142  }
143 
144  if (outcnt - maxcnt)
145  av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
146 
147  av_frame_unref(c->prev);
148  if ((res = av_frame_ref(c->prev, frame)) < 0)
149  return res;
150 
151  *got_frame = 1;
152 
153  return avpkt->size;
154 }
155 
157 {
158  KgvContext * const c = avctx->priv_data;
159 
160  c->prev = av_frame_alloc();
161  if (!c->prev)
162  return AVERROR(ENOMEM);
163 
164  avctx->pix_fmt = AV_PIX_FMT_RGB555;
165  avctx->flags |= CODEC_FLAG_EMU_EDGE;
166 
167  return 0;
168 }
169 
171 {
172  KgvContext * const c = avctx->priv_data;
173  av_frame_free(&c->prev);
174  return 0;
175 }
176 
178  .name = "kgv1",
179  .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),
180  .type = AVMEDIA_TYPE_VIDEO,
181  .id = AV_CODEC_ID_KGV1,
182  .priv_data_size = sizeof(KgvContext),
183  .init = decode_init,
184  .close = decode_end,
185  .decode = decode_frame,
186  .flush = decode_flush,
187  .capabilities = CODEC_CAP_DR1,
188 };