c93.c
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1 /*
2  * Interplay C93 video decoder
3  * Copyright (c) 2007 Anssi Hannula <anssi.hannula@gmail.com>
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 #include "avcodec.h"
23 #include "bytestream.h"
24 
25 typedef struct {
26  AVFrame pictures[2];
29 
30 typedef enum {
38  C93_NOOP = 0x0E,
39  C93_8X8_INTRA = 0x0F,
40 } C93BlockType;
41 
42 #define WIDTH 320
43 #define HEIGHT 192
44 
45 #define C93_HAS_PALETTE 0x01
46 #define C93_FIRST_FRAME 0x02
47 
49 {
50  avctx->pix_fmt = AV_PIX_FMT_PAL8;
51  return 0;
52 }
53 
54 static av_cold int decode_end(AVCodecContext *avctx)
55 {
56  C93DecoderContext * const c93 = avctx->priv_data;
57 
58  if (c93->pictures[0].data[0])
59  avctx->release_buffer(avctx, &c93->pictures[0]);
60  if (c93->pictures[1].data[0])
61  avctx->release_buffer(avctx, &c93->pictures[1]);
62  return 0;
63 }
64 
65 static inline int copy_block(AVCodecContext *avctx, uint8_t *to,
66  uint8_t *from, int offset, int height, int stride)
67 {
68  int i;
69  int width = height;
70  int from_x = offset % WIDTH;
71  int from_y = offset / WIDTH;
72  int overflow = from_x + width - WIDTH;
73 
74  if (!from) {
75  /* silently ignoring predictive blocks in first frame */
76  return 0;
77  }
78 
79  if (from_y + height > HEIGHT) {
80  av_log(avctx, AV_LOG_ERROR, "invalid offset %d during C93 decoding\n",
81  offset);
82  return -1;
83  }
84 
85  if (overflow > 0) {
86  width -= overflow;
87  for (i = 0; i < height; i++) {
88  memcpy(&to[i*stride+width], &from[(from_y+i)*stride], overflow);
89  }
90  }
91 
92  for (i = 0; i < height; i++) {
93  memcpy(&to[i*stride], &from[(from_y+i)*stride+from_x], width);
94  }
95 
96  return 0;
97 }
98 
99 static inline void draw_n_color(uint8_t *out, int stride, int width,
100  int height, int bpp, uint8_t cols[4], uint8_t grps[4], uint32_t col)
101 {
102  int x, y;
103  for (y = 0; y < height; y++) {
104  if (grps)
105  cols[0] = grps[3 * (y >> 1)];
106  for (x = 0; x < width; x++) {
107  if (grps)
108  cols[1]= grps[(x >> 1) + 1];
109  out[x + y*stride] = cols[col & ((1 << bpp) - 1)];
110  col >>= bpp;
111  }
112  }
113 }
114 
115 static int decode_frame(AVCodecContext *avctx, void *data,
116  int *got_frame, AVPacket *avpkt)
117 {
118  const uint8_t *buf = avpkt->data;
119  int buf_size = avpkt->size;
120  C93DecoderContext * const c93 = avctx->priv_data;
121  AVFrame * const newpic = &c93->pictures[c93->currentpic];
122  AVFrame * const oldpic = &c93->pictures[c93->currentpic^1];
123  AVFrame *picture = data;
124  GetByteContext gb;
125  uint8_t *out;
126  int stride, i, x, y, b, bt = 0;
127 
128  c93->currentpic ^= 1;
129 
130  newpic->reference = 1;
133  if (avctx->reget_buffer(avctx, newpic)) {
134  av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
135  return -1;
136  }
137 
138  stride = newpic->linesize[0];
139 
140  bytestream2_init(&gb, buf, buf_size);
141  b = bytestream2_get_byte(&gb);
142  if (b & C93_FIRST_FRAME) {
143  newpic->pict_type = AV_PICTURE_TYPE_I;
144  newpic->key_frame = 1;
145  } else {
146  newpic->pict_type = AV_PICTURE_TYPE_P;
147  newpic->key_frame = 0;
148  }
149 
150  for (y = 0; y < HEIGHT; y += 8) {
151  out = newpic->data[0] + y * stride;
152  for (x = 0; x < WIDTH; x += 8) {
153  uint8_t *copy_from = oldpic->data[0];
154  unsigned int offset, j;
155  uint8_t cols[4], grps[4];
156  C93BlockType block_type;
157 
158  if (!bt)
159  bt = bytestream2_get_byte(&gb);
160 
161  block_type= bt & 0x0F;
162  switch (block_type) {
163  case C93_8X8_FROM_PREV:
164  offset = bytestream2_get_le16(&gb);
165  if (copy_block(avctx, out, copy_from, offset, 8, stride))
166  return -1;
167  break;
168 
169  case C93_4X4_FROM_CURR:
170  copy_from = newpic->data[0];
171  case C93_4X4_FROM_PREV:
172  for (j = 0; j < 8; j += 4) {
173  for (i = 0; i < 8; i += 4) {
174  offset = bytestream2_get_le16(&gb);
175  if (copy_block(avctx, &out[j*stride+i],
176  copy_from, offset, 4, stride))
177  return -1;
178  }
179  }
180  break;
181 
182  case C93_8X8_2COLOR:
183  bytestream2_get_buffer(&gb, cols, 2);
184  for (i = 0; i < 8; i++) {
185  draw_n_color(out + i*stride, stride, 8, 1, 1, cols,
186  NULL, bytestream2_get_byte(&gb));
187  }
188 
189  break;
190 
191  case C93_4X4_2COLOR:
192  case C93_4X4_4COLOR:
193  case C93_4X4_4COLOR_GRP:
194  for (j = 0; j < 8; j += 4) {
195  for (i = 0; i < 8; i += 4) {
196  if (block_type == C93_4X4_2COLOR) {
197  bytestream2_get_buffer(&gb, cols, 2);
198  draw_n_color(out + i + j*stride, stride, 4, 4,
199  1, cols, NULL, bytestream2_get_le16(&gb));
200  } else if (block_type == C93_4X4_4COLOR) {
201  bytestream2_get_buffer(&gb, cols, 4);
202  draw_n_color(out + i + j*stride, stride, 4, 4,
203  2, cols, NULL, bytestream2_get_le32(&gb));
204  } else {
205  bytestream2_get_buffer(&gb, grps, 4);
206  draw_n_color(out + i + j*stride, stride, 4, 4,
207  1, cols, grps, bytestream2_get_le16(&gb));
208  }
209  }
210  }
211  break;
212 
213  case C93_NOOP:
214  break;
215 
216  case C93_8X8_INTRA:
217  for (j = 0; j < 8; j++)
218  bytestream2_get_buffer(&gb, out + j*stride, 8);
219  break;
220 
221  default:
222  av_log(avctx, AV_LOG_ERROR, "unexpected type %x at %dx%d\n",
223  block_type, x, y);
224  return -1;
225  }
226  bt >>= 4;
227  out += 8;
228  }
229  }
230 
231  if (b & C93_HAS_PALETTE) {
232  uint32_t *palette = (uint32_t *) newpic->data[1];
233  for (i = 0; i < 256; i++) {
234  palette[i] = bytestream2_get_be24(&gb);
235  }
236  newpic->palette_has_changed = 1;
237  } else {
238  if (oldpic->data[1])
239  memcpy(newpic->data[1], oldpic->data[1], 256 * 4);
240  }
241 
242  *picture = *newpic;
243  *got_frame = 1;
244 
245  return buf_size;
246 }
247 
249  .name = "c93",
250  .type = AVMEDIA_TYPE_VIDEO,
251  .id = AV_CODEC_ID_C93,
252  .priv_data_size = sizeof(C93DecoderContext),
253  .init = decode_init,
254  .close = decode_end,
255  .decode = decode_frame,
256  .capabilities = CODEC_CAP_DR1,
257  .long_name = NULL_IF_CONFIG_SMALL("Interplay C93"),
258 };