2 * Escape 124 Video Decoder
3 * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
5 * This file is part of FFmpeg.
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.
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.
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
25 #define BITSTREAM_READER_LE
28 typedef union MacroBlock {
33 typedef union SuperBlock {
35 uint32_t pixels32[32];
38 typedef struct CodeBook {
44 typedef struct Escape124Context {
47 unsigned num_superblocks;
49 CodeBook codebooks[3];
53 * Initialize the decoder
54 * @param avctx decoder context
55 * @return 0 success, negative on error
57 static av_cold int escape124_decode_init(AVCodecContext *avctx)
59 Escape124Context *s = avctx->priv_data;
61 avcodec_get_frame_defaults(&s->frame);
62 avctx->pix_fmt = AV_PIX_FMT_RGB555;
64 s->num_superblocks = ((unsigned)avctx->width / 8) *
65 ((unsigned)avctx->height / 8);
70 static av_cold int escape124_decode_close(AVCodecContext *avctx)
73 Escape124Context *s = avctx->priv_data;
75 for (i = 0; i < 3; i++)
76 av_free(s->codebooks[i].blocks);
78 av_frame_unref(&s->frame);
83 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
89 if (size >= INT_MAX / 34 || get_bits_left(gb) < size * 34)
92 if (size >= INT_MAX / sizeof(MacroBlock))
94 cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
100 for (i = 0; i < size; i++) {
101 unsigned mask_bits = get_bits(gb, 4);
102 unsigned color0 = get_bits(gb, 15);
103 unsigned color1 = get_bits(gb, 15);
105 for (j = 0; j < 4; j++) {
106 if (mask_bits & (1 << j))
107 cb.blocks[i].pixels[j] = color1;
109 cb.blocks[i].pixels[j] = color0;
115 static unsigned decode_skip_count(GetBitContext* gb)
118 // This function reads a maximum of 23 bits,
119 // which is within the padding space
120 if (get_bits_left(gb) < 1)
122 value = get_bits1(gb);
126 value += get_bits(gb, 3);
127 if (value != (1 + ((1 << 3) - 1)))
130 value += get_bits(gb, 7);
131 if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
134 return value + get_bits(gb, 12);
137 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
138 int* codebook_index, int superblock_index)
140 // This function reads a maximum of 22 bits; the callers
141 // guard this function appropriately
142 unsigned block_index, depth;
145 static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
146 *codebook_index = transitions[*codebook_index][get_bits1(gb)];
149 depth = s->codebooks[*codebook_index].depth;
151 // depth = 0 means that this shouldn't read any bits;
152 // in theory, this is the same as get_bits(gb, 0), but
153 // that doesn't actually work.
154 block_index = depth ? get_bits(gb, depth) : 0;
156 if (*codebook_index == 1) {
157 block_index += superblock_index << s->codebooks[1].depth;
160 // This condition can occur with invalid bitstreams and
161 // *codebook_index == 2
162 if (block_index >= s->codebooks[*codebook_index].size)
163 return (MacroBlock) { { 0 } };
165 return s->codebooks[*codebook_index].blocks[block_index];
168 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
169 // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
170 uint32_t *dst = sb->pixels32 + index + (index & -4);
172 // This technically violates C99 aliasing rules, but it should be safe.
173 dst[0] = mb.pixels32[0];
174 dst[4] = mb.pixels32[1];
177 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
178 uint16_t* src, unsigned src_stride)
182 for (y = 0; y < 8; y++)
183 memcpy(dest + y * dest_stride, src + y * src_stride,
184 sizeof(uint16_t) * 8);
186 for (y = 0; y < 8; y++)
187 memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
190 static const uint16_t mask_matrix[] = {0x1, 0x2, 0x10, 0x20,
191 0x4, 0x8, 0x40, 0x80,
192 0x100, 0x200, 0x1000, 0x2000,
193 0x400, 0x800, 0x4000, 0x8000};
195 static int escape124_decode_frame(AVCodecContext *avctx,
196 void *data, int *got_frame,
199 int buf_size = avpkt->size;
200 Escape124Context *s = avctx->priv_data;
201 AVFrame *frame = data;
204 unsigned frame_flags, frame_size;
207 unsigned superblock_index, cb_index = 1,
208 superblock_col_index = 0,
209 superblocks_per_row = avctx->width / 8, skip = -1;
211 uint16_t* old_frame_data, *new_frame_data;
212 unsigned old_stride, new_stride;
216 if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
219 // This call also guards the potential depth reads for the
220 // codebook unpacking.
221 if (get_bits_left(&gb) < 64)
224 frame_flags = get_bits_long(&gb, 32);
225 frame_size = get_bits_long(&gb, 32);
227 // Leave last frame unchanged
228 // FIXME: Is this necessary? I haven't seen it in any real samples
229 if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
230 if (!s->frame.data[0])
231 return AVERROR_INVALIDDATA;
233 av_log(avctx, AV_LOG_DEBUG, "Skipping frame\n");
236 if ((ret = av_frame_ref(frame, &s->frame)) < 0)
242 for (i = 0; i < 3; i++) {
243 if (frame_flags & (1 << (17 + i))) {
244 unsigned cb_depth, cb_size;
246 // This codebook can be cut off at places other than
247 // powers of 2, leaving some of the entries undefined.
248 cb_size = get_bits_long(&gb, 20);
249 cb_depth = av_log2(cb_size - 1) + 1;
251 cb_depth = get_bits(&gb, 4);
253 // This is the most basic codebook: pow(2,depth) entries
254 // for a depth-length key
255 cb_size = 1 << cb_depth;
257 // This codebook varies per superblock
258 // FIXME: I don't think this handles integer overflow
260 cb_size = s->num_superblocks << cb_depth;
263 av_free(s->codebooks[i].blocks);
264 s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
265 if (!s->codebooks[i].blocks)
270 if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
273 new_frame_data = (uint16_t*)frame->data[0];
274 new_stride = frame->linesize[0] / 2;
275 old_frame_data = (uint16_t*)s->frame.data[0];
276 old_stride = s->frame.linesize[0] / 2;
278 for (superblock_index = 0; superblock_index < s->num_superblocks;
279 superblock_index++) {
282 unsigned multi_mask = 0;
285 // Note that this call will make us skip the rest of the blocks
286 // if the frame prematurely ends
287 skip = decode_skip_count(&gb);
291 copy_superblock(new_frame_data, new_stride,
292 old_frame_data, old_stride);
294 copy_superblock(sb.pixels, 8,
295 old_frame_data, old_stride);
297 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
299 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
300 mask = get_bits(&gb, 16);
302 for (i = 0; i < 16; i++) {
303 if (mask & mask_matrix[i]) {
304 insert_mb_into_sb(&sb, mb, i);
309 if (!get_bits1(&gb)) {
310 unsigned inv_mask = get_bits(&gb, 4);
311 for (i = 0; i < 4; i++) {
312 if (inv_mask & (1 << i)) {
313 multi_mask ^= 0xF << i*4;
315 multi_mask ^= get_bits(&gb, 4) << i*4;
319 for (i = 0; i < 16; i++) {
320 if (multi_mask & mask_matrix[i]) {
321 mb = decode_macroblock(s, &gb, &cb_index,
323 insert_mb_into_sb(&sb, mb, i);
326 } else if (frame_flags & (1 << 16)) {
327 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
328 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
329 insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
333 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
336 superblock_col_index++;
340 if (superblock_col_index == superblocks_per_row) {
341 new_frame_data += new_stride * 8 - superblocks_per_row * 8;
343 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
344 superblock_col_index = 0;
349 av_log(avctx, AV_LOG_DEBUG,
350 "Escape sizes: %i, %i, %i\n",
351 frame_size, buf_size, get_bits_count(&gb) / 8);
353 av_frame_unref(&s->frame);
354 if ((ret = av_frame_ref(&s->frame, frame)) < 0)
363 AVCodec ff_escape124_decoder = {
365 .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
366 .type = AVMEDIA_TYPE_VIDEO,
367 .id = AV_CODEC_ID_ESCAPE124,
368 .priv_data_size = sizeof(Escape124Context),
369 .init = escape124_decode_init,
370 .close = escape124_decode_close,
371 .decode = escape124_decode_frame,
372 .capabilities = CODEC_CAP_DR1,