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
22 #define BITSTREAM_READER_LE
24 #include "codec_internal.h"
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 avctx->pix_fmt = AV_PIX_FMT_RGB555;
63 s->num_superblocks = ((unsigned)avctx->width / 8) *
64 ((unsigned)avctx->height / 8);
66 s->frame = av_frame_alloc();
68 return AVERROR(ENOMEM);
73 static av_cold int escape124_decode_close(AVCodecContext *avctx)
76 Escape124Context *s = avctx->priv_data;
78 for (i = 0; i < 3; i++)
79 av_freep(&s->codebooks[i].blocks);
81 av_frame_free(&s->frame);
86 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
92 cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
98 for (i = 0; i < size; i++) {
99 unsigned mask_bits = get_bits(gb, 4);
101 color[0] = get_bits(gb, 15);
102 color[1] = get_bits(gb, 15);
104 for (j = 0; j < 4; j++)
105 cb.blocks[i].pixels[j] = color[(mask_bits>>j) & 1];
110 static unsigned decode_skip_count(GetBitContext* gb)
113 // This function reads a maximum of 23 bits,
114 // which is within the padding space
115 if (get_bits_left(gb) < 1)
117 value = get_bits1(gb);
121 value += get_bits(gb, 3);
122 if (value != (1 + ((1 << 3) - 1)))
125 value += get_bits(gb, 7);
126 if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
129 return value + get_bits(gb, 12);
132 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
133 int* codebook_index, int superblock_index)
135 // This function reads a maximum of 22 bits; the callers
136 // guard this function appropriately
137 unsigned block_index, depth;
138 int value = get_bits1(gb);
140 static const int8_t transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
141 value = get_bits1(gb);
142 *codebook_index = transitions[*codebook_index][value];
145 depth = s->codebooks[*codebook_index].depth;
147 // depth = 0 means that this shouldn't read any bits;
148 // in theory, this is the same as get_bits(gb, 0), but
149 // that doesn't actually work.
150 block_index = get_bitsz(gb, depth);
152 if (*codebook_index == 1) {
153 block_index += superblock_index << s->codebooks[1].depth;
156 // This condition can occur with invalid bitstreams and
157 // *codebook_index == 2
158 if (block_index >= s->codebooks[*codebook_index].size || !s->codebooks[*codebook_index].blocks)
159 return (MacroBlock) { { 0 } };
161 return s->codebooks[*codebook_index].blocks[block_index];
164 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
165 // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
166 uint32_t *dst = sb->pixels32 + index + (index & -4);
168 // This technically violates C99 aliasing rules, but it should be safe.
169 dst[0] = mb.pixels32[0];
170 dst[4] = mb.pixels32[1];
173 static void copy_superblock(uint16_t* dest, ptrdiff_t dest_stride,
174 uint16_t* src, ptrdiff_t src_stride)
178 for (y = 0; y < 8; y++)
179 memcpy(dest + y * dest_stride, src + y * src_stride,
180 sizeof(uint16_t) * 8);
182 for (y = 0; y < 8; y++)
183 memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
186 static const uint16_t mask_matrix[] = {0x1, 0x2, 0x10, 0x20,
187 0x4, 0x8, 0x40, 0x80,
188 0x100, 0x200, 0x1000, 0x2000,
189 0x400, 0x800, 0x4000, 0x8000};
191 static int escape124_decode_frame(AVCodecContext *avctx, AVFrame *frame,
192 int *got_frame, AVPacket *avpkt)
194 int buf_size = avpkt->size;
195 Escape124Context *s = avctx->priv_data;
198 unsigned frame_flags, frame_size;
201 unsigned superblock_index, cb_index = 1,
202 superblock_col_index = 0,
203 superblocks_per_row = avctx->width / 8, skip = -1;
205 uint16_t* old_frame_data, *new_frame_data;
206 ptrdiff_t old_stride, new_stride;
210 if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
213 // This call also guards the potential depth reads for the
214 // codebook unpacking.
215 // Check if the amount we will read minimally is available on input.
216 // The 64 represent the immediately next 2 frame_* elements read, the 23/4320
217 // represent a lower bound of the space needed for skipped superblocks. Non
218 // skipped SBs need more space.
219 if (get_bits_left(&gb) < 64 + s->num_superblocks * 23LL / 4320)
220 return AVERROR_INVALIDDATA;
222 frame_flags = get_bits_long(&gb, 32);
223 frame_size = get_bits_long(&gb, 32);
225 // Leave last frame unchanged
226 // FIXME: Is this necessary? I haven't seen it in any real samples
227 if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
228 if (!s->frame->data[0])
229 return AVERROR_INVALIDDATA;
231 av_log(avctx, AV_LOG_DEBUG, "Skipping frame\n");
234 if ((ret = av_frame_ref(frame, s->frame)) < 0)
240 for (i = 0; i < 3; i++) {
241 if (frame_flags & (1 << (17 + i))) {
242 unsigned cb_depth, cb_size;
244 // This codebook can be cut off at places other than
245 // powers of 2, leaving some of the entries undefined.
246 cb_size = get_bits(&gb, 20);
248 av_log(avctx, AV_LOG_ERROR, "Invalid codebook size 0.\n");
249 return AVERROR_INVALIDDATA;
251 cb_depth = av_log2(cb_size - 1) + 1;
253 cb_depth = get_bits(&gb, 4);
255 // This is the most basic codebook: pow(2,depth) entries
256 // for a depth-length key
257 cb_size = 1 << cb_depth;
259 // This codebook varies per superblock
260 // FIXME: I don't think this handles integer overflow
262 cb_size = s->num_superblocks << cb_depth;
265 if (s->num_superblocks >= INT_MAX >> cb_depth) {
266 av_log(avctx, AV_LOG_ERROR, "Depth or num_superblocks are too large\n");
267 return AVERROR_INVALIDDATA;
270 av_freep(&s->codebooks[i].blocks);
271 if (cb_size >= INT_MAX / 34 || get_bits_left(&gb) < (int)cb_size * 34)
272 return AVERROR_INVALIDDATA;
274 if (cb_size >= INT_MAX / sizeof(MacroBlock))
275 return AVERROR_INVALIDDATA;
276 s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
277 if (!s->codebooks[i].blocks)
278 return AVERROR(ENOMEM);
282 if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
285 new_frame_data = (uint16_t*)frame->data[0];
286 new_stride = frame->linesize[0] / 2;
287 old_frame_data = (uint16_t*)s->frame->data[0];
288 old_stride = s->frame->linesize[0] / 2;
290 for (superblock_index = 0; superblock_index < s->num_superblocks;
291 superblock_index++) {
294 unsigned multi_mask = 0;
297 // Note that this call will make us skip the rest of the blocks
298 // if the frame prematurely ends
299 skip = decode_skip_count(&gb);
303 copy_superblock(new_frame_data, new_stride,
304 old_frame_data, old_stride);
306 copy_superblock(sb.pixels, 8,
307 old_frame_data, old_stride);
309 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
311 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
312 mask = get_bits(&gb, 16);
314 for (i = 0; i < 16; i++) {
315 if (mask & mask_matrix[i]) {
316 insert_mb_into_sb(&sb, mb, i);
321 if (!get_bits1(&gb)) {
322 unsigned inv_mask = get_bits(&gb, 4);
323 for (i = 0; i < 4; i++) {
324 if (inv_mask & (1 << i)) {
325 multi_mask ^= 0xF << i*4;
327 multi_mask ^= get_bits(&gb, 4) << i*4;
331 for (i = 0; i < 16; i++) {
332 if (multi_mask & mask_matrix[i]) {
333 mb = decode_macroblock(s, &gb, &cb_index,
335 insert_mb_into_sb(&sb, mb, i);
338 } else if (frame_flags & (1 << 16)) {
339 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
340 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
341 insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
345 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
348 superblock_col_index++;
352 if (superblock_col_index == superblocks_per_row) {
353 new_frame_data += new_stride * 8 - superblocks_per_row * 8;
355 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
356 superblock_col_index = 0;
361 av_log(avctx, AV_LOG_DEBUG,
362 "Escape sizes: %i, %i, %i\n",
363 frame_size, buf_size, get_bits_count(&gb) / 8);
365 if ((ret = av_frame_replace(s->frame, frame)) < 0)
374 const FFCodec ff_escape124_decoder = {
375 .p.name = "escape124",
376 CODEC_LONG_NAME("Escape 124"),
377 .p.type = AVMEDIA_TYPE_VIDEO,
378 .p.id = AV_CODEC_ID_ESCAPE124,
379 .priv_data_size = sizeof(Escape124Context),
380 .init = escape124_decode_init,
381 .close = escape124_decode_close,
382 FF_CODEC_DECODE_CB(escape124_decode_frame),
383 .p.capabilities = AV_CODEC_CAP_DR1,