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libavcodec/escape124.c

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00001 /*
00002  * Escape 124 Video Decoder
00003  * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "avcodec.h"
00023 
00024 #define BITSTREAM_READER_LE
00025 #include "get_bits.h"
00026 
00027 typedef union MacroBlock {
00028     uint16_t pixels[4];
00029     uint32_t pixels32[2];
00030 } MacroBlock;
00031 
00032 typedef union SuperBlock {
00033     uint16_t pixels[64];
00034     uint32_t pixels32[32];
00035 } SuperBlock;
00036 
00037 typedef struct CodeBook {
00038     unsigned depth;
00039     unsigned size;
00040     MacroBlock* blocks;
00041 } CodeBook;
00042 
00043 typedef struct Escape124Context {
00044     AVFrame frame;
00045 
00046     unsigned num_superblocks;
00047 
00048     CodeBook codebooks[3];
00049 } Escape124Context;
00050 
00051 static int can_safely_read(GetBitContext* gb, uint64_t bits) {
00052     return get_bits_left(gb) >= bits;
00053 }
00054 
00060 static av_cold int escape124_decode_init(AVCodecContext *avctx)
00061 {
00062     Escape124Context *s = avctx->priv_data;
00063 
00064     avcodec_get_frame_defaults(&s->frame);
00065     avctx->pix_fmt = PIX_FMT_RGB555;
00066 
00067     s->num_superblocks = ((unsigned)avctx->width / 8) *
00068                          ((unsigned)avctx->height / 8);
00069 
00070     return 0;
00071 }
00072 
00073 static av_cold int escape124_decode_close(AVCodecContext *avctx)
00074 {
00075     unsigned i;
00076     Escape124Context *s = avctx->priv_data;
00077 
00078     for (i = 0; i < 3; i++)
00079         av_free(s->codebooks[i].blocks);
00080 
00081     if (s->frame.data[0])
00082         avctx->release_buffer(avctx, &s->frame);
00083 
00084     return 0;
00085 }
00086 
00087 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
00088                                  unsigned size)
00089 {
00090     unsigned i, j;
00091     CodeBook cb = { 0 };
00092 
00093     if (!can_safely_read(gb, size * 34L))
00094         return cb;
00095 
00096     if (size >= INT_MAX / sizeof(MacroBlock))
00097         return cb;
00098     cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
00099     if (!cb.blocks)
00100         return cb;
00101 
00102     cb.depth = depth;
00103     cb.size = size;
00104     for (i = 0; i < size; i++) {
00105         unsigned mask_bits = get_bits(gb, 4);
00106         unsigned color0 = get_bits(gb, 15);
00107         unsigned color1 = get_bits(gb, 15);
00108 
00109         for (j = 0; j < 4; j++) {
00110             if (mask_bits & (1 << j))
00111                 cb.blocks[i].pixels[j] = color1;
00112             else
00113                 cb.blocks[i].pixels[j] = color0;
00114         }
00115     }
00116     return cb;
00117 }
00118 
00119 static unsigned decode_skip_count(GetBitContext* gb)
00120 {
00121     unsigned value;
00122     // This function reads a maximum of 23 bits,
00123     // which is within the padding space
00124     if (!can_safely_read(gb, 1))
00125         return -1;
00126     value = get_bits1(gb);
00127     if (!value)
00128         return value;
00129 
00130     value += get_bits(gb, 3);
00131     if (value != (1 + ((1 << 3) - 1)))
00132         return value;
00133 
00134     value += get_bits(gb, 7);
00135     if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
00136         return value;
00137 
00138     return value + get_bits(gb, 12);
00139 }
00140 
00141 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
00142                                     int* codebook_index, int superblock_index)
00143 {
00144     // This function reads a maximum of 22 bits; the callers
00145     // guard this function appropriately
00146     unsigned block_index, depth;
00147 
00148     if (get_bits1(gb)) {
00149         static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
00150         *codebook_index = transitions[*codebook_index][get_bits1(gb)];
00151     }
00152 
00153     depth = s->codebooks[*codebook_index].depth;
00154 
00155     // depth = 0 means that this shouldn't read any bits;
00156     // in theory, this is the same as get_bits(gb, 0), but
00157     // that doesn't actually work.
00158     block_index = depth ? get_bits(gb, depth) : 0;
00159 
00160     if (*codebook_index == 1) {
00161         block_index += superblock_index << s->codebooks[1].depth;
00162     }
00163 
00164     // This condition can occur with invalid bitstreams and
00165     // *codebook_index == 2
00166     if (block_index >= s->codebooks[*codebook_index].size)
00167         return (MacroBlock) { { 0 } };
00168 
00169     return s->codebooks[*codebook_index].blocks[block_index];
00170 }
00171 
00172 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
00173    // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
00174    uint32_t *dst = sb->pixels32 + index + (index & -4);
00175 
00176    // This technically violates C99 aliasing rules, but it should be safe.
00177    dst[0] = mb.pixels32[0];
00178    dst[4] = mb.pixels32[1];
00179 }
00180 
00181 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
00182                             uint16_t* src, unsigned src_stride)
00183 {
00184     unsigned y;
00185     if (src)
00186         for (y = 0; y < 8; y++)
00187             memcpy(dest + y * dest_stride, src + y * src_stride,
00188                    sizeof(uint16_t) * 8);
00189     else
00190         for (y = 0; y < 8; y++)
00191             memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
00192 }
00193 
00194 static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
00195                                        0x4,   0x8,   0x40,   0x80,
00196                                        0x100, 0x200, 0x1000, 0x2000,
00197                                        0x400, 0x800, 0x4000, 0x8000};
00198 
00199 static int escape124_decode_frame(AVCodecContext *avctx,
00200                                   void *data, int *data_size,
00201                                   AVPacket *avpkt)
00202 {
00203     const uint8_t *buf = avpkt->data;
00204     int buf_size = avpkt->size;
00205     Escape124Context *s = avctx->priv_data;
00206 
00207     GetBitContext gb;
00208     unsigned frame_flags, frame_size;
00209     unsigned i;
00210 
00211     unsigned superblock_index, cb_index = 1,
00212              superblock_col_index = 0,
00213              superblocks_per_row = avctx->width / 8, skip = -1;
00214 
00215     uint16_t* old_frame_data, *new_frame_data;
00216     unsigned old_stride, new_stride;
00217 
00218     AVFrame new_frame;
00219     avcodec_get_frame_defaults(&new_frame);
00220 
00221     init_get_bits(&gb, buf, buf_size * 8);
00222 
00223     // This call also guards the potential depth reads for the
00224     // codebook unpacking.
00225     if (!can_safely_read(&gb, 64))
00226         return -1;
00227 
00228     frame_flags = get_bits_long(&gb, 32);
00229     frame_size  = get_bits_long(&gb, 32);
00230 
00231     // Leave last frame unchanged
00232     // FIXME: Is this necessary?  I haven't seen it in any real samples
00233     if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
00234         av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
00235 
00236         *data_size = sizeof(AVFrame);
00237         *(AVFrame*)data = s->frame;
00238 
00239         return frame_size;
00240     }
00241 
00242     for (i = 0; i < 3; i++) {
00243         if (frame_flags & (1 << (17 + i))) {
00244             unsigned cb_depth, cb_size;
00245             if (i == 2) {
00246                 // This codebook can be cut off at places other than
00247                 // powers of 2, leaving some of the entries undefined.
00248                 cb_size = get_bits_long(&gb, 20);
00249                 cb_depth = av_log2(cb_size - 1) + 1;
00250             } else {
00251                 cb_depth = get_bits(&gb, 4);
00252                 if (i == 0) {
00253                     // This is the most basic codebook: pow(2,depth) entries
00254                     // for a depth-length key
00255                     cb_size = 1 << cb_depth;
00256                 } else {
00257                     // This codebook varies per superblock
00258                     // FIXME: I don't think this handles integer overflow
00259                     // properly
00260                     cb_size = s->num_superblocks << cb_depth;
00261                 }
00262             }
00263             av_free(s->codebooks[i].blocks);
00264             s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
00265             if (!s->codebooks[i].blocks)
00266                 return -1;
00267         }
00268     }
00269 
00270     new_frame.reference = 3;
00271     if (avctx->get_buffer(avctx, &new_frame)) {
00272         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
00273         return -1;
00274     }
00275 
00276     new_frame_data = (uint16_t*)new_frame.data[0];
00277     new_stride = new_frame.linesize[0] / 2;
00278     old_frame_data = (uint16_t*)s->frame.data[0];
00279     old_stride = s->frame.linesize[0] / 2;
00280 
00281     for (superblock_index = 0; superblock_index < s->num_superblocks;
00282          superblock_index++) {
00283         MacroBlock mb;
00284         SuperBlock sb;
00285         unsigned multi_mask = 0;
00286 
00287         if (skip == -1) {
00288             // Note that this call will make us skip the rest of the blocks
00289             // if the frame prematurely ends
00290             skip = decode_skip_count(&gb);
00291         }
00292 
00293         if (skip) {
00294             copy_superblock(new_frame_data, new_stride,
00295                             old_frame_data, old_stride);
00296         } else {
00297             copy_superblock(sb.pixels, 8,
00298                             old_frame_data, old_stride);
00299 
00300             while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
00301                 unsigned mask;
00302                 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
00303                 mask = get_bits(&gb, 16);
00304                 multi_mask |= mask;
00305                 for (i = 0; i < 16; i++) {
00306                     if (mask & mask_matrix[i]) {
00307                         insert_mb_into_sb(&sb, mb, i);
00308                     }
00309                 }
00310             }
00311 
00312             if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
00313                 unsigned inv_mask = get_bits(&gb, 4);
00314                 for (i = 0; i < 4; i++) {
00315                     if (inv_mask & (1 << i)) {
00316                         multi_mask ^= 0xF << i*4;
00317                     } else {
00318                         multi_mask ^= get_bits(&gb, 4) << i*4;
00319                     }
00320                 }
00321 
00322                 for (i = 0; i < 16; i++) {
00323                     if (multi_mask & mask_matrix[i]) {
00324                         if (!can_safely_read(&gb, 1))
00325                             break;
00326                         mb = decode_macroblock(s, &gb, &cb_index,
00327                                                superblock_index);
00328                         insert_mb_into_sb(&sb, mb, i);
00329                     }
00330                 }
00331             } else if (frame_flags & (1 << 16)) {
00332                 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
00333                     mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
00334                     insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
00335                 }
00336             }
00337 
00338             copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
00339         }
00340 
00341         superblock_col_index++;
00342         new_frame_data += 8;
00343         if (old_frame_data)
00344             old_frame_data += 8;
00345         if (superblock_col_index == superblocks_per_row) {
00346             new_frame_data += new_stride * 8 - superblocks_per_row * 8;
00347             if (old_frame_data)
00348                 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
00349             superblock_col_index = 0;
00350         }
00351         skip--;
00352     }
00353 
00354     av_log(NULL, AV_LOG_DEBUG,
00355            "Escape sizes: %i, %i, %i\n",
00356            frame_size, buf_size, get_bits_count(&gb) / 8);
00357 
00358     if (s->frame.data[0])
00359         avctx->release_buffer(avctx, &s->frame);
00360 
00361     *(AVFrame*)data = s->frame = new_frame;
00362     *data_size = sizeof(AVFrame);
00363 
00364     return frame_size;
00365 }
00366 
00367 
00368 AVCodec ff_escape124_decoder = {
00369     .name           = "escape124",
00370     .type           = AVMEDIA_TYPE_VIDEO,
00371     .id             = CODEC_ID_ESCAPE124,
00372     .priv_data_size = sizeof(Escape124Context),
00373     .init           = escape124_decode_init,
00374     .close          = escape124_decode_close,
00375     .decode         = escape124_decode_frame,
00376     .capabilities   = CODEC_CAP_DR1,
00377     .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
00378 };
00379 
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