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/*
* Escape 124 Video Decoder
* Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "avcodec.h"
#define ALT_BITSTREAM_READER_LE
#include "get_bits.h"
typedef union MacroBlock {
uint16_t pixels[4];
uint32_t pixels32[2];
} MacroBlock;
typedef union SuperBlock {
uint16_t pixels[64];
uint32_t pixels32[32];
} SuperBlock;
typedef struct CodeBook {
unsigned depth;
unsigned size;
MacroBlock* blocks;
} CodeBook;
typedef struct Escape124Context {
AVFrame frame;
unsigned num_superblocks;
CodeBook codebooks[3];
} Escape124Context;
static int can_safely_read(GetBitContext* gb, int bits) {
return get_bits_count(gb) + bits <= gb->size_in_bits;
}
/**
* Initialize the decoder
* @param avctx decoder context
* @return 0 success, negative on error
*/
static av_cold int escape124_decode_init(AVCodecContext *avctx)
{
Escape124Context *s = avctx->priv_data;
avctx->pix_fmt = PIX_FMT_RGB555;
s->num_superblocks = ((unsigned)avctx->width / 8) *
((unsigned)avctx->height / 8);
return 0;
}
static av_cold int escape124_decode_close(AVCodecContext *avctx)
{
unsigned i;
Escape124Context *s = avctx->priv_data;
for (i = 0; i < 3; i++)
av_free(s->codebooks[i].blocks);
if (s->frame.data[0])
avctx->release_buffer(avctx, &s->frame);
return 0;
}
static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
unsigned size)
{
unsigned i, j;
CodeBook cb = { 0 };
if (!can_safely_read(gb, size * 34))
return cb;
if (size >= INT_MAX / sizeof(MacroBlock))
return cb;
cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
if (!cb.blocks)
return cb;
cb.depth = depth;
cb.size = size;
for (i = 0; i < size; i++) {
unsigned mask_bits = get_bits(gb, 4);
unsigned color0 = get_bits(gb, 15);
unsigned color1 = get_bits(gb, 15);
for (j = 0; j < 4; j++) {
if (mask_bits & (1 << j))
cb.blocks[i].pixels[j] = color1;
else
cb.blocks[i].pixels[j] = color0;
}
}
return cb;
}
static unsigned decode_skip_count(GetBitContext* gb)
{
unsigned value;
// This function reads a maximum of 23 bits,
// which is within the padding space
if (!can_safely_read(gb, 1))
return -1;
value = get_bits1(gb);
if (!value)
return value;
value += get_bits(gb, 3);
if (value != (1 + ((1 << 3) - 1)))
return value;
value += get_bits(gb, 7);
if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
return value;
return value + get_bits(gb, 12);
}
static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
int* codebook_index, int superblock_index)
{
// This function reads a maximum of 22 bits; the callers
// guard this function appropriately
unsigned block_index, depth;
if (get_bits1(gb)) {
static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
*codebook_index = transitions[*codebook_index][get_bits1(gb)];
}
depth = s->codebooks[*codebook_index].depth;
// depth = 0 means that this shouldn't read any bits;
// in theory, this is the same as get_bits(gb, 0), but
// that doesn't actually work.
block_index = depth ? get_bits(gb, depth) : 0;
if (*codebook_index == 1) {
block_index += superblock_index << s->codebooks[1].depth;
}
// This condition can occur with invalid bitstreams and
// *codebook_index == 2
if (block_index >= s->codebooks[*codebook_index].size)
return (MacroBlock) { { 0 } };
return s->codebooks[*codebook_index].blocks[block_index];
}
static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
// Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
uint32_t *dst = sb->pixels32 + index + (index & -4);
// This technically violates C99 aliasing rules, but it should be safe.
dst[0] = mb.pixels32[0];
dst[4] = mb.pixels32[1];
}
static void copy_superblock(uint16_t* dest, unsigned dest_stride,
uint16_t* src, unsigned src_stride)
{
unsigned y;
if (src)
for (y = 0; y < 8; y++)
memcpy(dest + y * dest_stride, src + y * src_stride,
sizeof(uint16_t) * 8);
else
for (y = 0; y < 8; y++)
memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
}
static const uint16_t mask_matrix[] = {0x1, 0x2, 0x10, 0x20,
0x4, 0x8, 0x40, 0x80,
0x100, 0x200, 0x1000, 0x2000,
0x400, 0x800, 0x4000, 0x8000};
static int escape124_decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
Escape124Context *s = avctx->priv_data;
GetBitContext gb;
unsigned frame_flags, frame_size;
unsigned i;
unsigned superblock_index, cb_index = 1,
superblock_col_index = 0,
superblocks_per_row = avctx->width / 8, skip = -1;
uint16_t* old_frame_data, *new_frame_data;
unsigned old_stride, new_stride;
AVFrame new_frame = { { 0 } };
init_get_bits(&gb, buf, buf_size * 8);
// This call also guards the potential depth reads for the
// codebook unpacking.
if (!can_safely_read(&gb, 64))
return -1;
frame_flags = get_bits_long(&gb, 32);
frame_size = get_bits_long(&gb, 32);
// Leave last frame unchanged
// FIXME: Is this necessary? I haven't seen it in any real samples
if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
*data_size = sizeof(AVFrame);
*(AVFrame*)data = s->frame;
return frame_size;
}
for (i = 0; i < 3; i++) {
if (frame_flags & (1 << (17 + i))) {
unsigned cb_depth, cb_size;
if (i == 2) {
// This codebook can be cut off at places other than
// powers of 2, leaving some of the entries undefined.
cb_size = get_bits_long(&gb, 20);
cb_depth = av_log2(cb_size - 1) + 1;
} else {
cb_depth = get_bits(&gb, 4);
if (i == 0) {
// This is the most basic codebook: pow(2,depth) entries
// for a depth-length key
cb_size = 1 << cb_depth;
} else {
// This codebook varies per superblock
// FIXME: I don't think this handles integer overflow
// properly
cb_size = s->num_superblocks << cb_depth;
}
}
av_free(s->codebooks[i].blocks);
s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
if (!s->codebooks[i].blocks)
return -1;
}
}
new_frame.reference = 3;
if (avctx->get_buffer(avctx, &new_frame)) {
av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
return -1;
}
new_frame_data = (uint16_t*)new_frame.data[0];
new_stride = new_frame.linesize[0] / 2;
old_frame_data = (uint16_t*)s->frame.data[0];
old_stride = s->frame.linesize[0] / 2;
for (superblock_index = 0; superblock_index < s->num_superblocks;
superblock_index++) {
MacroBlock mb;
SuperBlock sb;
unsigned multi_mask = 0;
if (skip == -1) {
// Note that this call will make us skip the rest of the blocks
// if the frame prematurely ends
skip = decode_skip_count(&gb);
}
if (skip) {
copy_superblock(new_frame_data, new_stride,
old_frame_data, old_stride);
} else {
copy_superblock(sb.pixels, 8,
old_frame_data, old_stride);
while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
unsigned mask;
mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
mask = get_bits(&gb, 16);
multi_mask |= mask;
for (i = 0; i < 16; i++) {
if (mask & mask_matrix[i]) {
insert_mb_into_sb(&sb, mb, i);
}
}
}
if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
unsigned inv_mask = get_bits(&gb, 4);
for (i = 0; i < 4; i++) {
if (inv_mask & (1 << i)) {
multi_mask ^= 0xF << i*4;
} else {
multi_mask ^= get_bits(&gb, 4) << i*4;
}
}
for (i = 0; i < 16; i++) {
if (multi_mask & mask_matrix[i]) {
if (!can_safely_read(&gb, 1))
break;
mb = decode_macroblock(s, &gb, &cb_index,
superblock_index);
insert_mb_into_sb(&sb, mb, i);
}
}
} else if (frame_flags & (1 << 16)) {
while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
}
}
copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
}
superblock_col_index++;
new_frame_data += 8;
if (old_frame_data)
old_frame_data += 8;
if (superblock_col_index == superblocks_per_row) {
new_frame_data += new_stride * 8 - superblocks_per_row * 8;
if (old_frame_data)
old_frame_data += old_stride * 8 - superblocks_per_row * 8;
superblock_col_index = 0;
}
skip--;
}
av_log(NULL, AV_LOG_DEBUG,
"Escape sizes: %i, %i, %i\n",
frame_size, buf_size, get_bits_count(&gb) / 8);
if (s->frame.data[0])
avctx->release_buffer(avctx, &s->frame);
*(AVFrame*)data = s->frame = new_frame;
*data_size = sizeof(AVFrame);
return frame_size;
}
AVCodec escape124_decoder = {
"escape124",
AVMEDIA_TYPE_VIDEO,
CODEC_ID_ESCAPE124,
sizeof(Escape124Context),
escape124_decode_init,
NULL,
escape124_decode_close,
escape124_decode_frame,
CODEC_CAP_DR1,
.long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
};
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