--- /dev/null
+/*
+ * 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 "bitstream.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]);
+
+ 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;
+
+ if (!can_safely_read(gb, size * 34))
+ return NULL;
+
+ if (size >= (INT_MAX - sizeof(CodeBook)) / sizeof(MacroBlock))
+ return NULL;
+ cb = av_malloc(size * sizeof(MacroBlock) + sizeof(CodeBook));
+ if (!cb)
+ return NULL;
+
+ 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};
+
+/**
+ * Decode a single frame
+ * @param avctx decoder context
+ * @param data decoded frame
+ * @param data_size size of the decoded frame
+ * @param buf input buffer
+ * @param buf_size input buffer size
+ * @return 0 success, -1 on error
+ */
+static int escape124_decode_frame(AVCodecContext *avctx,
+ void *data, int *data_size,
+ const uint8_t *buf, int buf_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]);
+ s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
+ if (!s->codebooks[i])
+ 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",
+ CODEC_TYPE_VIDEO,
+ CODEC_ID_ESCAPE124,
+ sizeof(Escape124Context),
+ escape124_decode_init,
+ NULL,
+ escape124_decode_close,
+ escape124_decode_frame,
+ CODEC_CAP_DR1,
+};
+