yading@10: /*
yading@10:  * Escape 124 Video Decoder
yading@10:  * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: #include "avcodec.h"
yading@10: #include "internal.h"
yading@10: 
yading@10: #define BITSTREAM_READER_LE
yading@10: #include "get_bits.h"
yading@10: 
yading@10: typedef union MacroBlock {
yading@10:     uint16_t pixels[4];
yading@10:     uint32_t pixels32[2];
yading@10: } MacroBlock;
yading@10: 
yading@10: typedef union SuperBlock {
yading@10:     uint16_t pixels[64];
yading@10:     uint32_t pixels32[32];
yading@10: } SuperBlock;
yading@10: 
yading@10: typedef struct CodeBook {
yading@10:     unsigned depth;
yading@10:     unsigned size;
yading@10:     MacroBlock* blocks;
yading@10: } CodeBook;
yading@10: 
yading@10: typedef struct Escape124Context {
yading@10:     AVFrame frame;
yading@10: 
yading@10:     unsigned num_superblocks;
yading@10: 
yading@10:     CodeBook codebooks[3];
yading@10: } Escape124Context;
yading@10: 
yading@10: static int can_safely_read(GetBitContext* gb, uint64_t bits) {
yading@10:     return get_bits_left(gb) >= bits;
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Initialize the decoder
yading@10:  * @param avctx decoder context
yading@10:  * @return 0 success, negative on error
yading@10:  */
yading@10: static av_cold int escape124_decode_init(AVCodecContext *avctx)
yading@10: {
yading@10:     Escape124Context *s = avctx->priv_data;
yading@10: 
yading@10:     avcodec_get_frame_defaults(&s->frame);
yading@10:     avctx->pix_fmt = AV_PIX_FMT_RGB555;
yading@10: 
yading@10:     s->num_superblocks = ((unsigned)avctx->width / 8) *
yading@10:                          ((unsigned)avctx->height / 8);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static av_cold int escape124_decode_close(AVCodecContext *avctx)
yading@10: {
yading@10:     unsigned i;
yading@10:     Escape124Context *s = avctx->priv_data;
yading@10: 
yading@10:     for (i = 0; i < 3; i++)
yading@10:         av_free(s->codebooks[i].blocks);
yading@10: 
yading@10:     av_frame_unref(&s->frame);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
yading@10:                                  unsigned size)
yading@10: {
yading@10:     unsigned i, j;
yading@10:     CodeBook cb = { 0 };
yading@10: 
yading@10:     if (!can_safely_read(gb, (uint64_t)size * 34))
yading@10:         return cb;
yading@10: 
yading@10:     if (size >= INT_MAX / sizeof(MacroBlock))
yading@10:         return cb;
yading@10:     cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
yading@10:     if (!cb.blocks)
yading@10:         return cb;
yading@10: 
yading@10:     cb.depth = depth;
yading@10:     cb.size = size;
yading@10:     for (i = 0; i < size; i++) {
yading@10:         unsigned mask_bits = get_bits(gb, 4);
yading@10:         unsigned color0 = get_bits(gb, 15);
yading@10:         unsigned color1 = get_bits(gb, 15);
yading@10: 
yading@10:         for (j = 0; j < 4; j++) {
yading@10:             if (mask_bits & (1 << j))
yading@10:                 cb.blocks[i].pixels[j] = color1;
yading@10:             else
yading@10:                 cb.blocks[i].pixels[j] = color0;
yading@10:         }
yading@10:     }
yading@10:     return cb;
yading@10: }
yading@10: 
yading@10: static unsigned decode_skip_count(GetBitContext* gb)
yading@10: {
yading@10:     unsigned value;
yading@10:     // This function reads a maximum of 23 bits,
yading@10:     // which is within the padding space
yading@10:     if (!can_safely_read(gb, 1))
yading@10:         return -1;
yading@10:     value = get_bits1(gb);
yading@10:     if (!value)
yading@10:         return value;
yading@10: 
yading@10:     value += get_bits(gb, 3);
yading@10:     if (value != (1 + ((1 << 3) - 1)))
yading@10:         return value;
yading@10: 
yading@10:     value += get_bits(gb, 7);
yading@10:     if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
yading@10:         return value;
yading@10: 
yading@10:     return value + get_bits(gb, 12);
yading@10: }
yading@10: 
yading@10: static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
yading@10:                                     int* codebook_index, int superblock_index)
yading@10: {
yading@10:     // This function reads a maximum of 22 bits; the callers
yading@10:     // guard this function appropriately
yading@10:     unsigned block_index, depth;
yading@10: 
yading@10:     if (get_bits1(gb)) {
yading@10:         static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
yading@10:         *codebook_index = transitions[*codebook_index][get_bits1(gb)];
yading@10:     }
yading@10: 
yading@10:     depth = s->codebooks[*codebook_index].depth;
yading@10: 
yading@10:     // depth = 0 means that this shouldn't read any bits;
yading@10:     // in theory, this is the same as get_bits(gb, 0), but
yading@10:     // that doesn't actually work.
yading@10:     block_index = depth ? get_bits(gb, depth) : 0;
yading@10: 
yading@10:     if (*codebook_index == 1) {
yading@10:         block_index += superblock_index << s->codebooks[1].depth;
yading@10:     }
yading@10: 
yading@10:     // This condition can occur with invalid bitstreams and
yading@10:     // *codebook_index == 2
yading@10:     if (block_index >= s->codebooks[*codebook_index].size)
yading@10:         return (MacroBlock) { { 0 } };
yading@10: 
yading@10:     return s->codebooks[*codebook_index].blocks[block_index];
yading@10: }
yading@10: 
yading@10: static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
yading@10:    // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
yading@10:    uint32_t *dst = sb->pixels32 + index + (index & -4);
yading@10: 
yading@10:    // This technically violates C99 aliasing rules, but it should be safe.
yading@10:    dst[0] = mb.pixels32[0];
yading@10:    dst[4] = mb.pixels32[1];
yading@10: }
yading@10: 
yading@10: static void copy_superblock(uint16_t* dest, unsigned dest_stride,
yading@10:                             uint16_t* src, unsigned src_stride)
yading@10: {
yading@10:     unsigned y;
yading@10:     if (src)
yading@10:         for (y = 0; y < 8; y++)
yading@10:             memcpy(dest + y * dest_stride, src + y * src_stride,
yading@10:                    sizeof(uint16_t) * 8);
yading@10:     else
yading@10:         for (y = 0; y < 8; y++)
yading@10:             memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
yading@10: }
yading@10: 
yading@10: static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
yading@10:                                        0x4,   0x8,   0x40,   0x80,
yading@10:                                        0x100, 0x200, 0x1000, 0x2000,
yading@10:                                        0x400, 0x800, 0x4000, 0x8000};
yading@10: 
yading@10: static int escape124_decode_frame(AVCodecContext *avctx,
yading@10:                                   void *data, int *got_frame,
yading@10:                                   AVPacket *avpkt)
yading@10: {
yading@10:     const uint8_t *buf = avpkt->data;
yading@10:     int buf_size = avpkt->size;
yading@10:     Escape124Context *s = avctx->priv_data;
yading@10:     AVFrame *frame = data;
yading@10: 
yading@10:     GetBitContext gb;
yading@10:     unsigned frame_flags, frame_size;
yading@10:     unsigned i;
yading@10: 
yading@10:     unsigned superblock_index, cb_index = 1,
yading@10:              superblock_col_index = 0,
yading@10:              superblocks_per_row = avctx->width / 8, skip = -1;
yading@10: 
yading@10:     uint16_t* old_frame_data, *new_frame_data;
yading@10:     unsigned old_stride, new_stride;
yading@10: 
yading@10:     int ret;
yading@10: 
yading@10:     init_get_bits(&gb, buf, buf_size * 8);
yading@10: 
yading@10:     // This call also guards the potential depth reads for the
yading@10:     // codebook unpacking.
yading@10:     if (!can_safely_read(&gb, 64))
yading@10:         return -1;
yading@10: 
yading@10:     frame_flags = get_bits_long(&gb, 32);
yading@10:     frame_size  = get_bits_long(&gb, 32);
yading@10: 
yading@10:     // Leave last frame unchanged
yading@10:     // FIXME: Is this necessary?  I haven't seen it in any real samples
yading@10:     if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
yading@10:         if (!s->frame.data[0])
yading@10:             return AVERROR_INVALIDDATA;
yading@10: 
yading@10:         av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
yading@10: 
yading@10:         *got_frame = 1;
yading@10:         if ((ret = av_frame_ref(frame, &s->frame)) < 0)
yading@10:             return ret;
yading@10: 
yading@10:         return frame_size;
yading@10:     }
yading@10: 
yading@10:     for (i = 0; i < 3; i++) {
yading@10:         if (frame_flags & (1 << (17 + i))) {
yading@10:             unsigned cb_depth, cb_size;
yading@10:             if (i == 2) {
yading@10:                 // This codebook can be cut off at places other than
yading@10:                 // powers of 2, leaving some of the entries undefined.
yading@10:                 cb_size = get_bits_long(&gb, 20);
yading@10:                 cb_depth = av_log2(cb_size - 1) + 1;
yading@10:             } else {
yading@10:                 cb_depth = get_bits(&gb, 4);
yading@10:                 if (i == 0) {
yading@10:                     // This is the most basic codebook: pow(2,depth) entries
yading@10:                     // for a depth-length key
yading@10:                     cb_size = 1 << cb_depth;
yading@10:                 } else {
yading@10:                     // This codebook varies per superblock
yading@10:                     // FIXME: I don't think this handles integer overflow
yading@10:                     // properly
yading@10:                     cb_size = s->num_superblocks << cb_depth;
yading@10:                 }
yading@10:             }
yading@10:             av_free(s->codebooks[i].blocks);
yading@10:             s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
yading@10:             if (!s->codebooks[i].blocks)
yading@10:                 return -1;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     new_frame_data = (uint16_t*)frame->data[0];
yading@10:     new_stride = frame->linesize[0] / 2;
yading@10:     old_frame_data = (uint16_t*)s->frame.data[0];
yading@10:     old_stride = s->frame.linesize[0] / 2;
yading@10: 
yading@10:     for (superblock_index = 0; superblock_index < s->num_superblocks;
yading@10:          superblock_index++) {
yading@10:         MacroBlock mb;
yading@10:         SuperBlock sb;
yading@10:         unsigned multi_mask = 0;
yading@10: 
yading@10:         if (skip == -1) {
yading@10:             // Note that this call will make us skip the rest of the blocks
yading@10:             // if the frame prematurely ends
yading@10:             skip = decode_skip_count(&gb);
yading@10:         }
yading@10: 
yading@10:         if (skip) {
yading@10:             copy_superblock(new_frame_data, new_stride,
yading@10:                             old_frame_data, old_stride);
yading@10:         } else {
yading@10:             copy_superblock(sb.pixels, 8,
yading@10:                             old_frame_data, old_stride);
yading@10: 
yading@10:             while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
yading@10:                 unsigned mask;
yading@10:                 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
yading@10:                 mask = get_bits(&gb, 16);
yading@10:                 multi_mask |= mask;
yading@10:                 for (i = 0; i < 16; i++) {
yading@10:                     if (mask & mask_matrix[i]) {
yading@10:                         insert_mb_into_sb(&sb, mb, i);
yading@10:                     }
yading@10:                 }
yading@10:             }
yading@10: 
yading@10:             if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
yading@10:                 unsigned inv_mask = get_bits(&gb, 4);
yading@10:                 for (i = 0; i < 4; i++) {
yading@10:                     if (inv_mask & (1 << i)) {
yading@10:                         multi_mask ^= 0xF << i*4;
yading@10:                     } else {
yading@10:                         multi_mask ^= get_bits(&gb, 4) << i*4;
yading@10:                     }
yading@10:                 }
yading@10: 
yading@10:                 for (i = 0; i < 16; i++) {
yading@10:                     if (multi_mask & mask_matrix[i]) {
yading@10:                         if (!can_safely_read(&gb, 1))
yading@10:                             break;
yading@10:                         mb = decode_macroblock(s, &gb, &cb_index,
yading@10:                                                superblock_index);
yading@10:                         insert_mb_into_sb(&sb, mb, i);
yading@10:                     }
yading@10:                 }
yading@10:             } else if (frame_flags & (1 << 16)) {
yading@10:                 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
yading@10:                     mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
yading@10:                     insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
yading@10:                 }
yading@10:             }
yading@10: 
yading@10:             copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
yading@10:         }
yading@10: 
yading@10:         superblock_col_index++;
yading@10:         new_frame_data += 8;
yading@10:         if (old_frame_data)
yading@10:             old_frame_data += 8;
yading@10:         if (superblock_col_index == superblocks_per_row) {
yading@10:             new_frame_data += new_stride * 8 - superblocks_per_row * 8;
yading@10:             if (old_frame_data)
yading@10:                 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
yading@10:             superblock_col_index = 0;
yading@10:         }
yading@10:         skip--;
yading@10:     }
yading@10: 
yading@10:     av_log(NULL, AV_LOG_DEBUG,
yading@10:            "Escape sizes: %i, %i, %i\n",
yading@10:            frame_size, buf_size, get_bits_count(&gb) / 8);
yading@10: 
yading@10:     av_frame_unref(&s->frame);
yading@10:     if ((ret = av_frame_ref(&s->frame, frame)) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     *got_frame = 1;
yading@10: 
yading@10:     return frame_size;
yading@10: }
yading@10: 
yading@10: 
yading@10: AVCodec ff_escape124_decoder = {
yading@10:     .name           = "escape124",
yading@10:     .type           = AVMEDIA_TYPE_VIDEO,
yading@10:     .id             = AV_CODEC_ID_ESCAPE124,
yading@10:     .priv_data_size = sizeof(Escape124Context),
yading@10:     .init           = escape124_decode_init,
yading@10:     .close          = escape124_decode_close,
yading@10:     .decode         = escape124_decode_frame,
yading@10:     .capabilities   = CODEC_CAP_DR1,
yading@10:     .long_name      = NULL_IF_CONFIG_SMALL("Escape 124"),
yading@10: };