Escape 124 (RPL) decoder

Patch by Eli Friedman (eli friedman gmail com)

Originally committed as revision 12648 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/Makefile

@@ -67,6 +67,7 @@ OBJS-$(CONFIG_DXA_DECODER)             += dxa.o
 OBJS-$(CONFIG_EIGHTBPS_DECODER)        += 8bps.o
 OBJS-$(CONFIG_EIGHTSVX_EXP_DECODER)    += 8svx.o
 OBJS-$(CONFIG_EIGHTSVX_FIB_DECODER)    += 8svx.o
+OBJS-$(CONFIG_ESCAPE124_DECODER)       += escape124.o
 OBJS-$(CONFIG_FFV1_DECODER)            += ffv1.o rangecoder.o golomb.o
 OBJS-$(CONFIG_FFV1_ENCODER)            += ffv1.o rangecoder.o
 OBJS-$(CONFIG_FFVHUFF_DECODER)         += huffyuv.o

libavcodec/allcodecs.c

@@ -80,6 +80,7 @@ void avcodec_register_all(void)
     REGISTER_DECODER (EIGHTBPS, eightbps);
     REGISTER_DECODER (EIGHTSVX_EXP, eightsvx_exp);
     REGISTER_DECODER (EIGHTSVX_FIB, eightsvx_fib);
+    REGISTER_DECODER (ESCAPE124, escape124);
     REGISTER_ENCDEC  (FFV1, ffv1);
     REGISTER_ENCDEC  (FFVHUFF, ffvhuff);
     REGISTER_ENCDEC  (FLASHSV, flashsv);

libavcodec/avcodec.h

@@ -181,6 +181,7 @@ enum CodecID {
     CODEC_ID_RL2,
     CODEC_ID_8SVX_EXP,
     CODEC_ID_8SVX_FIB,
+    CODEC_ID_ESCAPE124,
 
     /* various PCM "codecs" */
     CODEC_ID_PCM_S16LE= 0x10000,

libavcodec/escape124.c

@@ -0,0 +1,384 @@
+/*
+ * 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,
+};
+