MSS2 decoder

Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>

1 files changed, 860 insertions, 0 deletions

diff --git a/libavcodec/mss2.c b/libavcodec/mss2.c
new file mode 100644
index 0000000000..c0c47dc8d3
--- /dev/null
+++ b/libavcodec/mss2.c
@@ -0,0 +1,860 @@
+/*
+ * Microsoft Screen 2 (aka Windows Media Video V9 Screen) decoder
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Microsoft Screen 2 (aka Windows Media Video V9 Screen) decoder
+ */
+
+#include "libavutil/avassert.h"
+#include "msmpeg4data.h"
+#include "vc1.h"
+#include "mss12.h"
+#include "mss2dsp.h"
+
+typedef struct MSS2Context {
+    VC1Context     v;
+    int            split_position;
+    AVFrame        pic;
+    AVFrame        last_pic;
+    MSS12Context   c;
+    MSS2DSPContext dsp;
+    SliceContext   sc[2];
+} MSS2Context;
+
+static void arith2_normalise(ArithCoder *c)
+{
+    while ((c->high >> 15) - (c->low >> 15) < 2) {
+        if ((c->low ^ c->high) & 0x10000) {
+            c->high  ^= 0x8000;
+            c->value ^= 0x8000;
+            c->low   ^= 0x8000;
+        }
+        c->high  = c->high  << 8 & 0xFFFFFF | 0xFF;
+        c->value = c->value << 8 & 0xFFFFFF | bytestream2_get_byte(c->gbc.gB);
+        c->low   = c->low   << 8 & 0xFFFFFF;
+    }
+}
+
+ARITH_GET_BIT(2)
+
+/* L. Stuiver and A. Moffat: "Piecewise Integer Mapping for Arithmetic Coding."
+ * In Proc. 8th Data Compression Conference (DCC '98), pp. 3-12, Mar. 1998 */
+
+static int arith2_get_scaled_value(int value, int n, int range)
+{
+    int split = (n << 1) - range;
+
+    if (value > split)
+        return split + (value - split >> 1);
+    else
+        return value;
+}
+
+static void arith2_rescale_interval(ArithCoder *c, int range,
+                                    int low, int high, int n)
+{
+    int split = (n << 1) - range;
+
+    if (high > split)
+        c->high = split + (high - split << 1);
+    else
+        c->high = high;
+
+    c->high += c->low - 1;
+
+    if (low > split)
+        c->low += split + (low - split << 1);
+    else
+        c->low += low;
+}
+
+static int arith2_get_number(ArithCoder *c, int n)
+{
+    int range = c->high - c->low + 1;
+    int scale = av_log2(range) - av_log2(n);
+    int val;
+
+    if (n << scale > range)
+        scale--;
+
+    n <<= scale;
+
+    val = arith2_get_scaled_value(c->value - c->low, n, range) >> scale;
+
+    arith2_rescale_interval(c, range, val << scale, (val + 1) << scale, n);
+
+    arith2_normalise(c);
+
+    return val;
+}
+
+static int arith2_get_prob(ArithCoder *c, int *probs)
+{
+    int range = c->high - c->low + 1, n = *probs;
+    int scale = av_log2(range) - av_log2(n);
+    int i     = 0, val;
+
+    if (n << scale > range)
+        scale--;
+
+    n <<= scale;
+
+    val = arith2_get_scaled_value(c->value - c->low, n, range) >> scale;
+    while (probs[++i] > val) ;
+
+    arith2_rescale_interval(c, range,
+                            probs[i] << scale, probs[i - 1] << scale, n);
+
+    return i;
+}
+
+ARITH_GET_MODEL_SYM(2)
+
+static int arith2_get_consumed_bytes(ArithCoder *c)
+{
+    int diff = (c->high >> 16) - (c->low >> 16);
+    int bp   = bytestream2_tell(c->gbc.gB) - 3 << 3;
+    int bits = 1;
+
+    while (!(diff & 0x80)) {
+        bits++;
+        diff <<= 1;
+    }
+
+    return (bits + bp + 7 >> 3) + ((c->low >> 16) + 1 == c->high >> 16);
+}
+
+static void arith2_init(ArithCoder *c, GetByteContext *gB)
+{
+    c->low           = 0;
+    c->high          = 0xFFFFFF;
+    c->value         = bytestream2_get_be24(gB);
+    c->gbc.gB        = gB;
+    c->get_model_sym = arith2_get_model_sym;
+    c->get_number    = arith2_get_number;
+}
+
+static int decode_pal_v2(MSS12Context *ctx, const uint8_t *buf, int buf_size)
+{
+    int i, ncol;
+    uint32_t *pal = ctx->pal + 256 - ctx->free_colours;
+
+    if (!ctx->free_colours)
+        return 0;
+
+    ncol = *buf++;
+    if (buf_size < 2 + ncol * 3)
+        return -1;
+    for (i = 0; i < ncol; i++)
+        *pal++ = AV_RB24(buf + 3 * i);
+
+    return 1 + ncol * 3;
+}
+
+static int decode_555(GetByteContext *gB, uint16_t *dst, int stride,
+                      int keyframe, int w, int h)
+{
+    int last_symbol = 0, repeat = 0, prev_avail = 0;
+
+    if (!keyframe) {
+        int x, y, endx, endy, t;
+
+#define READ_PAIR(a, b)                 \
+    a  = bytestream2_get_byte(gB) << 4; \
+    t  = bytestream2_get_byte(gB);      \
+    a |= t >> 4;                        \
+    b  = (t & 0xF) << 8;                \
+    b |= bytestream2_get_byte(gB);      \
+
+        READ_PAIR(x, endx)
+        READ_PAIR(y, endy)
+
+        if (endx >= w || endy >= h || x > endx || y > endy)
+            return -1;
+        dst += x + stride * y;
+        w    = endx - x + 1;
+        h    = endy - y + 1;
+        if (y)
+            prev_avail = 1;
+    }
+
+    do {
+        uint16_t *p = dst;
+        do {
+            if (repeat-- < 1) {
+                int b = bytestream2_get_byte(gB);
+                if (b < 128)
+                    last_symbol = b << 8 | bytestream2_get_byte(gB);
+                else if (b > 129) {
+                    repeat = 0;
+                    while (b-- > 130)
+                        repeat = (repeat << 8) + bytestream2_get_byte(gB) + 1;
+                    if (last_symbol == -2) {
+                        int skip = FFMIN((unsigned)repeat, dst + w - p);
+                        repeat -= skip;
+                        p      += skip;
+                    }
+                } else
+                    last_symbol = 127 - b;
+            }
+            if (last_symbol >= 0)
+                *p = last_symbol;
+            else if (last_symbol == -1 && prev_avail)
+                *p = *(p - stride);
+        } while (++p < dst + w);
+        dst       += stride;
+        prev_avail = 1;
+    } while (--h);
+
+    return 0;
+}
+
+static int decode_rle(GetBitContext *gb, uint8_t *pal_dst, int pal_stride,
+                      uint8_t *rgb_dst, int rgb_stride, uint32_t *pal,
+                      int keyframe, int kf_slipt, int slice, int w, int h)
+{
+    uint8_t bits[270] = { 0 };
+    uint32_t codes[270];
+    VLC vlc;
+
+    int current_length = 0, read_codes = 0, next_code = 0, current_codes = 0;
+    int remaining_codes, surplus_codes, i;
+
+    const int alphabet_size = 270 - keyframe;
+
+    int last_symbol = 0, repeat = 0, prev_avail = 0;
+
+    if (!keyframe) {
+        int x, y, clipw, cliph;
+
+        x     = get_bits(gb, 12);
+        y     = get_bits(gb, 12);
+        clipw = get_bits(gb, 12) + 1;
+        cliph = get_bits(gb, 12) + 1;
+
+        if (x + clipw > w || y + cliph > h)
+            return AVERROR_INVALIDDATA;
+        pal_dst += pal_stride * y + x;
+        rgb_dst += rgb_stride * y + x * 3;
+        w        = clipw;
+        h        = cliph;
+        if (y)
+            prev_avail = 1;
+    } else {
+        if (slice > 0) {
+            pal_dst   += pal_stride * kf_slipt;
+            rgb_dst   += rgb_stride * kf_slipt;
+            prev_avail = 1;
+            h         -= kf_slipt;
+        } else
+            h = kf_slipt;
+    }
+
+    /* read explicit codes */
+    do {
+        while (current_codes--) {
+            int symbol = get_bits(gb, 8);
+            if (symbol >= 204 - keyframe)
+                symbol += 14 - keyframe;
+            else if (symbol > 189)
+                symbol = get_bits1(gb) + (symbol << 1) - 190;
+            if (bits[symbol])
+                return AVERROR_INVALIDDATA;
+            bits[symbol]  = current_length;
+            codes[symbol] = next_code++;
+            read_codes++;
+        }
+        current_length++;
+        next_code     <<= 1;
+        remaining_codes = (1 << current_length) - next_code;
+        current_codes   = get_bits(gb, av_ceil_log2(remaining_codes + 1));
+        if (current_length > 22 || current_codes > remaining_codes)
+            return AVERROR_INVALIDDATA;
+    } while (current_codes != remaining_codes);
+
+    remaining_codes = alphabet_size - read_codes;
+
+    /* determine the minimum length to fit the rest of the alphabet */
+    while ((surplus_codes = (2 << current_length) -
+                            (next_code << 1) - remaining_codes) < 0) {
+        current_length++;
+        next_code <<= 1;
+    }
+
+    /* add the rest of the symbols lexicographically */
+    for (i = 0; i < alphabet_size; i++)
+        if (!bits[i]) {
+            if (surplus_codes-- == 0) {
+                current_length++;
+                next_code <<= 1;
+            }
+            bits[i]  = current_length;
+            codes[i] = next_code++;
+        }
+
+    if (next_code != 1 << current_length)
+        return AVERROR_INVALIDDATA;
+
+    if (i = init_vlc(&vlc, 9, alphabet_size, bits, 1, 1, codes, 4, 4, 0))
+        return i;
+
+    /* frame decode */
+    do {
+        uint8_t *pp = pal_dst;
+        uint8_t *rp = rgb_dst;
+        do {
+            if (repeat-- < 1) {
+                int b = get_vlc2(gb, vlc.table, 9, 3);
+                if (b < 256)
+                    last_symbol = b;
+                else if (b < 268) {
+                    b -= 256;
+                    if (b == 11)
+                        b = get_bits(gb, 4) + 10;
+
+                    if (!b)
+                        repeat = 0;
+                    else
+                        repeat = get_bits(gb, b);
+
+                    while (b--)
+                        repeat += 1 << b;
+
+                    if (last_symbol == -2) {
+                        int skip = FFMIN(repeat, pal_dst + w - pp);
+                        repeat -= skip;
+                        pp     += skip;
+                        rp     += skip * 3;
+                    }
+                } else
+                    last_symbol = 267 - b;
+            }
+            if (last_symbol >= 0) {
+                *pp = last_symbol;
+                AV_WB24(rp, pal[last_symbol]);
+            } else if (last_symbol == -1 && prev_avail) {
+                *pp = *(pp - pal_stride);
+                memcpy(rp, rp - rgb_stride, 3);
+            }
+            rp += 3;
+        } while (++pp < pal_dst + w);
+        pal_dst   += pal_stride;
+        rgb_dst   += rgb_stride;
+        prev_avail = 1;
+    } while (--h);
+
+    ff_free_vlc(&vlc);
+    return 0;
+}
+
+static int decode_wmv9(AVCodecContext *avctx, const uint8_t *buf, int buf_size,
+                       int x, int y, int w, int h, int wmv9_mask)
+{
+    MSS2Context *ctx  = avctx->priv_data;
+    MSS12Context *c   = &ctx->c;
+    VC1Context *v     = avctx->priv_data;
+    MpegEncContext *s = &v->s;
+    AVFrame *f;
+
+    ff_mpeg_flush(avctx);
+
+    if (s->current_picture_ptr == NULL || s->current_picture_ptr->f.data[0]) {
+        int i = ff_find_unused_picture(s, 0);
+        if (i < 0)
+            return -1;
+        s->current_picture_ptr = &s->picture[i];
+    }
+
+    init_get_bits(&s->gb, buf, buf_size * 8);
+
+    s->loop_filter = avctx->skip_loop_filter < AVDISCARD_ALL;
+
+    if (ff_vc1_parse_frame_header(v, &s->gb) == -1) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "header error\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (s->pict_type != AV_PICTURE_TYPE_I) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "expected I-frame\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    avctx->pix_fmt = PIX_FMT_YUV420P;
+
+    if (ff_MPV_frame_start(s, avctx) < 0) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "ff_MPV_frame_start error\n");
+        avctx->pix_fmt = PIX_FMT_RGB24;
+        return -1;
+    }
+
+    ff_er_frame_start(s);
+
+    v->bits = buf_size * 8;
+
+    v->end_mb_x = (w + 15) >> 4;
+    s->end_mb_y = (h + 15) >> 4;
+    if (v->respic & 1)
+        v->end_mb_x = v->end_mb_x + 1 >> 1;
+    if (v->respic & 2)
+        s->end_mb_y = s->end_mb_y + 1 >> 1;
+
+    ff_vc1_decode_blocks(v);
+
+    ff_er_frame_end(s);
+
+    ff_MPV_frame_end(s);
+
+    f = &s->current_picture.f;
+
+    if (v->respic == 3) {
+        ctx->dsp.upsample_plane(f->data[0], f->linesize[0], w,      h);
+        ctx->dsp.upsample_plane(f->data[1], f->linesize[1], w >> 1, h >> 1);
+        ctx->dsp.upsample_plane(f->data[2], f->linesize[2], w >> 1, h >> 1);
+    } else if (v->respic)
+        av_log_ask_for_sample(v->s.avctx,
+                              "Asymmetric WMV9 rectangle subsampling\n");
+
+    av_assert0(f->linesize[1] == f->linesize[2]);
+
+    if (wmv9_mask != -1)
+        ctx->dsp.mss2_blit_wmv9_masked(c->rgb_pic + y * c->rgb_stride + x * 3,
+                                       c->rgb_stride, wmv9_mask,
+                                       c->pal_pic + y * c->pal_stride + x,
+                                       c->pal_stride,
+                                       f->data[0], f->linesize[0],
+                                       f->data[1], f->data[2], f->linesize[1],
+                                       w, h);
+    else
+        ctx->dsp.mss2_blit_wmv9(c->rgb_pic + y * c->rgb_stride + x * 3,
+                                c->rgb_stride,
+                                f->data[0], f->linesize[0],
+                                f->data[1], f->data[2], f->linesize[1],
+                                w, h);
+
+    avctx->pix_fmt = PIX_FMT_RGB24;
+
+    return 0;
+}
+
+typedef struct Rectangle {
+    int coded, x, y, w, h;
+} Rectangle;
+
+#define MAX_WMV9_RECTANGLES 20
+#define ARITH2_PADDING 2
+
+static int mss2_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
+                             AVPacket *avpkt)
+{
+    const uint8_t *buf = avpkt->data;
+    int buf_size       = avpkt->size;
+    MSS2Context *ctx = avctx->priv_data;
+    MSS12Context *c  = &ctx->c;
+    GetBitContext gb;
+    GetByteContext gB;
+    ArithCoder acoder;
+
+    int keyframe, has_wmv9, has_mv, is_rle, is_555, ret;
+
+    Rectangle wmv9rects[MAX_WMV9_RECTANGLES], *r;
+    int used_rects = 0, i, implicit_rect, av_uninit(wmv9_mask);
+
+    av_assert0(FF_INPUT_BUFFER_PADDING_SIZE >=
+               ARITH2_PADDING + (MIN_CACHE_BITS + 7) / 8);
+
+    init_get_bits(&gb, buf, buf_size * 8);
+
+    if (keyframe = get_bits1(&gb))
+        skip_bits(&gb, 7);
+    has_wmv9 = get_bits1(&gb);
+    has_mv   = keyframe ? 0 : get_bits1(&gb);
+    is_rle   = get_bits1(&gb);
+    is_555   = is_rle && get_bits1(&gb);
+    if (c->slice_split > 0)
+        ctx->split_position = c->slice_split;
+    else if (c->slice_split < 0) {
+        if (get_bits1(&gb)) {
+            if (get_bits1(&gb)) {
+                if (get_bits1(&gb))
+                    ctx->split_position = get_bits(&gb, 16);
+                else
+                    ctx->split_position = get_bits(&gb, 12);
+            } else
+                ctx->split_position = get_bits(&gb, 8) << 4;
+        } else {
+            if (keyframe)
+                ctx->split_position = avctx->height / 2;
+        }
+    } else
+        ctx->split_position = avctx->height;
+
+    if (c->slice_split && (ctx->split_position < 1 - is_555 ||
+                           ctx->split_position > avctx->height - 1))
+        return AVERROR_INVALIDDATA;
+
+    align_get_bits(&gb);
+    buf      += get_bits_count(&gb) >> 3;
+    buf_size -= get_bits_count(&gb) >> 3;
+
+    if (buf_size < 1)
+        return AVERROR_INVALIDDATA;
+
+    if (is_555 && (has_wmv9 || has_mv || c->slice_split && ctx->split_position))
+        return AVERROR_INVALIDDATA;
+
+    avctx->pix_fmt = is_555 ? PIX_FMT_RGB555 : PIX_FMT_RGB24;
+    if (ctx->pic.data[0] && ctx->pic.format != avctx->pix_fmt)
+        avctx->release_buffer(avctx, &ctx->pic);
+
+    if (has_wmv9) {
+        bytestream2_init(&gB, buf, buf_size + ARITH2_PADDING);
+        arith2_init(&acoder, &gB);
+
+        implicit_rect = !arith2_get_bit(&acoder);
+
+        while (arith2_get_bit(&acoder)) {
+            if (used_rects == MAX_WMV9_RECTANGLES)
+                return AVERROR_INVALIDDATA;
+            r = &wmv9rects[used_rects];
+            if (!used_rects)
+                r->x = arith2_get_number(&acoder, avctx->width);
+            else
+                r->x = arith2_get_number(&acoder, avctx->width -
+                                         wmv9rects[used_rects - 1].x) +
+                       wmv9rects[used_rects - 1].x;
+            r->y = arith2_get_number(&acoder, avctx->height);
+            r->w = arith2_get_number(&acoder, avctx->width  - r->x) + 1;
+            r->h = arith2_get_number(&acoder, avctx->height - r->y) + 1;
+            used_rects++;
+        }
+
+        if (implicit_rect && used_rects) {
+            av_log(avctx, AV_LOG_ERROR, "implicit_rect && used_rects > 0\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        if (implicit_rect) {
+            wmv9rects[0].x = 0;
+            wmv9rects[0].y = 0;
+            wmv9rects[0].w = avctx->width;
+            wmv9rects[0].h = avctx->height;
+
+            used_rects = 1;
+        }
+        for (i = 0; i < used_rects; i++) {
+            if (!implicit_rect && arith2_get_bit(&acoder)) {
+                av_log(avctx, AV_LOG_ERROR, "Unexpected grandchildren\n");
+                return AVERROR_INVALIDDATA;
+            }
+            if (!i) {
+                wmv9_mask = arith2_get_bit(&acoder) - 1;
+                if (!wmv9_mask)
+                    wmv9_mask = arith2_get_number(&acoder, 256);
+            }
+            wmv9rects[i].coded = arith2_get_number(&acoder, 2);
+        }
+
+        buf      += arith2_get_consumed_bytes(&acoder);
+        buf_size -= arith2_get_consumed_bytes(&acoder);
+        if (buf_size < 1)
+            return AVERROR_INVALIDDATA;
+    }
+
+    c->mvX = c->mvY = 0;
+    if (keyframe && !is_555) {
+        if ((i = decode_pal_v2(c, buf, buf_size)) < 0)
+            return AVERROR_INVALIDDATA;
+        buf      += i;
+        buf_size -= i;
+    } else if (has_mv) {
+        buf      += 4;
+        buf_size -= 4;
+        if (buf_size < 1)
+            return AVERROR_INVALIDDATA;
+        c->mvX = AV_RB16(buf - 4) - avctx->width;
+        c->mvY = AV_RB16(buf - 2) - avctx->height;
+    }
+
+    if (c->mvX < 0 || c->mvY < 0) {
+        FFSWAP(AVFrame, ctx->pic, ctx->last_pic);
+        FFSWAP(uint8_t *, c->pal_pic, c->last_pal_pic);
+
+        if (ctx->pic.data[0])
+            avctx->release_buffer(avctx, &ctx->pic);
+
+        ctx->pic.reference    = 3;
+        ctx->pic.buffer_hints = FF_BUFFER_HINTS_VALID    |
+                                FF_BUFFER_HINTS_READABLE |
+                                FF_BUFFER_HINTS_PRESERVE |
+                                FF_BUFFER_HINTS_REUSABLE;
+
+        if ((ret = avctx->get_buffer(avctx, &ctx->pic)) < 0) {
+            av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
+            return ret;
+        }
+
+        if (ctx->last_pic.data[0]) {
+            av_assert0(ctx->pic.linesize[0] == ctx->last_pic.linesize[0]);
+            c->last_rgb_pic = ctx->last_pic.data[0] +
+                              ctx->last_pic.linesize[0] * (avctx->height - 1);
+        } else {
+            av_log(avctx, AV_LOG_ERROR, "Missing keyframe\n");
+            return -1;
+        }
+    } else {
+        if (ctx->last_pic.data[0])
+            avctx->release_buffer(avctx, &ctx->last_pic);
+
+        ctx->pic.reference    = 3;
+        ctx->pic.buffer_hints = FF_BUFFER_HINTS_VALID    |
+                                FF_BUFFER_HINTS_READABLE |
+                                FF_BUFFER_HINTS_PRESERVE |
+                                FF_BUFFER_HINTS_REUSABLE;
+
+        if ((ret = avctx->reget_buffer(avctx, &ctx->pic)) < 0) {
+            av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
+            return ret;
+        }
+
+        c->last_rgb_pic = NULL;
+    }
+    c->rgb_pic    = ctx->pic.data[0] +
+                    ctx->pic.linesize[0] * (avctx->height - 1);
+    c->rgb_stride = -ctx->pic.linesize[0];
+
+    ctx->pic.key_frame = keyframe;
+    ctx->pic.pict_type = keyframe ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
+
+    if (is_555) {
+        bytestream2_init(&gB, buf, buf_size);
+
+        if (decode_555(&gB, (uint16_t *)c->rgb_pic, c->rgb_stride >> 1,
+                       keyframe, avctx->width, avctx->height))
+            return AVERROR_INVALIDDATA;
+
+        buf_size -= bytestream2_tell(&gB);
+    } else if (is_rle) {
+        init_get_bits(&gb, buf, buf_size * 8);
+        if (ret = decode_rle(&gb, c->pal_pic, c->pal_stride,
+                             c->rgb_pic, c->rgb_stride, c->pal, keyframe,
+                             ctx->split_position, 0,
+                             avctx->width, avctx->height))
+            return ret;
+        align_get_bits(&gb);
+
+        if (c->slice_split)
+            if (ret = decode_rle(&gb, c->pal_pic, c->pal_stride,
+                                 c->rgb_pic, c->rgb_stride, c->pal, keyframe,
+                                 ctx->split_position, 1,
+                                 avctx->width, avctx->height))
+                return ret;
+
+        align_get_bits(&gb);
+        buf      += get_bits_count(&gb) >> 3;
+        buf_size -= get_bits_count(&gb) >> 3;
+    } else {
+        if (keyframe)
+            ff_mss12_codec_reset(c);
+        else if (c->corrupted)
+            return AVERROR_INVALIDDATA;
+        bytestream2_init(&gB, buf, buf_size + ARITH2_PADDING);
+        arith2_init(&acoder, &gB);
+        c->keyframe = keyframe;
+        if (c->corrupted = ff_mss12_decode_rect(&c->sc[0], &acoder, 0, 0,
+                                                avctx->width,
+                                                ctx->split_position))
+            return AVERROR_INVALIDDATA;
+
+        buf      += arith2_get_consumed_bytes(&acoder);
+        buf_size -= arith2_get_consumed_bytes(&acoder);
+        if (c->slice_split) {
+            if (buf_size < 1)
+                return AVERROR_INVALIDDATA;
+            bytestream2_init(&gB, buf, buf_size + ARITH2_PADDING);
+            arith2_init(&acoder, &gB);
+            if (c->corrupted = ff_mss12_decode_rect(&c->sc[1], &acoder, 0,
+                                                    ctx->split_position,
+                                                    avctx->width,
+                                                    avctx->height - ctx->split_position))
+                return AVERROR_INVALIDDATA;
+
+            buf      += arith2_get_consumed_bytes(&acoder);
+            buf_size -= arith2_get_consumed_bytes(&acoder);
+        }
+    }
+
+    if (has_wmv9) {
+        for (i = 0; i < used_rects; i++) {
+            int x = wmv9rects[i].x;
+            int y = wmv9rects[i].y;
+            int w = wmv9rects[i].w;
+            int h = wmv9rects[i].h;
+            if (wmv9rects[i].coded) {
+                int WMV9codedFrameSize;
+                if (buf_size < 4 || !(WMV9codedFrameSize = AV_RL24(buf)))
+                    return AVERROR_INVALIDDATA;
+                if (ret = decode_wmv9(avctx, buf + 3, buf_size - 3,
+                                      x, y, w, h, wmv9_mask))
+                    return ret;
+                buf      += WMV9codedFrameSize + 3;
+                buf_size -= WMV9codedFrameSize + 3;
+            } else {
+                uint8_t *dst = c->rgb_pic + y * c->rgb_stride + x * 3;
+                if (wmv9_mask != -1) {
+                    ctx->dsp.mss2_gray_fill_masked(dst, c->rgb_stride,
+                                                   wmv9_mask,
+                                                   c->pal_pic + y * c->pal_stride + x,
+                                                   c->pal_stride,
+                                                   w, h);
+                } else {
+                    do {
+                        memset(dst, 0x80, w * 3);
+                        dst += c->rgb_stride;
+                    } while (--h);
+                }
+            }
+        }
+    }
+
+    if (buf_size)
+        av_log(avctx, AV_LOG_WARNING, "buffer not fully consumed\n");
+
+    *data_size       = sizeof(AVFrame);
+    *(AVFrame *)data = ctx->pic;
+
+    return avpkt->size;
+}
+
+static av_cold int wmv9_init(AVCodecContext *avctx)
+{
+    VC1Context *v = avctx->priv_data;
+
+    v->s.avctx    = avctx;
+    avctx->flags |= CODEC_FLAG_EMU_EDGE;
+    v->s.flags   |= CODEC_FLAG_EMU_EDGE;
+
+    if (avctx->idct_algo == FF_IDCT_AUTO)
+        avctx->idct_algo = FF_IDCT_WMV2;
+
+    if (ff_vc1_init_common(v) < 0)
+        return -1;
+    ff_vc1dsp_init(&v->vc1dsp);
+
+    v->profile = PROFILE_MAIN;
+
+    v->zz_8x4     = ff_wmv2_scantableA;
+    v->zz_4x8     = ff_wmv2_scantableB;
+    v->res_y411   = 0;
+    v->res_sprite = 0;
+
+    v->frmrtq_postproc = 7;
+    v->bitrtq_postproc = 31;
+
+    v->res_x8          = 0;
+    v->multires        = 0;
+    v->res_fasttx      = 1;
+
+    v->fastuvmc        = 0;
+
+    v->extended_mv     = 0;
+
+    v->dquant          = 1;
+    v->vstransform     = 1;
+
+    v->res_transtab    = 0;
+
+    v->overlap         = 0;
+
+    v->s.resync_marker = 0;
+    v->rangered        = 0;
+
+    v->s.max_b_frames = avctx->max_b_frames = 0;
+    v->quantizer_mode = 0;
+
+    v->finterpflag = 0;
+
+    v->res_rtm_flag = 1;
+
+    ff_vc1_init_transposed_scantables(v);
+
+    if (ff_msmpeg4_decode_init(avctx) < 0 ||
+        ff_vc1_decode_init_alloc_tables(v) < 0)
+        return -1;
+
+    /* error concealment */
+    v->s.me.qpel_put = v->s.dsp.put_qpel_pixels_tab;
+    v->s.me.qpel_avg = v->s.dsp.avg_qpel_pixels_tab;
+
+    return 0;
+}
+
+static av_cold int mss2_decode_end(AVCodecContext *avctx)
+{
+    MSS2Context *const ctx = avctx->priv_data;
+
+    if (ctx->pic.data[0])
+        avctx->release_buffer(avctx, &ctx->pic);
+    if (ctx->last_pic.data[0])
+        avctx->release_buffer(avctx, &ctx->last_pic);
+
+    ff_mss12_decode_end(&ctx->c);
+    av_freep(&ctx->c.pal_pic);
+    av_freep(&ctx->c.last_pal_pic);
+    ff_vc1_decode_end(avctx);
+
+    return 0;
+}
+
+static av_cold int mss2_decode_init(AVCodecContext *avctx)
+{
+    MSS2Context * const ctx = avctx->priv_data;
+    MSS12Context *c = &ctx->c;
+    int ret;
+    c->avctx = avctx;
+    avctx->coded_frame = &ctx->pic;
+    if (ret = ff_mss12_decode_init(c, 1))
+        return ret;
+    c->pal_stride   = c->mask_stride;
+    c->pal_pic      = av_malloc(c->pal_stride * avctx->height);
+    c->last_pal_pic = av_malloc(c->pal_stride * avctx->height);
+    if (!c->pal_pic || !c->last_pal_pic) {
+        mss2_decode_end(avctx);
+        return AVERROR(ENOMEM);
+    }
+    if (ret = wmv9_init(avctx)) {
+        mss2_decode_end(avctx);
+        return ret;
+    }
+    ff_mss2dsp_init(&ctx->dsp);
+    return 0;
+}
+
+AVCodec ff_mss2_decoder = {
+    .name           = "mss2",
+    .type           = AVMEDIA_TYPE_VIDEO,
+    .id             = AV_CODEC_ID_MSS2,
+    .priv_data_size = sizeof(MSS2Context),
+    .init           = mss2_decode_init,
+    .close          = mss2_decode_end,
+    .decode         = mss2_decode_frame,
+    .capabilities   = CODEC_CAP_DR1,
+    .long_name      = NULL_IF_CONFIG_SMALL("MS Windows Media Video V9 Screen"),
+};