avcodec: add ScreenPressor decoder

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 813 insertions, 0 deletions

diff --git a/libavcodec/scpr.c b/libavcodec/scpr.c
new file mode 100644
index 0000000000..f53f1d4039
--- /dev/null
+++ b/libavcodec/scpr.c
@@ -0,0 +1,813 @@
+/*
+ * ScreenPressor decoder
+ *
+ * Copyright (c) 2017 Paul B Mahol
+ *
+ * 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "avcodec.h"
+#include "bytestream.h"
+#include "internal.h"
+
+#define TOP  0x01000000
+#define BOT    0x010000
+
+typedef struct RangeCoder {
+    unsigned   code;
+    unsigned   range;
+} RangeCoder;
+
+typedef struct PixelModel {
+    unsigned    freq[256];
+    unsigned    lookup[16];
+    unsigned    total_freq;
+} PixelModel;
+
+typedef struct SCPRContext {
+    AVFrame        *last_frame;
+    AVFrame        *current_frame;
+    GetByteContext  gb;
+    RangeCoder      rc;
+    PixelModel      pixel_model[3][4096];
+    unsigned        op_model[6][7];
+    unsigned        run_model[6][257];
+    unsigned        range_model[257];
+    unsigned        count_model[257];
+    unsigned        fill_model[6];
+    unsigned        sxy_model[4][17];
+    unsigned        mv_model[2][513];
+    unsigned        nbx, nby;
+    unsigned        nbcount;
+    unsigned       *blocks;
+    int             cxshift;
+} SCPRContext;
+
+static void init_rangecoder(RangeCoder *rc, GetByteContext *gb)
+{
+    rc->range = 0xFFFFFFFFU;
+    rc->code  = bytestream2_get_be32(gb);
+}
+
+static void reinit_tables(SCPRContext *s)
+{
+    int comp, i, j;
+
+    for (comp = 0; comp < 3; comp++) {
+        for (j = 0; j < 4096; j++) {
+            if (s->pixel_model[comp][j].total_freq != 256) {
+                for (i = 0; i < 256; i++)
+                    s->pixel_model[comp][j].freq[i] = 1;
+                for (i = 0; i < 16; i++)
+                    s->pixel_model[comp][j].lookup[i] = 16;
+                s->pixel_model[comp][j].total_freq = 256;
+            }
+        }
+    }
+
+    for (j = 0; j < 6; j++) {
+        unsigned *p = s->run_model[j];
+        for (i = 0; i < 256; i++)
+            p[i] = 1;
+        p[256] = 256;
+    }
+
+    for (j = 0; j < 6; j++) {
+        unsigned *op = s->op_model[j];
+        for (i = 0; i < 6; i++)
+            op[i] = 1;
+        op[6] = 6;
+    }
+
+    for (i = 0; i < 256; i++) {
+        s->range_model[i] = 1;
+        s->count_model[i] = 1;
+    }
+    s->range_model[256] = 256;
+    s->count_model[256] = 256;
+
+    for (i = 0; i < 5; i++) {
+        s->fill_model[i] = 1;
+    }
+    s->fill_model[5] = 5;
+
+    for (j = 0; j < 4; j++) {
+        for (i = 0; i < 16; i++) {
+            s->sxy_model[j][i] = 1;
+        }
+        s->sxy_model[j][16] = 16;
+    }
+
+    for (i = 0; i < 512; i++) {
+        s->mv_model[0][i] = 1;
+        s->mv_model[1][i] = 1;
+    }
+    s->mv_model[0][512] = 512;
+    s->mv_model[1][512] = 512;
+}
+
+static void decode(GetByteContext *gb, RangeCoder *rc, unsigned cumFreq, unsigned freq, unsigned total_freq)
+{
+    rc->code -= cumFreq * rc->range;
+    rc->range *= freq;
+
+    while (rc->range < TOP && bytestream2_get_bytes_left(gb) > 0) {
+        unsigned byte = bytestream2_get_byte(gb);
+        rc->code = (rc->code << 8) | byte;
+        rc->range <<= 8;
+    }
+}
+
+static int get_freq(RangeCoder *rc, unsigned total_freq, unsigned *freq)
+{
+    if (total_freq == 0)
+        return AVERROR_INVALIDDATA;
+
+    rc->range = rc->range / total_freq;
+
+    if (rc->range == 0)
+        return AVERROR_INVALIDDATA;
+
+    *freq = rc->code / rc->range;
+
+    return 0;
+}
+
+static int decode_value(SCPRContext *s, unsigned *cnt, unsigned maxc, unsigned step, unsigned *rval)
+{
+    GetByteContext *gb = &s->gb;
+    RangeCoder *rc = &s->rc;
+    unsigned totfr = cnt[maxc];
+    unsigned value;
+    unsigned c = 0, cumfr = 0, cnt_c = 0;
+    int i, ret;
+
+    if ((ret = get_freq(rc, totfr, &value)) < 0)
+        return ret;
+
+    while (c < maxc) {
+        cnt_c = cnt[c];
+        if (value >= cumfr + cnt_c)
+            cumfr += cnt_c;
+        else
+            break;
+        c++;
+    }
+    decode(gb, rc, cumfr, cnt_c, totfr);
+
+    cnt[c] = cnt_c + step;
+    totfr += step;
+    if (totfr > BOT) {
+        totfr = 0;
+        for (i = 0; i < maxc; i++) {
+            unsigned nc = (cnt[i] >> 1) + 1;
+            cnt[i] = nc;
+            totfr += nc;
+        }
+    }
+
+    cnt[maxc] = totfr;
+    *rval = c;
+
+    return 0;
+}
+
+static int decode_unit(SCPRContext *s, PixelModel *pixel, unsigned step, unsigned *rval)
+{
+    GetByteContext *gb = &s->gb;
+    RangeCoder *rc = &s->rc;
+    unsigned totfr = pixel->total_freq;
+    unsigned value, x = 0, cumfr = 0, cnt_x = 0;
+    int i, j, ret, c, cnt_c;
+
+    if ((ret = get_freq(rc, totfr, &value)) < 0)
+        return ret;
+
+    while (x < 16) {
+        cnt_x = pixel->lookup[x];
+        if (value >= cumfr + cnt_x)
+            cumfr += cnt_x;
+        else
+            break;
+        x++;
+    }
+
+    c = x * 16;
+    cnt_c = 0;
+    while (c < 256) {
+        cnt_c = pixel->freq[c];
+        if (value >= cumfr + cnt_c)
+            cumfr += cnt_c;
+        else
+            break;
+        c++;
+    }
+    decode(gb, rc, cumfr, cnt_c, totfr);
+    pixel->freq[c] = cnt_c + step;
+    pixel->lookup[x] = cnt_x + step;
+    totfr += step;
+    if (totfr > BOT) {
+        totfr = 0;
+        for (i = 0; i < 256; i++) {
+            unsigned nc = (pixel->freq[i] >> 1) + 1;
+            pixel->freq[i] = nc;
+            totfr += nc;
+        }
+        for (i = 0; i < 16; i++) {
+            unsigned sum = 0;
+            unsigned i16_17 = i << 4;
+            for (j = 0; j < 16; j++)
+                sum += pixel->freq[i16_17 + j];
+            pixel->lookup[i] = sum;
+        }
+    }
+    pixel->total_freq = totfr;
+
+    *rval = c;
+
+    return 0;
+}
+
+static int decompress_i(AVCodecContext *avctx, uint32_t *dst, int linesize)
+{
+    SCPRContext *s = avctx->priv_data;
+    GetByteContext *gb = &s->gb;
+    int cx = 0, cx1 = 0, k = 0, clr = 0;
+    int run, r, g, b, off, y = 0, x = 0, ret;
+    const int cxshift = s->cxshift;
+    unsigned lx, ly, ptype;
+
+    reinit_tables(s);
+    bytestream2_skip(gb, 2);
+    init_rangecoder(&s->rc, gb);
+
+    while (k < avctx->width + 1) {
+        ret = decode_unit(s, &s->pixel_model[0][cx + cx1], 400, &r);
+        if (ret < 0)
+            return ret;
+
+        cx1 = (cx << 6) & 0xFC0;
+        cx = r >> cxshift;
+        ret = decode_unit(s, &s->pixel_model[1][cx + cx1], 400, &g);
+        if (ret < 0)
+            return ret;
+
+        cx1 = (cx << 6) & 0xFC0;
+        cx = g >> cxshift;
+        ret = decode_unit(s, &s->pixel_model[2][cx + cx1], 400, &b);
+        if (ret < 0)
+            return ret;
+
+        cx1 = (cx << 6) & 0xFC0;
+        cx = b >> cxshift;
+
+        ret = decode_value(s, s->run_model[0], 256, 400, &run);
+        if (ret < 0)
+            return ret;
+
+        clr = (b << 16) + (g << 8) + r;
+        k += run;
+        while (run-- > 0) {
+            dst[y * linesize + x] = clr;
+            lx = x;
+            ly = y;
+            x++;
+            if (x >= avctx->width) {
+                x = 0;
+                y++;
+            }
+        }
+    }
+    off = -linesize - 1;
+    ptype = 0;
+
+    while (x < avctx->width && y < avctx->height) {
+        ret = decode_value(s, s->op_model[ptype], 6, 1000, &ptype);
+        if (ret < 0)
+            return ret;
+        if (ptype == 0) {
+            ret = decode_unit(s, &s->pixel_model[0][cx + cx1], 400, &r);
+            if (ret < 0)
+                return ret;
+
+            cx1 = (cx << 6) & 0xFC0;
+            cx = r >> cxshift;
+            ret = decode_unit(s, &s->pixel_model[1][cx + cx1], 400, &g);
+            if (ret < 0)
+                return ret;
+
+            cx1 = (cx << 6) & 0xFC0;
+            cx = g >> cxshift;
+            ret = decode_unit(s, &s->pixel_model[2][cx + cx1], 400, &b);
+            if (ret < 0)
+                return ret;
+
+            cx1 = (cx << 6) & 0xFC0;
+            cx = b >> cxshift;
+            clr = (b << 16) + (g << 8) + r;
+        }
+        if (ptype > 5)
+            return AVERROR_INVALIDDATA;
+        ret = decode_value(s, s->run_model[ptype], 256, 400, &run);
+        if (ret < 0)
+            return ret;
+
+        switch (ptype) {
+        case 0:
+            while (run-- > 0) {
+                dst[y * linesize + x] = clr;
+                lx = x;
+                ly = y;
+                x++;
+                if (x >= avctx->width) {
+                    x = 0;
+                    y++;
+                }
+            }
+            break;
+        case 1:
+            while (run-- > 0) {
+                dst[y * linesize + x] = dst[ly * linesize + lx];
+                lx = x;
+                ly = y;
+                x++;
+                if (x >= avctx->width) {
+                    x = 0;
+                    y++;
+                }
+            }
+            clr = dst[ly * linesize + lx];
+            break;
+        case 2:
+            while (run-- > 0) {
+                clr = dst[y * linesize + x + off + 1];
+                dst[y * linesize + x] = clr;
+                lx = x;
+                ly = y;
+                x++;
+                if (x >= avctx->width) {
+                    x = 0;
+                    y++;
+                }
+            }
+            break;
+        case 4:
+            while (run-- > 0) {
+                uint8_t *odst = (uint8_t *)dst;
+                r = odst[(ly * linesize + lx) * 4] +
+                    odst[((y * linesize + x) + off) * 4 + 4] -
+                    odst[((y * linesize + x) + off) * 4];
+                g = odst[(ly * linesize + lx) * 4 + 1] +
+                    odst[((y * linesize + x) + off) * 4 + 5] -
+                    odst[((y * linesize + x) + off) * 4 + 1];
+                b = odst[(ly * linesize + lx) * 4 + 2] +
+                    odst[((y * linesize + x) + off) * 4 + 6] -
+                    odst[((y * linesize + x) + off) * 4 + 2];
+                clr = ((b & 0xFF) << 16) + ((g & 0xFF) << 8) + (r & 0xFF);
+                dst[y * linesize + x] = clr;
+                lx = x;
+                ly = y;
+                x++;
+                if (x >= avctx->width) {
+                    x = 0;
+                    y++;
+                }
+            }
+            break;
+        case 5:
+            while (run-- > 0) {
+                clr = dst[y * linesize + x + off];
+                dst[y * linesize + x] = clr;
+                lx = x;
+                ly = y;
+                x++;
+                if (x >= avctx->width) {
+                    x = 0;
+                    y++;
+                }
+            }
+            break;
+        }
+
+        if (avctx->bits_per_coded_sample == 16) {
+            cx1 = (clr & 0xFF00) >> 2;
+            cx = (clr & 0xFFFFFF) >> 16;
+        } else {
+            cx1 = (clr & 0xFC00) >> 4;
+            cx = (clr & 0xFFFFFF) >> 18;
+        }
+    }
+
+    return 0;
+}
+
+static int decompress_p(AVCodecContext *avctx,
+                        uint32_t *dst, int linesize,
+                        uint32_t *prev, int plinesize)
+{
+    SCPRContext *s = avctx->priv_data;
+    GetByteContext *gb = &s->gb;
+    int ret, temp, min, max, x, y, cx = 0, cx1 = 0;
+    int backstep = linesize - avctx->width;
+    const int cxshift = s->cxshift;
+
+    if (bytestream2_get_byte(gb) == 0)
+        return 0;
+    bytestream2_skip(gb, 1);
+    init_rangecoder(&s->rc, gb);
+
+    ret  = decode_value(s, s->range_model, 256, 1, &min);
+    ret |= decode_value(s, s->range_model, 256, 1, &temp);
+    min += temp << 8;
+    ret |= decode_value(s, s->range_model, 256, 1, &max);
+    ret |= decode_value(s, s->range_model, 256, 1, &temp);
+    if (ret < 0)
+        return ret;
+
+    max += temp << 8;
+    memset(s->blocks, 0, sizeof(*s->blocks) * s->nbcount);
+
+    while (min <= max) {
+        int fill, count;
+
+        ret  = decode_value(s, s->fill_model,  5,   10, &fill);
+        ret |= decode_value(s, s->count_model, 256, 20, &count);
+        if (ret < 0)
+            return ret;
+
+        while (min < s->nbcount && count-- > 0) {
+            s->blocks[min++] = fill;
+        }
+    }
+
+    for (y = 0; y < s->nby; y++) {
+        for (x = 0; x < s->nbx; x++) {
+            int sy1 = 0, sy2 = 16, sx1 = 0, sx2 = 16;
+
+            if (s->blocks[y * s->nbx + x] == 0)
+                continue;
+
+            if (((s->blocks[y * s->nbx + x] - 1) & 1) > 0) {
+                ret  = decode_value(s, s->sxy_model[0], 16, 100, &sx1);
+                ret |= decode_value(s, s->sxy_model[1], 16, 100, &sy1);
+                ret |= decode_value(s, s->sxy_model[2], 16, 100, &sx2);
+                ret |= decode_value(s, s->sxy_model[3], 16, 100, &sy2);
+                if (ret < 0)
+                    return ret;
+
+                sx2++;
+                sy2++;
+            }
+            if (((s->blocks[y * s->nbx + x] - 1) & 2) > 0) {
+                int i, j, by = y * 16, bx = x * 16;
+                int mvx, mvy;
+
+                ret  = decode_value(s, s->mv_model[0], 512, 100, &mvx);
+                ret |= decode_value(s, s->mv_model[1], 512, 100, &mvy);
+                if (ret < 0)
+                    return ret;
+
+                mvx -= 256;
+                mvy -= 256;
+
+                if (by + mvy + sy1 < 0 || bx + mvx + sx1 < 0)
+                    return AVERROR_INVALIDDATA;
+
+                for (i = 0; i < sy2 - sy1 && (by + sy1 + i) < avctx->height; i++) {
+                    for (j = 0; j < sx2 - sx1 && (bx + sx1 + j) < avctx->width; j++) {
+                        dst[(by + i + sy1) * linesize + bx + sx1 + j] = prev[(by + mvy + sy1 + i) * plinesize + bx + sx1 + mvx + j];
+                    }
+                }
+            } else {
+                int run, r, g, b, z, bx = x * 16 + sx1, by = y * 16 + sy1;
+                unsigned clr, ptype = 0;
+
+                for (; by < y * 16 + sy2 && by < avctx->height;) {
+                    ret = decode_value(s, s->op_model[ptype], 6, 1000, &ptype);
+                    if (ptype == 0) {
+                        ret = decode_unit(s, &s->pixel_model[0][cx + cx1], 400, &r);
+                        if (ret < 0)
+                            return ret;
+
+                        cx1 = (cx << 6) & 0xFC0;
+                        cx = r >> cxshift;
+                        ret = decode_unit(s, &s->pixel_model[1][cx + cx1], 400, &g);
+                        if (ret < 0)
+                            return ret;
+
+                        cx1 = (cx << 6) & 0xFC0;
+                        cx = g >> cxshift;
+                        ret = decode_unit(s, &s->pixel_model[2][cx + cx1], 400, &b);
+                        if (ret < 0)
+                            return ret;
+
+                        cx1 = (cx << 6) & 0xFC0;
+                        cx = b >> cxshift;
+                        clr = (b << 16) + (g << 8) + r;
+                    }
+                    if (ptype > 5)
+                        return AVERROR_INVALIDDATA;
+                    ret = decode_value(s, s->run_model[ptype], 256, 400, &run);
+                    if (ret < 0)
+                        return ret;
+
+                    switch (ptype) {
+                    case 0:
+                        while (run-- > 0) {
+                            if (by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    case 1:
+                        while (run-- > 0) {
+                            if (bx == 0) {
+                                if (by < 1)
+                                    return AVERROR_INVALIDDATA;
+                                z = backstep;
+                            } else {
+                                z = 0;
+                            }
+
+                            if (by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            clr = dst[by * linesize + bx - 1 - z];
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    case 2:
+                        while (run-- > 0) {
+                            if (by < 1 || by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            clr = dst[(by - 1) * linesize + bx];
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    case 3:
+                        while (run-- > 0) {
+                            if (by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            clr = prev[by * linesize + bx];
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    case 4:
+                        while (run-- > 0) {
+                            uint8_t *odst = (uint8_t *)dst;
+
+                            if (by < 1 || by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            if (bx == 0) {
+                                z = backstep;
+                            } else {
+                                z = 0;
+                            }
+
+                            r = odst[((by - 1) * linesize + bx) * 4] +
+                                odst[(by * linesize + bx - 1 - z) * 4] -
+                                odst[((by - 1) * linesize + bx - 1 - z) * 4];
+                            g = odst[((by - 1) * linesize + bx) * 4 + 1] +
+                                odst[(by * linesize + bx - 1 - z) * 4 + 1] -
+                                odst[((by - 1) * linesize + bx - 1 - z) * 4 + 1];
+                            b = odst[((by - 1) * linesize + bx) * 4 + 2] +
+                                odst[(by * linesize + bx - 1 - z) * 4 + 2] -
+                                odst[((by - 1) * linesize + bx - 1 - z) * 4 + 2];
+                            clr = ((b & 0xFF) << 16) + ((g & 0xFF) << 8) + (r & 0xFF);
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    case 5:
+                        while (run-- > 0) {
+                            if (by < 1 || by >= avctx->height)
+                                return AVERROR_INVALIDDATA;
+
+                            if (bx == 0) {
+                                z = backstep;
+                            } else {
+                                z = 0;
+                            }
+
+                            clr = dst[(by - 1) * linesize + bx - 1 - z];
+                            dst[by * linesize + bx] = clr;
+                            bx++;
+                            if (bx >= x * 16 + sx2 || bx >= avctx->width) {
+                                bx = x * 16 + sx1;
+                                by++;
+                            }
+                        }
+                        break;
+                    }
+
+                    if (avctx->bits_per_coded_sample == 16) {
+                        cx1 = (clr & 0xFF00) >> 2;
+                        cx = (clr & 0xFFFFFF) >> 16;
+                    } else {
+                        cx1 = (clr & 0xFC00) >> 4;
+                        cx = (clr & 0xFFFFFF) >> 18;
+                    }
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
+                        AVPacket *avpkt)
+{
+    SCPRContext *s = avctx->priv_data;
+    GetByteContext *gb = &s->gb;
+    AVFrame *frame = data;
+    int ret, type;
+
+    if (avctx->bits_per_coded_sample == 16) {
+        if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+            return ret;
+    }
+
+    if ((ret = ff_reget_buffer(avctx, s->current_frame)) < 0)
+        return ret;
+
+    bytestream2_init(gb, avpkt->data, avpkt->size);
+
+    type = bytestream2_peek_byte(gb);
+
+    if (type == 18) {
+        frame->key_frame = 1;
+        ret = decompress_i(avctx, (uint32_t *)s->current_frame->data[0],
+                           s->current_frame->linesize[0] / 4);
+    } else if (type == 17) {
+        uint32_t clr, *dst = (uint32_t *)s->current_frame->data[0];
+        int x, y;
+
+        frame->key_frame = 1;
+        bytestream2_skip(gb, 1);
+        if (avctx->bits_per_coded_sample == 16) {
+            uint16_t value = bytestream2_get_le16(gb);
+            int r, g, b;
+
+            r = (value      ) & 31;
+            g = (value >>  5) & 31;
+            b = (value >> 10) & 31;
+            clr = (r << 16) + (g << 8) + b;
+        } else {
+            clr = bytestream2_get_le24(gb);
+        }
+        for (y = 0; y < avctx->height; y++) {
+            for (x = 0; x < avctx->width; x++) {
+                dst[x] = clr;
+            }
+            dst += s->current_frame->linesize[0] / 4;
+        }
+    } else if (type == 0 || type == 1) {
+        frame->key_frame = 0;
+
+        ret = av_frame_copy(s->current_frame, s->last_frame);
+        if (ret < 0)
+            return ret;
+
+        ret = decompress_p(avctx, (uint32_t *)s->current_frame->data[0],
+                           s->current_frame->linesize[0] / 4,
+                           (uint32_t *)s->last_frame->data[0],
+                           s->last_frame->linesize[0] / 4);
+    } else {
+        return AVERROR_PATCHWELCOME;
+    }
+
+    if (ret < 0)
+        return ret;
+
+    if (avctx->bits_per_coded_sample != 16) {
+        ret = av_frame_ref(data, s->current_frame);
+        if (ret < 0)
+            return ret;
+    } else {
+        uint8_t *dst = frame->data[0];
+        int x, y;
+
+        ret = av_frame_copy(frame, s->current_frame);
+        if (ret < 0)
+            return ret;
+
+        for (y = 0; y < avctx->height; y++) {
+            for (x = 0; x < avctx->width * 4; x++) {
+                dst[x] = dst[x] << 3;
+            }
+            dst += frame->linesize[0];
+        }
+    }
+
+    frame->pict_type = frame->key_frame ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
+
+    FFSWAP(AVFrame *, s->current_frame, s->last_frame);
+
+    frame->data[0]     += frame->linesize[0] * (avctx->height - 1);
+    frame->linesize[0] *= -1;
+
+    *got_frame = 1;
+
+    return avpkt->size;
+}
+
+static av_cold int decode_init(AVCodecContext *avctx)
+{
+    SCPRContext *s = avctx->priv_data;
+
+    switch (avctx->bits_per_coded_sample) {
+    case 16: avctx->pix_fmt = AV_PIX_FMT_RGB0; break;
+    case 24:
+    case 32: avctx->pix_fmt = AV_PIX_FMT_BGR0; break;
+    default:
+        av_log(avctx, AV_LOG_ERROR, "Unsupported bitdepth %i\n", avctx->bits_per_coded_sample);
+        return AVERROR_INVALIDDATA;
+    }
+
+    s->cxshift = avctx->bits_per_coded_sample == 16 ? 0 : 2;
+    s->nbx = (avctx->width + 15) / 16;
+    s->nby = (avctx->height + 15) / 16;
+    s->nbcount = s->nbx * s->nby;
+    s->blocks = av_malloc_array(s->nbcount, sizeof(*s->blocks));
+    if (!s->blocks)
+        return AVERROR(ENOMEM);
+
+    s->last_frame = av_frame_alloc();
+    s->current_frame = av_frame_alloc();
+    if (!s->last_frame || !s->current_frame)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static av_cold int decode_close(AVCodecContext *avctx)
+{
+    SCPRContext *s = avctx->priv_data;
+
+    av_freep(&s->blocks);
+    av_frame_free(&s->last_frame);
+    av_frame_free(&s->current_frame);
+
+    return 0;
+}
+
+AVCodec ff_scpr_decoder = {
+    .name             = "scpr",
+    .long_name        = NULL_IF_CONFIG_SMALL("ScreenPressor"),
+    .type             = AVMEDIA_TYPE_VIDEO,
+    .id               = AV_CODEC_ID_SCPR,
+    .priv_data_size   = sizeof(SCPRContext),
+    .init             = decode_init,
+    .close            = decode_close,
+    .decode           = decode_frame,
+    .capabilities     = AV_CODEC_CAP_DR1,
+    .caps_internal    = FF_CODEC_CAP_INIT_THREADSAFE |
+                        FF_CODEC_CAP_INIT_CLEANUP,
+};