[FFmpeg-devel] avcodec: add Amuse Graphics decoder

Submitted by Paul B Mahol on Oct. 10, 2018, 11:22 a.m.

Details

Message ID 20181010112224.6523-1-onemda@gmail.com
State New
Headers show

Commit Message

Paul B Mahol Oct. 10, 2018, 11:22 a.m.
This work is partially sponsored by VideoLAN.

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

The AGM3 variant decodes with some artifacts.

---
 libavcodec/Makefile     |   1 +
 libavcodec/agm.c        | 692 ++++++++++++++++++++++++++++++++++++++++
 libavcodec/allcodecs.c  |   1 +
 libavcodec/avcodec.h    |   1 +
 libavcodec/codec_desc.c |   7 +
 libavformat/riff.c      |   2 +
 6 files changed, 704 insertions(+)
 create mode 100644 libavcodec/agm.c

Patch hide | download patch | download mbox

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index ce766aa466..3a396c2d85 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -173,6 +173,7 @@  OBJS-$(CONFIG_AC3_FIXED_DECODER)       += ac3dec_fixed.o ac3dec_data.o ac3.o kbd
 OBJS-$(CONFIG_AC3_ENCODER)             += ac3enc_float.o ac3enc.o ac3tab.o \
                                           ac3.o kbdwin.o
 OBJS-$(CONFIG_AC3_FIXED_ENCODER)       += ac3enc_fixed.o ac3enc.o ac3tab.o ac3.o
+OBJS-$(CONFIG_AGM_DECODER)             += agm.o
 OBJS-$(CONFIG_AIC_DECODER)             += aic.o
 OBJS-$(CONFIG_ALAC_DECODER)            += alac.o alac_data.o alacdsp.o
 OBJS-$(CONFIG_ALAC_ENCODER)            += alacenc.o alac_data.o
diff --git a/libavcodec/agm.c b/libavcodec/agm.c
new file mode 100644
index 0000000000..424b906eac
--- /dev/null
+++ b/libavcodec/agm.c
@@ -0,0 +1,692 @@ 
+/*
+ * Amuse Graphics Movie decoder
+ *
+ * Copyright (c) 2018 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>
+
+#define BITSTREAM_READER_LE
+
+#include "avcodec.h"
+#include "bytestream.h"
+#include "copy_block.h"
+#include "get_bits.h"
+#include "idctdsp.h"
+#include "internal.h"
+
+static const uint8_t unscaled_luma[64] = {
+    16, 11, 10, 16, 24, 40, 51, 61, 12, 12, 14, 19,
+    26, 58, 60, 55, 14, 13, 16, 24, 40, 57, 69, 56,
+    14, 17, 22, 29, 51, 87, 80, 62, 18, 22, 37, 56,
+    68,109,103, 77, 24, 35, 55, 64, 81,104,113, 92,
+    49, 64, 78, 87,103,121,120,101, 72, 92, 95, 98,
+    112,100,103,99
+};
+
+static const uint8_t unscaled_chroma[64] = {
+    17, 18, 24, 47, 99, 99, 99, 99, 18, 21, 26, 66,
+    99, 99, 99, 99, 24, 26, 56, 99, 99, 99, 99, 99,
+    47, 66, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99,
+    99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99,
+    99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99,
+    99, 99, 99, 99
+};
+
+typedef struct MotionVector {
+    int16_t x, y;
+} MotionVector;
+
+typedef struct AGMContext {
+    const AVClass  *class;
+    AVCodecContext *avctx;
+    GetBitContext   gb;
+    GetByteContext  gbyte;
+
+    int key_frame;
+    int bitstream_size;
+    int compression;
+    int blocks_w;
+    int blocks_h;
+    int size[3];
+    int plus;
+    int flags;
+
+    MotionVector *mvectors;
+    int           mvectors_size;
+
+    AVFrame *prev_frame;
+
+    int luma_quant_matrix[64];
+    int chroma_quant_matrix[64];
+
+    ScanTable scantable;
+    DECLARE_ALIGNED(32, int16_t, block)[64];
+    IDCTDSPContext idsp;
+} AGMContext;
+
+static int read_code2(GetBitContext *gb, int *oskip, int *level)
+{
+    int max, len = 0, skip = 0;
+
+    if (show_bits(gb, 2)) {
+        switch (show_bits(gb, 4)) {
+        case 1:
+        case 9:
+            len = 1;
+            skip = 3;
+            break;
+        case 2:
+            len = 3;
+            skip = 4;
+            break;
+        case 3:
+            len = 7;
+            skip = 4;
+            break;
+        case 5:
+        case 0xD:
+            len = 2;
+            skip = 3;
+            break;
+        case 6:
+            len = 4;
+            skip = 4;
+            break;
+        case 7:
+            len = 8;
+            skip = 4;
+            break;
+        case 0xA:
+            len = 5;
+            skip = 4;
+            break;
+        case 0xB:
+            len = 9;
+            skip = 4;
+            break;
+        case 0xE:
+            len = 6;
+            skip = 4;
+            break;
+        case 0xF:
+            len = ((show_bits(gb, 5) & 0x10) | 0xA0) >> 4;
+            skip = 5;
+            break;
+        default:
+            return AVERROR_INVALIDDATA;
+        }
+        skip_bits(gb, skip);
+        *level = get_bits(gb, len);
+        *oskip = 0;
+        max = 1 << (len - 1);
+        if (*level < max)
+            *level = -(max + *level);
+    } else if (show_bits(gb, 3) & 4) {
+        skip_bits(gb, 3);
+        if (show_bits(gb, 4)) {
+            if (show_bits(gb, 4) == 1) {
+                skip_bits(gb, 4);
+                *oskip = get_bits(gb, 16);
+                *level = 0;
+            } else {
+                *oskip = get_bits(gb, 4);
+                *level = 0;
+            }
+        } else {
+            skip_bits(gb, 4);
+            *oskip = get_bits(gb, 10);
+            *level = 0;
+        }
+    } else {
+        skip_bits(gb, 3);
+        *oskip = 0;
+        *level = 0;
+    }
+
+    return 0;
+}
+
+static int read_code(GetBitContext *gb, int *oskip, int *level, int *map)
+{
+    int len = 0, skip = 0, max;
+
+    if (show_bits(gb, 2)) {
+        switch (show_bits(gb, 4)) {
+        case 1:
+        case 9:
+            len = 1;
+            skip = 3;
+            break;
+        case 2:
+            len = 3;
+            skip = 4;
+            break;
+        case 3:
+            len = 7;
+            skip = 4;
+            break;
+        case 5:
+        case 13:
+            len = 2;
+            skip = 3;
+            break;
+        case 6:
+            len = 4;
+            skip = 4;
+            break;
+        case 7:
+            len = 8;
+            skip = 4;
+            break;
+        case 10:
+            len = 5;
+            skip = 4;
+            break;
+        case 11:
+            len = 9;
+            skip = 4;
+            break;
+        case 14:
+            len = 6;
+            skip = 4;
+            break;
+        case 15:
+            len = ((show_bits(gb, 5) & 0x10) | 0xA0) >> 4;
+            skip = 5;
+            break;
+        default:
+            return AVERROR_INVALIDDATA;
+        }
+
+        skip_bits(gb, skip);
+        *level = get_bits(gb, len);
+        *oskip = 0;
+        max = 1 << (len - 1);
+        if (*level < max)
+            *level = -(max + *level);
+        *map = 1;
+    } else if (show_bits(gb, 3) & 4) {
+        skip_bits(gb, 3);
+        *oskip = get_bits(gb, 10);
+        *level = 0;
+    } else {
+        skip_bits(gb, 3);
+        *oskip = get_bits(gb, 4);
+        *level = 0;
+    }
+
+    return 0;
+}
+
+static int decode_intra_block(AGMContext *s, GetBitContext *gb, int size,
+                              const int *quant_matrix, int *skip, int *dc_level)
+{
+    const uint8_t *scantable = s->scantable.permutated;
+    const int offset = s->plus ? 0 : 1024;
+    int16_t *block = s->block;
+    int level, ret, map = 0 ;
+
+    memset(block, 0, sizeof(s->block));
+
+    if (*skip) {
+        (*skip)--;
+    } else {
+        ret = read_code(gb, skip, &level, &map);
+        if (ret < 0)
+            return ret;
+        *dc_level += level;
+    }
+    block[scantable[0]] = offset + *dc_level * quant_matrix[0];
+
+    for (int i = 1; i < 64;) {
+        if (*skip) {
+            int rskip;
+
+            rskip = FFMIN(*skip, 64 - i);
+            i += rskip;
+            *skip -= rskip;
+        } else {
+            ret = read_code(gb, skip, &level, &map);
+            if (ret < 0)
+                return ret;
+
+            block[scantable[i]] = level * quant_matrix[i];
+            i++;
+        }
+    }
+
+    return 0;
+}
+
+static int decode_intra_plane(AGMContext *s, GetBitContext *gb, int size,
+                              const int *quant_matrix, AVFrame *frame,
+                              int plane)
+{
+    int ret, skip = 0, dc_level = 0;
+
+    if ((ret = init_get_bits8(gb, s->gbyte.buffer, size)) < 0)
+        return ret;
+
+    for (int y = 0; y < s->blocks_h; y++) {
+        for (int x = 0; x < s->blocks_w; x++) {
+            ret = decode_intra_block(s, gb, size, quant_matrix, &skip, &dc_level);
+            if (ret < 0)
+                return ret;
+
+            s->idsp.idct_put(frame->data[plane] + (s->blocks_h - 1 - y) * 8 * frame->linesize[plane] + x * 8,
+                             frame->linesize[plane], s->block);
+        }
+    }
+
+    if (get_bits_left(gb) < 0)
+        av_log(s->avctx, AV_LOG_WARNING, "overread\n");
+
+    return 0;
+}
+
+static int decode_inter_block(AGMContext *s, GetBitContext *gb, int size,
+                              const int *quant_matrix, int *skip,
+                              int *map)
+{
+    const uint8_t *scantable = s->scantable.permutated;
+    int16_t *block = s->block;
+    int level, ret;
+
+    memset(block, 0, sizeof(s->block));
+
+    for (int i = 0; i < 64;) {
+        if (*skip) {
+            int rskip;
+
+            rskip = FFMIN(*skip, 64 - i);
+            i += rskip;
+            *skip -= rskip;
+        } else {
+            ret = read_code(gb, skip, &level, map);
+            if (ret < 0)
+                return ret;
+
+            block[scantable[i]] = level * quant_matrix[i];
+            i++;
+        }
+    }
+
+    return 0;
+}
+
+static int decode_inter_plane(AGMContext *s, GetBitContext *gb, int size,
+                              const int *quant_matrix, AVFrame *frame,
+                              AVFrame *prev, int plane)
+{
+    int ret, skip = 0;
+
+    if ((ret = init_get_bits8(gb, s->gbyte.buffer, size)) < 0)
+        return ret;
+
+    if (s->flags & 2) {
+        for (int y = 0; y < s->blocks_h; y++) {
+            for (int x = 0; x < s->blocks_w; x++) {
+                int shift = plane == 0;
+                int mvpos = (y >> shift) * (s->blocks_w >> shift) + (x >> shift);
+                int mv_x = s->mvectors[mvpos].x >> !shift;
+                int mv_y = s->mvectors[mvpos].y >> !shift;
+                int min = plane ? -16 : -32;
+                int h = frame->height >> !shift;
+                int w = frame->width  >> !shift;
+                int map = 0;
+
+                ret = decode_inter_block(s, gb, size, quant_matrix, &skip, &map);
+                if (ret < 0)
+                    return ret;
+
+                if (mv_x < min) {
+                    s->idsp.idct_put(frame->data[plane] + (s->blocks_h - 1 - y) * 8 * frame->linesize[plane] + x * 8,
+                                     frame->linesize[plane], s->block);
+                } else {
+                    if (y * 8 + mv_y < 0 || y * 8 + mv_y >= h ||
+                        x * 8 + mv_x < 0 || x * 8 + mv_x >= w)
+                        return AVERROR_INVALIDDATA;
+
+                    copy_block8(frame->data[plane] + (s->blocks_h - 1 - y) * 8 * frame->linesize[plane] + x * 8,
+                                prev->data[plane] + ((s->blocks_h - 1 - y) * 8 - mv_y) * prev->linesize[plane] + (x * 8 + mv_x),
+                                frame->linesize[plane], prev->linesize[plane], 8);
+                    if (map)
+                        s->idsp.idct_add(frame->data[plane] + (s->blocks_h - 1 - y) * 8 * frame->linesize[plane] + x * 8,
+                                         frame->linesize[plane], s->block);
+                }
+            }
+        }
+    } else {
+        for (int y = 0; y < s->blocks_h; y++) {
+            for (int x = 0; x < s->blocks_w; x++) {
+                int map = 0;
+
+                ret = decode_inter_block(s, gb, size, quant_matrix, &skip, &map);
+                if (ret < 0)
+                    return ret;
+
+                if (!map)
+                    continue;
+                s->idsp.idct_add(frame->data[plane] + (s->blocks_h - 1 - y) * 8 * frame->linesize[plane] + x * 8,
+                                 frame->linesize[plane], s->block);
+            }
+        }
+    }
+
+    if (get_bits_left(gb) < 0)
+        av_log(s->avctx, AV_LOG_WARNING, "overread\n");
+
+    return 0;
+}
+
+static void compute_quant_matrix(AGMContext *s, double qscale)
+{
+    int luma[64], chroma[64];
+    double f = 1.0 - fabs(qscale);
+
+    if (!s->key_frame && (s->flags & 2)) {
+        if (qscale >= 0.0) {
+            for (int i = 0; i < 64; i++) {
+                luma[i]   = FFMAX(1, 16 * f);
+                chroma[i] = FFMAX(1, 16 * f);
+            }
+        } else {
+            for (int i = 0; i < 64; i++) {
+                luma[i]   = FFMAX(1, 16 - qscale * 32);
+                chroma[i] = FFMAX(1, 16 - qscale * 32);
+            }
+        }
+    } else {
+        if (qscale >= 0.0) {
+            for (int i = 0; i < 64; i++) {
+                luma[i]   = FFMAX(1, unscaled_luma  [(i & 7) * 8 + (i >> 3)] * f);
+                chroma[i] = FFMAX(1, unscaled_chroma[(i & 7) * 8 + (i >> 3)] * f);
+            }
+        } else {
+            for (int i = 0; i < 64; i++) {
+                luma[i]   = FFMAX(1, 255.0 - (255 - unscaled_luma  [(i & 7) * 8 + (i >> 3)]) * f);
+                chroma[i] = FFMAX(1, 255.0 - (255 - unscaled_chroma[(i & 7) * 8 + (i >> 3)]) * f);
+            }
+        }
+    }
+
+    for (int i = 0; i < 64; i++) {
+        int pos = ff_zigzag_direct[i];
+
+        s->luma_quant_matrix[i]   = luma[pos]   * ((pos / 8) & 1 ? -1 : 1);
+        s->chroma_quant_matrix[i] = chroma[pos] * ((pos / 8) & 1 ? -1 : 1);
+    }
+}
+
+static int decode_intra(AVCodecContext *avctx, GetBitContext *gb, AVFrame *frame)
+{
+    AGMContext *s = avctx->priv_data;
+    int ret;
+
+    compute_quant_matrix(s, (2 * s->compression - 100) / 100.0);
+
+    s->blocks_w = avctx->width  >> 3;
+    s->blocks_h = avctx->height >> 3;
+
+    ret = decode_intra_plane(s, gb, s->size[0], s->luma_quant_matrix, frame, 0);
+    if (ret < 0)
+        return ret;
+
+    bytestream2_skip(&s->gbyte, s->size[0]);
+
+    s->blocks_w = avctx->width  >> 4;
+    s->blocks_h = avctx->height >> 4;
+
+    ret = decode_intra_plane(s, gb, s->size[1], s->chroma_quant_matrix, frame, 2);
+    if (ret < 0)
+        return ret;
+
+    bytestream2_skip(&s->gbyte, s->size[1]);
+
+    s->blocks_w = avctx->width  >> 4;
+    s->blocks_h = avctx->height >> 4;
+
+    ret = decode_intra_plane(s, gb, s->size[2], s->chroma_quant_matrix, frame, 1);
+    if (ret < 0)
+        return ret;
+
+    return 0;
+}
+
+static int decode_motion_vectors(AVCodecContext *avctx, GetBitContext *gb)
+{
+    AGMContext *s = avctx->priv_data;
+    int nb_mvs = ((avctx->height + 15) >> 4) * ((avctx->width + 15) >> 4);
+    int ret, skip = 0, value, end;
+
+    av_fast_padded_malloc(&s->mvectors, &s->mvectors_size,
+                          nb_mvs * sizeof(*s->mvectors));
+    if (!s->mvectors)
+        return AVERROR(ENOMEM);
+
+    if ((ret = init_get_bits8(gb, s->gbyte.buffer, bytestream2_get_bytes_left(&s->gbyte) -
+                                                   (s->size[0] + s->size[1] + s->size[2]))) < 0)
+        return ret;
+
+    for (int i = 0; i < nb_mvs; i++) {
+        ret = read_code2(gb, &skip, &value);
+        if (ret < 0)
+            return ret;
+        s->mvectors[i].x = value;
+        if (skip > 0) {
+            end = i + skip;
+            i++;
+            for (; i < nb_mvs && i < end; i++)
+                s->mvectors[i].x = 0;
+            skip = 0;
+        }
+    }
+
+    for (int i = 0; i < nb_mvs; i++) {
+        ret = read_code2(gb, &skip, &value);
+        if (ret < 0)
+            return ret;
+        s->mvectors[i].y = value;
+        if (skip > 0) {
+            end = i + skip;
+            i++;
+            for (; i < nb_mvs && i < end; i++)
+                s->mvectors[i].y = 0;
+            skip = 0;
+        }
+    }
+
+    if (get_bits_left(gb) <= 0)
+        return AVERROR_INVALIDDATA;
+    skip = (get_bits_count(gb) >> 3) + 1;
+    bytestream2_skip(&s->gbyte, skip);
+
+    return 0;
+}
+
+static int decode_inter(AVCodecContext *avctx, GetBitContext *gb,
+                        AVFrame *frame, AVFrame *prev)
+{
+    AGMContext *s = avctx->priv_data;
+    int ret;
+
+    compute_quant_matrix(s, (2 * s->compression - 100) / 100.0);
+
+    if (s->flags & 2) {
+        ret = decode_motion_vectors(avctx, gb);
+        if (ret < 0)
+            return ret;
+    }
+
+    s->blocks_w = avctx->width  >> 3;
+    s->blocks_h = avctx->height >> 3;
+
+    ret = decode_inter_plane(s, gb, s->size[0], s->luma_quant_matrix, frame, prev, 0);
+    if (ret < 0)
+        return ret;
+
+    bytestream2_skip(&s->gbyte, s->size[0]);
+
+    s->blocks_w = avctx->width  >> 4;
+    s->blocks_h = avctx->height >> 4;
+
+    ret = decode_inter_plane(s, gb, s->size[1], s->chroma_quant_matrix, frame, prev, 2);
+    if (ret < 0)
+        return ret;
+
+    bytestream2_skip(&s->gbyte, s->size[1]);
+
+    s->blocks_w = avctx->width  >> 4;
+    s->blocks_h = avctx->height >> 4;
+
+    ret = decode_inter_plane(s, gb, s->size[2], s->chroma_quant_matrix, frame, prev, 1);
+    if (ret < 0)
+        return ret;
+
+    return 0;
+}
+
+static int decode_frame(AVCodecContext *avctx, void *data,
+                        int *got_frame, AVPacket *avpkt)
+{
+    AGMContext *s = avctx->priv_data;
+    GetBitContext *gb = &s->gb;
+    GetByteContext *gbyte = &s->gbyte;
+    AVFrame *frame = data;
+    int w, h, header;
+    int ret;
+
+    if (!avpkt->size)
+        return 0;
+
+    bytestream2_init(gbyte, avpkt->data, avpkt->size);
+
+    header = bytestream2_get_le32(gbyte);
+    if (header)
+        avpriv_request_sample(avctx, "header %X", header);
+    s->bitstream_size = bytestream2_get_le24(gbyte);
+    if (avpkt->size < s->bitstream_size + 8)
+        return AVERROR_INVALIDDATA;
+
+    s->key_frame = bytestream2_get_byte(gbyte) == 32;
+    frame->key_frame = s->key_frame;
+    frame->pict_type = s->key_frame ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
+
+    s->flags = 0;
+    w = bytestream2_get_le32(gbyte);
+    if (w < 0) {
+        w = -w;
+        s->flags |= 2;
+    }
+    h = bytestream2_get_le32(gbyte);
+    if (h < 0) {
+        avpriv_request_sample(avctx, "negative height");
+        h = -h;
+        s->flags |= 1;
+    }
+
+    ret = ff_set_dimensions(avctx, w, h);
+    if (ret < 0)
+        return ret;
+
+    s->compression = bytestream2_get_le32(gbyte);
+    if (s->compression < 0 || s->compression > 100)
+        return AVERROR_INVALIDDATA;
+
+    for (int i = 0; i < 3; i++)
+        s->size[i] = bytestream2_get_le32(gbyte);
+    if (32LL + s->size[0] + s->size[1] + s->size[2] > avpkt->size)
+        return AVERROR_INVALIDDATA;
+
+    if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
+        return ret;
+
+    if (frame->key_frame) {
+        ret = decode_intra(avctx, gb, frame);
+    } else {
+        if (!s->prev_frame->data[0]) {
+            av_log(avctx, AV_LOG_ERROR, "Missing reference frame.\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        if (!(s->flags & 2)) {
+            ret = av_frame_copy(frame, s->prev_frame);
+            if (ret < 0)
+                return ret;
+        }
+
+        ret = decode_inter(avctx, gb, frame, s->prev_frame);
+    }
+    if (ret < 0)
+        return ret;
+
+    av_frame_unref(s->prev_frame);
+    if ((ret = av_frame_ref(s->prev_frame, frame)) < 0)
+        return ret;
+
+    *got_frame = 1;
+
+    return avpkt->size;
+}
+
+static av_cold int decode_init(AVCodecContext *avctx)
+{
+    AGMContext *s = avctx->priv_data;
+
+    avctx->pix_fmt = AV_PIX_FMT_YUV420P;
+    s->avctx = avctx;
+    s->plus = avctx->codec_tag == MKTAG('A', 'G', 'M', '3');
+
+    ff_idctdsp_init(&s->idsp, avctx);
+    ff_init_scantable(s->idsp.idct_permutation, &s->scantable, ff_zigzag_direct);
+
+    s->prev_frame = av_frame_alloc();
+    if (!s->prev_frame)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static av_cold int decode_close(AVCodecContext *avctx)
+{
+    AGMContext *s = avctx->priv_data;
+
+    av_frame_free(&s->prev_frame);
+    av_freep(&s->mvectors);
+    s->mvectors_size = 0;
+
+    return 0;
+}
+
+AVCodec ff_agm_decoder = {
+    .name             = "agm",
+    .long_name        = NULL_IF_CONFIG_SMALL("Amuse Graphics Movie"),
+    .type             = AVMEDIA_TYPE_VIDEO,
+    .id               = AV_CODEC_ID_AGM,
+    .priv_data_size   = sizeof(AGMContext),
+    .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,
+};
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index c0b4d56d0d..75a023cbdf 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -35,6 +35,7 @@  extern AVCodec ff_aasc_decoder;
 extern AVCodec ff_aic_decoder;
 extern AVCodec ff_alias_pix_encoder;
 extern AVCodec ff_alias_pix_decoder;
+extern AVCodec ff_agm_decoder;
 extern AVCodec ff_amv_encoder;
 extern AVCodec ff_amv_decoder;
 extern AVCodec ff_anm_decoder;
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 705a3ce4f3..b5a7a124c6 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -452,6 +452,7 @@  enum AVCodecID {
     AV_CODEC_ID_MWSC,
     AV_CODEC_ID_WCMV,
     AV_CODEC_ID_RASC,
+    AV_CODEC_ID_AGM,
 
     /* various PCM "codecs" */
     AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 67a30542d1..35563ce0bd 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -1689,6 +1689,13 @@  static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("RemotelyAnywhere Screen Capture"),
         .props     = AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_AGM,
+        .type      = AVMEDIA_TYPE_VIDEO,
+        .name      = "agm",
+        .long_name = NULL_IF_CONFIG_SMALL("Amuse Graphics Movie"),
+        .props     = AV_CODEC_PROP_LOSSLESS | AV_CODEC_PROP_LOSSY,
+    },
 
     /* various PCM "codecs" */
     {
diff --git a/libavformat/riff.c b/libavformat/riff.c
index 3907e1a9f3..d72534ea0c 100644
--- a/libavformat/riff.c
+++ b/libavformat/riff.c
@@ -475,6 +475,8 @@  const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_MWSC,         MKTAG('M', 'W', 'S', 'C') },
     { AV_CODEC_ID_WCMV,         MKTAG('W', 'C', 'M', 'V') },
     { AV_CODEC_ID_RASC,         MKTAG('R', 'A', 'S', 'C') },
+    { AV_CODEC_ID_AGM,          MKTAG('A', 'G', 'M', '2') },
+    { AV_CODEC_ID_AGM,          MKTAG('A', 'G', 'M', '3') },
     { AV_CODEC_ID_NONE,         0 }
 };