diff --git a/libavformat/Makefile b/libavformat/Makefile
index 1555b9c2ca..dc271d1d8b 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -502,6 +502,7 @@ OBJS-$(CONFIG_SEGAFILM_DEMUXER)          += segafilm.o
 OBJS-$(CONFIG_SEGAFILM_MUXER)            += segafilmenc.o
 OBJS-$(CONFIG_SEGMENT_MUXER)             += segment.o
 OBJS-$(CONFIG_SER_DEMUXER)               += serdec.o
+OBJS-$(CONFIG_SGA_DEMUXER)               += sga.o
 OBJS-$(CONFIG_SHORTEN_DEMUXER)           += shortendec.o rawdec.o
 OBJS-$(CONFIG_SIFF_DEMUXER)              += siff.o
 OBJS-$(CONFIG_SIMBIOSIS_IMX_DEMUXER)     += imx.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 3b69423508..ade247640c 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -401,6 +401,7 @@ extern AVOutputFormat ff_segafilm_muxer;
 extern AVOutputFormat ff_segment_muxer;
 extern AVOutputFormat ff_stream_segment_muxer;
 extern AVInputFormat  ff_ser_demuxer;
+extern AVInputFormat  ff_sga_demuxer;
 extern AVInputFormat  ff_shorten_demuxer;
 extern AVInputFormat  ff_siff_demuxer;
 extern AVInputFormat  ff_simbiosis_imx_demuxer;
diff --git a/libavformat/sga.c b/libavformat/sga.c
new file mode 100644
index 0000000000..6f5b85926b
--- /dev/null
+++ b/libavformat/sga.c
@@ -0,0 +1,388 @@
+/*
+ * Digital Pictures SGA game demuxer
+ *
+ * Copyright (C) 2021 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 "libavutil/intreadwrite.h"
+#include "libavutil/avassert.h"
+#include "libavutil/internal.h"
+#include "avformat.h"
+#include "internal.h"
+#include "avio_internal.h"
+
+#define SEGA_CD_PCM_NUM 12500000
+#define SEGA_CD_PCM_DEN 786432
+
+typedef struct SGADemuxContext {
+    int video_stream_index;
+    int audio_stream_index;
+
+    uint8_t sector[65536 * 2];
+    int sector_headers;
+    int packet_size;
+    int packet_type;
+    int idx;
+    int left;
+    int64_t pkt_pos;
+} SGADemuxContext;
+
+static int sga_probe(const AVProbeData *p)
+{
+    const uint8_t *src = p->buf;
+    int score = 0, sectors = 1;
+
+    for (int i = 0; i + 12 < p->buf_size; i++) {
+        int header = AV_RB16(src + i);
+        int size   = AV_RB16(src + i + 2);
+        int cnt, skip, stream;
+        int type;
+
+        if ((header > 0x07FE && header < 0x8100) ||
+            (header > 0x8200 && header < 0xA100) ||
+            (header > 0xA200 && header < 0xC100)) {
+            if (sectors) {
+                sectors = 0;
+                score--;
+            } else {
+                score -= 10;
+            }
+        } else {
+            type = header >> 8;
+            stream = header & 0xFF;
+
+            if (type == 0xAA ||
+                type == 0xA1 ||
+                type == 0xA2 ||
+                type == 0xA3) {
+                if (size <= 12)
+                    return 0;
+                if (AV_RB16(src + i + 8) == 0)
+                    return 0;
+            } else if (type == 0xC1 ||
+                       type == 0xC6 ||
+                       type == 0xC8 ||
+                       type == 0xC9 ||
+                       type == 0xCB ||
+                       type == 0xCD ||
+                       type == 0xE7) {
+                int nb_pals = src[i + 9];
+                int tiles_w = src[i + 10];
+                int tiles_h = src[i + 11];
+
+                if (size <= 12)
+                    return 0;
+                if (nb_pals == 0 || nb_pals > 4)
+                    return 0;
+                if (tiles_w == 0 || tiles_w > 80)
+                    return 0;
+                if (tiles_h == 0 || tiles_h > 60)
+                    return 0;
+            } else if (!header) {
+                if (i <= 1)
+                    return 0;
+                if ((i & 2047) != 2047 &&
+                    (i & 2047) != 0)
+                    i = FFALIGN(i, 2048) - 1;
+                continue;
+            } else {
+                score -= 5;
+                continue;
+            }
+        }
+
+        if (sectors) {
+            cnt = size + 4;
+            skip = 0;
+            while (cnt >= 2046) {
+                skip += 2;
+                cnt -= 2046;
+            }
+
+            size += skip + 3;
+        } else {
+            size += 4;
+        }
+
+        i += size;
+        score += 10;
+
+        if (score < 0)
+            break;
+    }
+
+    return av_clip(score, 0, AVPROBE_SCORE_MAX);
+}
+
+static int sga_read_header(AVFormatContext *s)
+{
+    SGADemuxContext *sga = s->priv_data;
+    AVIOContext *pb = s->pb;
+
+    sga->sector_headers = 1;
+    sga->video_stream_index = -1;
+    sga->audio_stream_index = -1;
+    sga->idx = 0;
+
+    s->ctx_flags |= AVFMTCTX_NOHEADER;
+
+    while (!avio_feof(pb)) {
+        int header = avio_rb16(pb);
+
+        if ((header > 0x07FE && header < 0x8100) ||
+            (header > 0x8200 && header < 0xA100) ||
+            (header > 0xA200 && header < 0xC100)) {
+            sga->sector_headers = 0;
+            break;
+        }
+
+        avio_skip(pb, 2046);
+    }
+
+    avio_seek(pb, 0, SEEK_SET);
+
+    return 0;
+}
+
+static int sga_video_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret;
+
+    if (sga->packet_size <= 12)
+        return AVERROR_INVALIDDATA;
+
+    if (sga->video_stream_index == -1) {
+        AVStream *st = avformat_new_stream(s, NULL);
+        if (!st)
+            return AVERROR(ENOMEM);
+
+        st->start_time              = 0;
+        st->codecpar->codec_type    = AVMEDIA_TYPE_VIDEO;
+        st->codecpar->codec_tag     = 0;
+        st->codecpar->codec_id      = AV_CODEC_ID_SGA_VIDEO;
+        sga->video_stream_index     = st->index;
+
+        avpriv_set_pts_info(st, 64, 1, 15);
+    }
+
+    ret = av_new_packet(pkt, sga->packet_size);
+    if (ret < 0)
+        return AVERROR(ENOMEM);
+    memcpy(pkt->data, sga->sector, sga->packet_size);
+    av_assert0(sga->idx >= sga->packet_size);
+    memmove(sga->sector, sga->sector + sga->packet_size, sga->idx - sga->packet_size);
+
+    pkt->stream_index = sga->video_stream_index;
+    pkt->duration = 1;
+    pkt->pos = sga->pkt_pos;
+    pkt->flags |= AV_PKT_FLAG_KEY;
+    sga->idx -= sga->packet_size;
+    sga->packet_size = 0;
+    sga->packet_type = 0;
+
+    return 0;
+}
+
+static int sga_audio_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret;
+
+    if (sga->packet_size <= 12)
+        return AVERROR_INVALIDDATA;
+
+    if (sga->audio_stream_index == -1) {
+        AVStream *st = avformat_new_stream(s, NULL);
+        if (!st)
+            return AVERROR(ENOMEM);
+
+        st->start_time              = 0;
+        st->codecpar->codec_type    = AVMEDIA_TYPE_AUDIO;
+        st->codecpar->codec_tag     = 0;
+        st->codecpar->codec_id      = AV_CODEC_ID_PCM_SGA;
+        st->codecpar->channels      = 1;
+        st->codecpar->channel_layout= AV_CH_LAYOUT_MONO;
+        st->codecpar->sample_rate   = av_rescale(AV_RB16(sga->sector + 8),
+                                                 SEGA_CD_PCM_NUM,
+                                                 SEGA_CD_PCM_DEN);
+        sga->audio_stream_index     = st->index;
+
+        avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
+    }
+
+    ret = av_new_packet(pkt, sga->packet_size - 12);
+    if (ret < 0)
+        return AVERROR(ENOMEM);
+    memcpy(pkt->data, sga->sector + 12, sga->packet_size - 12);
+    av_assert0(sga->idx >= sga->packet_size);
+    memmove(sga->sector, sga->sector + sga->packet_size, sga->idx - sga->packet_size);
+
+    pkt->stream_index = sga->audio_stream_index;
+    pkt->duration = pkt->size;
+    pkt->pos = sga->pkt_pos;
+    pkt->flags |= AV_PKT_FLAG_KEY;
+    sga->idx -= sga->packet_size;
+    sga->packet_size = 0;
+    sga->packet_type = 0;
+
+    return 0;
+}
+
+static void update_type_size(AVFormatContext *s)
+{
+    SGADemuxContext *sga = s->priv_data;
+
+    if (sga->idx >= 4) {
+        sga->packet_type = sga->sector[0];
+        sga->packet_size = AV_RB16(sga->sector + 2) + 4;
+    }
+}
+
+static int sga_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    AVIOContext *pb = s->pb;
+    int ret = 0;
+
+    if (avio_feof(pb))
+        return AVERROR_EOF;
+
+    if (sga->packet_type == 0xCD ||
+        sga->packet_type == 0xCB ||
+        sga->packet_type == 0xC9 ||
+        sga->packet_type == 0xC8 ||
+        sga->packet_type == 0xC6 ||
+        sga->packet_type == 0xC1 ||
+        sga->packet_type == 0xE7) {
+        ret = sga_video_packet(s, pkt);
+    } else if (sga->packet_type == 0xA1 ||
+               sga->packet_type == 0xA2 ||
+               sga->packet_type == 0xA3 ||
+               sga->packet_type == 0xAA) {
+        ret = sga_audio_packet(s, pkt);
+    } else {
+        av_log(s, AV_LOG_DEBUG, "Unknown chunk: %X\n", sga->packet_type);
+        return AVERROR(EAGAIN);
+    }
+
+    return ret;
+}
+
+static int try_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret = 0;
+
+    do {
+        update_type_size(s);
+
+        if (sga->idx < sga->packet_size || sga->idx < 4)
+            return AVERROR(EAGAIN);
+
+        ret = sga_packet(s, pkt);
+        if (ret != AVERROR(EAGAIN))
+            break;
+
+        av_assert0(sga->idx > 0);
+        memmove(sga->sector, sga->sector + 1, sga->idx - 1);
+        sga->idx--;
+    } while (1);
+
+    return ret;
+}
+
+static int sga_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    AVIOContext *pb = s->pb;
+    int64_t pos;
+    int ret = 0;
+
+    sga->pkt_pos = avio_tell(pb);
+
+retry:
+    if (avio_feof(pb))
+        return AVERROR_EOF;
+
+    update_type_size(s);
+
+    pos = avio_tell(pb);
+    if (pos == 0) {
+        ret = avio_read(pb, sga->sector, 2048);
+        if (ret < 0)
+            return ret;
+        sga->idx += ret;
+    } else {
+        int packet = 0;
+
+        ret = ffio_ensure_seekback(pb, 2);
+        if (ret < 0)
+            return ret;
+        if (avio_rb16(pb) >> 15 || !sga->sector_headers) {
+            avio_seek(pb, -2, SEEK_CUR);
+
+            ret = try_packet(s, pkt);
+            packet = ret == 0;
+            if (sga->sector_headers)
+                sga->idx = sga->packet_type = sga->packet_size = 0;
+            sga->left = 2048;
+        } else {
+            sga->left = 2046;
+        }
+
+        av_assert0(sga->idx >= 0);
+        if (sga->idx + sga->left > sizeof(sga->sector))
+            return AVERROR_INVALIDDATA;
+        ret = avio_read(pb, sga->sector + sga->idx, sga->left);
+        if (ret < 0)
+            return ret;
+        sga->idx += ret;
+        if (packet)
+            return ret;
+    }
+
+    ret = try_packet(s, pkt);
+    if (ret == AVERROR(EAGAIN))
+        goto retry;
+
+    return ret;
+}
+
+static int sga_seek(AVFormatContext *s, int stream_index,
+                     int64_t timestamp, int flags)
+{
+    SGADemuxContext *sga = s->priv_data;
+
+    sga->packet_type = sga->packet_size = sga->idx = 0;
+
+    return -1;
+}
+
+AVInputFormat ff_sga_demuxer = {
+    .name           = "sga",
+    .long_name      = NULL_IF_CONFIG_SMALL("Digital Pictures SGA"),
+    .priv_data_size = sizeof(SGADemuxContext),
+    .read_probe     = sga_probe,
+    .read_header    = sga_read_header,
+    .read_packet    = sga_read_packet,
+    .read_seek      = sga_seek,
+    .extensions     = "sga",
+    .flags          = AVFMT_GENERIC_INDEX,
+};
