diff --git a/libavformat/Makefile b/libavformat/Makefile
index 95ed25e866..4b03e9fa92 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..3dfce4e11e
--- /dev/null
+++ b/libavformat/sga.c
@@ -0,0 +1,473 @@
+/*
+ * 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 sample_rate;
+    int first_audio_size;
+    int payload_size;
+    int packet_type;
+    int flags;
+    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;
+    int last_left = 0;
+    int sample_rate = -1;;
+
+    if (p->buf_size < 2048)
+        return 0;
+
+    for (int i = 0; i + 2 < p->buf_size; i += 2048) {
+        int header = AV_RB16(src + i);
+
+        if ((header > 0x07FE && header < 0x8100) ||
+            (header > 0x8200 && header < 0xA100) ||
+            (header > 0xA200 && header < 0xC100)) {
+            sectors = 0;
+            break;
+        }
+    }
+
+    for (int i = 0; i + 4 < p->buf_size;) {
+        int header = AV_RB16(src + i);
+        int left   = AV_RB16(src + i + 2);
+        int offset, type, size;
+
+        if (sectors && header && last_left <= 0) {
+            if (left <= 8)
+                return 0;
+            last_left = left;
+        } else if (sectors && header) {
+            left = header;
+            last_left -= left;
+            if (header != 0x7FE && left <= 8)
+                return 0;
+        } else if (sectors) {
+            if (left <= 8)
+                return 0;
+            i += sectors ? 2048 : left + 4;
+            last_left = 0;
+            continue;
+        }
+
+        if (sectors && (i > 0 && left < 0x7fe) &&
+            (i + left + 14 < p->buf_size)) {
+            offset = i + left + 2;
+        } else if (sectors && i > 0) {
+            i += 2048;
+            continue;
+        } else {
+            offset = 0;
+            last_left = left;
+        }
+
+        header = AV_RB16(src + offset);
+        size   = AV_RB16(src + offset + 2) + 4;
+
+        while ((header & 0xFF00) == 0) {
+            offset++;
+            if (offset + 4 >= p->buf_size)
+                break;
+            header = AV_RB16(src + offset);
+            size   = AV_RB16(src + offset + 2) + 4;
+        }
+
+        if (offset + 12 >= p->buf_size)
+            break;
+        if ((header & 0xFF) > 1)
+            return 0;
+        type = header >> 8;
+
+        if (type == 0xAA ||
+            type == 0xA1 ||
+            type == 0xA2 ||
+            type == 0xA3) {
+            int new_rate;
+
+            if (size <= 12)
+                return 0;
+            new_rate = AV_RB16(src + offset + 8);
+            if (sample_rate < 0)
+                sample_rate = new_rate;
+            if (sample_rate == 0 || new_rate != sample_rate)
+                return 0;
+            if (src[offset + 10] != 1)
+                return 0;
+
+            score += 10;
+        } else if (type == 0xC1 ||
+                   type == 0xC6 ||
+                   type == 0xC7 ||
+                   type == 0xC8 ||
+                   type == 0xC9 ||
+                   type == 0xCB ||
+                   type == 0xCD ||
+                   type == 0xE7) {
+            int nb_pals = src[offset + 9];
+            int tiles_w = src[offset + 10];
+            int tiles_h = src[offset + 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;
+
+            score += 10;
+        } else if (header == 0x7FE) {
+            ;
+        } else {
+            return 0;
+        }
+
+        i += sectors ? 2048 : size + 4;
+
+        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->first_audio_size = 0;
+    sga->video_stream_index = -1;
+    sga->audio_stream_index = -1;
+    sga->left = 2048;
+    sga->idx = 0;
+
+    s->ctx_flags |= AVFMTCTX_NOHEADER;
+
+    if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
+        while (!avio_feof(pb)) {
+            int header = avio_rb16(pb);
+            int type = header >> 8;
+            int skip = 2046;
+            int clock;
+
+            if (!sga->first_audio_size &&
+                (type == 0xAA ||
+                 type == 0xA1 ||
+                 type == 0xA2 ||
+                 type == 0xA3)) {
+                sga->first_audio_size = avio_rb16(pb);
+                avio_skip(pb, 4);
+                clock = avio_rb16(pb);
+                sga->sample_rate = av_rescale(clock,
+                                              SEGA_CD_PCM_NUM,
+                                              SEGA_CD_PCM_DEN);
+                skip -= 8;
+            }
+            if ((header > 0x07FE && header < 0x8100) ||
+                (header > 0x8200 && header < 0xA100) ||
+                (header > 0xA200 && header < 0xC100)) {
+                sga->sector_headers = 0;
+                break;
+            }
+
+            avio_skip(pb, skip);
+        }
+
+        avio_seek(pb, 0, SEEK_SET);
+    }
+
+    return 0;
+}
+
+static void print_stats(AVFormatContext *s, const char *where)
+{
+    SGADemuxContext *sga = s->priv_data;
+
+    av_log(s, AV_LOG_DEBUG, "START %s\n", where);
+    av_log(s, AV_LOG_DEBUG, "pos: %lX\n", avio_tell(s->pb));
+    av_log(s, AV_LOG_DEBUG, "idx: %X\n", sga->idx);
+    av_log(s, AV_LOG_DEBUG, "packet_type: %X\n", sga->packet_type);
+    av_log(s, AV_LOG_DEBUG, "payload_size: %X\n", sga->payload_size);
+    av_log(s, AV_LOG_DEBUG, "SECTOR: %016lX\n", AV_RB64(sga->sector));
+    av_log(s, AV_LOG_DEBUG, "stream: %X\n", sga->sector[1]);
+    av_log(s, AV_LOG_DEBUG, "END %s\n", where);
+}
+
+static void update_type_size(AVFormatContext *s)
+{
+    SGADemuxContext *sga = s->priv_data;
+
+    if (sga->idx >= 4) {
+        sga->packet_type  = sga->sector[0];
+        sga->payload_size = AV_RB16(sga->sector + 2);
+    } else {
+        sga->packet_type  = 0;
+        sga->payload_size = 0;
+    }
+}
+
+static int sga_video_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret;
+
+    if (sga->payload_size <= 8)
+        return AVERROR_INVALIDDATA;
+
+    if (sga->video_stream_index == -1) {
+        AVRational frame_rate;
+
+        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;
+
+        if (sga->first_audio_size > 0 && sga->sample_rate > 0) {
+            frame_rate.num = sga->sample_rate;
+            frame_rate.den = sga->first_audio_size;
+        } else {
+            frame_rate.num = 15;
+            frame_rate.den = 1;
+        }
+        avpriv_set_pts_info(st, 64, frame_rate.den, frame_rate.num);
+    }
+
+    ret = av_new_packet(pkt, sga->payload_size + 4);
+    if (ret < 0)
+        return AVERROR(ENOMEM);
+    memcpy(pkt->data, sga->sector, sga->payload_size + 4);
+    av_assert0(sga->idx >= sga->payload_size + 4);
+    memmove(sga->sector, sga->sector + sga->payload_size + 4, sga->idx - sga->payload_size - 4);
+
+    pkt->stream_index = sga->video_stream_index;
+    pkt->duration = 1;
+    pkt->pos = sga->pkt_pos;
+    pkt->flags |= sga->flags;
+    sga->idx -= sga->payload_size + 4;
+    sga->flags = 0;
+    update_type_size(s);
+
+    av_log(s, AV_LOG_DEBUG, "VIDEO PACKET: %d:%016lX i:%X\n", pkt->size, AV_RB64(sga->sector), sga->idx);
+
+    return 0;
+}
+
+static int sga_audio_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret;
+
+    if (sga->payload_size <= 8)
+        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->payload_size - 8);
+    if (ret < 0)
+        return AVERROR(ENOMEM);
+    memcpy(pkt->data, sga->sector + 12, sga->payload_size - 8);
+    av_assert0(sga->idx >= sga->payload_size + 4);
+    memmove(sga->sector, sga->sector + sga->payload_size + 4, sga->idx - sga->payload_size - 4);
+
+    pkt->stream_index = sga->audio_stream_index;
+    pkt->duration = pkt->size;
+    pkt->pos = sga->pkt_pos;
+    pkt->flags |= sga->flags;
+    sga->idx -= sga->payload_size + 4;
+    sga->flags = 0;
+    update_type_size(s);
+
+    av_log(s, AV_LOG_DEBUG, "AUDIO PACKET: %d:%016lX i:%X\n", pkt->size, AV_RB64(sga->sector), sga->idx);
+
+    return 0;
+}
+
+static int sga_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret = 0;
+
+    if (sga->packet_type == 0xCD ||
+        sga->packet_type == 0xCB ||
+        sga->packet_type == 0xC9 ||
+        sga->packet_type == 0xC8 ||
+        sga->packet_type == 0xC7 ||
+        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 {
+        if (sga->idx == 0)
+            return AVERROR_EOF;
+        if (sga->sector[0])
+            return AVERROR_INVALIDDATA;
+        memmove(sga->sector, sga->sector + 1, sga->idx - 1);
+        sga->idx--;
+        return AVERROR(EAGAIN);
+    }
+
+    return ret;
+}
+
+static int try_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    int ret = AVERROR(EAGAIN);
+
+    update_type_size(s);
+    if (sga->idx >= sga->payload_size + 4) {
+        print_stats(s, "before sga_packet");
+        ret = sga_packet(s, pkt);
+        print_stats(s,  "after sga_packet");
+        if (ret != AVERROR(EAGAIN))
+            return ret;
+    }
+
+    return sga->idx < sga->payload_size + 4 ? AVERROR(EAGAIN) : ret;
+}
+
+static int sga_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    SGADemuxContext *sga = s->priv_data;
+    AVIOContext *pb = s->pb;
+    int header, ret = 0;
+
+    sga->pkt_pos = avio_tell(pb);
+
+retry:
+    update_type_size(s);
+
+    print_stats(s, "start");
+    if (avio_feof(pb) &&
+        (!sga->payload_size || sga->idx < sga->payload_size + 4))
+        return AVERROR_EOF;
+
+    if (sga->idx < sga->payload_size + 4) {
+        ret = ffio_ensure_seekback(pb, 2);
+        if (ret < 0)
+            return ret;
+
+        print_stats(s, "before read header");
+        header = avio_rb16(pb);
+        if (!header) {
+            avio_skip(pb, 2046);
+            sga->left = 0;
+        } else if (!avio_feof(pb) &&
+                   ((header >> 15) ||
+                    !sga->sector_headers)) {
+            avio_seek(pb, -2, SEEK_CUR);
+            sga->flags = AV_PKT_FLAG_KEY;
+            sga->left = 2048;
+        } else {
+            sga->left = 2046;
+        }
+
+        av_assert0(sga->idx + sga->left < sizeof(sga->sector));
+        ret = avio_read(pb, sga->sector + sga->idx, sga->left);
+        if (ret > 0)
+            sga->idx += ret;
+        else if (ret != AVERROR_EOF && ret)
+            return ret;
+        print_stats(s, "after read header");
+
+        update_type_size(s);
+    }
+
+    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->payload_size = sga->idx = 0;
+    memset(sga->sector, 0, sizeof(sga->sector));
+
+    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,
+};
