diff --git a/libavformat/Makefile b/libavformat/Makefile
index bc1ddfa81c..85b5d8e7eb 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -581,6 +581,7 @@ OBJS-$(CONFIG_WEBP_MUXER)                += webpenc.o
 OBJS-$(CONFIG_WEBVTT_DEMUXER)            += webvttdec.o subtitles.o
 OBJS-$(CONFIG_WEBVTT_MUXER)              += webvttenc.o
 OBJS-$(CONFIG_WSAUD_DEMUXER)             += westwood_aud.o
+OBJS-$(CONFIG_WSAUD_MUXER)               += westwood_audenc.o
 OBJS-$(CONFIG_WSD_DEMUXER)               += wsddec.o rawdec.o
 OBJS-$(CONFIG_WSVQA_DEMUXER)             += westwood_vqa.o
 OBJS-$(CONFIG_WTV_DEMUXER)               += wtvdec.o wtv_common.o \
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index fa093c7ac2..fe70a1e9a2 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -478,6 +478,7 @@ extern AVOutputFormat ff_webp_muxer;
 extern AVInputFormat  ff_webvtt_demuxer;
 extern AVOutputFormat ff_webvtt_muxer;
 extern AVInputFormat  ff_wsaud_demuxer;
+extern AVOutputFormat ff_wsaud_muxer;
 extern AVInputFormat  ff_wsd_demuxer;
 extern AVInputFormat  ff_wsvqa_demuxer;
 extern AVInputFormat  ff_wtv_demuxer;
diff --git a/libavformat/westwood_audenc.c b/libavformat/westwood_audenc.c
new file mode 100644
index 0000000000..e381aa9a1a
--- /dev/null
+++ b/libavformat/westwood_audenc.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2021 Aidan Richmond
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * Westwood Studios AUD file muxer
+ * by Aidan Richmond (aidan.is@hotmail.co.uk)
+ * 
+ * This muxer supports IMA ADPCM packed in westwoods format.
+ * 
+ * @see http://xhp.xwis.net/documents/aud3.txt
+ */
+
+#include "libavutil/avassert.h"
+
+#include "avformat.h"
+#include "avio_internal.h"
+#include "internal.h"
+#include <stdint.h>
+
+#define AUD_CHUNK_SIGNATURE 0x0000DEAF
+
+typedef struct AUDMuxContext {
+    int uncomp_size;
+    int size;
+} AUDMuxContext;
+
+static int wsaud_write_header(AVFormatContext *ctx)
+{
+    AVStream     *st = ctx->streams[0];
+    AVIOContext  *pb = ctx->pb;
+    AUDMuxContext *a = ctx->priv_data;
+    unsigned char flags = 0;
+
+    if (st->codecpar->codec_id != AV_CODEC_ID_ADPCM_IMA_WS) {
+        av_log(st, AV_LOG_ERROR, "%s codec not supported for Westwood AUD.\n",
+               avcodec_get_name(st->codecpar->codec_id));
+        return -1;
+    }
+
+    if (ctx->nb_streams != 1) {
+        av_log(st, AV_LOG_ERROR, "AUD files have exactly one stream\n");
+        return AVERROR(EINVAL);
+    }
+
+    a->uncomp_size = 0;
+    a->size = 0;
+
+    /* Flag if we have stereo data. */
+    if (st->codecpar->channels == 2)
+        flags |= 1;
+    
+    /* This flags that the file contains 16 bit samples rather than 8 bit
+       since the encoder only encodes 16 bit samples this should be set. */
+    if (av_get_bits_per_sample(st->codecpar->codec_id) == 4)
+        flags |= 2;
+
+    avio_wl16(pb, st->codecpar->sample_rate);
+    /* We don't know the file size yet, so just zero 8 bytes */
+    ffio_fill(pb, 0, 8);
+    avio_w8(pb, flags);
+    /* 99 indicates the ADPCM format. Other formats not supported. */
+    avio_w8(pb, 99);
+
+    return 0;
+}
+
+static int wsaud_write_packet(AVFormatContext *ctx, AVPacket *pkt)
+{
+    AVIOContext  *pb = ctx->pb;
+    AUDMuxContext *a = ctx->priv_data;
+    
+    av_assert1(pkt->size < UINT16_MAX && (pkt->size * 4) < UINT16_MAX);
+    /* Assumes ADPCM since this muxer doesn't support SND1 or PCM format. */
+    avio_wl16(pb, pkt->size);
+    avio_wl16(pb, pkt->size * 4);
+    avio_wl32(pb, AUD_CHUNK_SIGNATURE);
+    avio_write(pb, pkt->data, pkt->size);
+    a->size += pkt->size + 8;
+    a->uncomp_size += pkt->size * 4;
+
+    return 0;
+}
+
+static int wsaud_write_trailer(AVFormatContext *ctx)
+{
+    AVIOContext  *pb = ctx->pb;
+    AUDMuxContext *a = ctx->priv_data;
+    
+    if(!pb->seekable) {
+        av_log(ctx->streams[0], AV_LOG_ERROR, "Cannot seek to write file size to header.");
+        return -1;
+    }
+    
+    avio_seek(pb, 2, SEEK_SET);
+    avio_wl32(pb, a->size);
+    avio_wl32(pb, a->uncomp_size);
+
+    return 0;
+}
+
+AVOutputFormat ff_wsaud_muxer = {
+    .name              = "wsaud",
+    .long_name         = NULL_IF_CONFIG_SMALL("Westwood Studios audio"),
+    .extensions        = "aud",
+    .priv_data_size    = sizeof(AUDMuxContext),
+    .audio_codec       = AV_CODEC_ID_ADPCM_IMA_WS,
+    .video_codec       = AV_CODEC_ID_NONE,
+    .write_header      = wsaud_write_header,
+    .write_packet      = wsaud_write_packet,
+    .write_trailer     = wsaud_write_trailer,
+};
