diff --git a/libavformat/Makefile b/libavformat/Makefile
index 2c037c0b24..2b90b788c0 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -78,6 +78,7 @@ OBJS-$(CONFIG_AAX_DEMUXER)               += aaxdec.o
 OBJS-$(CONFIG_AC3_DEMUXER)               += ac3dec.o rawdec.o
 OBJS-$(CONFIG_AC3_MUXER)                 += rawenc.o
 OBJS-$(CONFIG_AC4_DEMUXER)               += ac4dec.o
+OBJS-$(CONFIG_AC4_MUXER)                 += ac4enc.o
 OBJS-$(CONFIG_ACE_DEMUXER)               += acedec.o
 OBJS-$(CONFIG_ACM_DEMUXER)               += acm.o rawdec.o
 OBJS-$(CONFIG_ACT_DEMUXER)               += act.o
diff --git a/libavformat/ac4enc.c b/libavformat/ac4enc.c
new file mode 100644
index 0000000000..aefbfc2684
--- /dev/null
+++ b/libavformat/ac4enc.c
@@ -0,0 +1,102 @@
+/*
+ * Raw AC-4 muxer
+ *
+ * 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 "libavcodec/codec_id.h"
+#include "libavcodec/codec_par.h"
+#include "libavcodec/packet.h"
+#include "libavutil/crc.h"
+#include "libavutil/opt.h"
+#include "avformat.h"
+#include "mux.h"
+
+typedef struct AC4Context {
+    AVClass *class;
+    int write_crc;
+} AC4Context;
+
+static int ac4_init(AVFormatContext *s)
+{
+    AVCodecParameters *par = s->streams[0]->codecpar;
+
+    if (s->nb_streams != 1 || par->codec_id != AV_CODEC_ID_AC4) {
+        av_log(s, AV_LOG_ERROR, "Only one AC-4 stream can be muxed by the AC-4 muxer\n");
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static int ac4_write_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    AC4Context *ac4 = s->priv_data;
+    AVIOContext *pb = s->pb;
+
+    if (!pkt->size)
+        return 0;
+
+    if (ac4->write_crc)
+        avio_wb16(pb, 0xAC41);
+    else
+        avio_wb16(pb, 0xAC40);
+
+    if (pkt->size >= 0xffff) {
+        avio_wb16(pb, 0xffff);
+        avio_wb24(pb, pkt->size);
+    } else {
+        avio_wb16(pb, pkt->size);
+    }
+
+    avio_write(pb, pkt->data, pkt->size);
+
+    if (ac4->write_crc) {
+        uint16_t crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, pkt->data, pkt->size);
+        avio_wl16(pb, crc);
+    }
+
+    return 0;
+}
+
+#define ENC AV_OPT_FLAG_ENCODING_PARAM
+#define OFFSET(obj) offsetof(AC4Context, obj)
+static const AVOption ac4_options[] = {
+    { "write_crc",  "enable checksum", OFFSET(write_crc), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, ENC},
+    { NULL },
+};
+
+static const AVClass ac4_muxer_class = {
+    .class_name     = "AC4 muxer",
+    .item_name      = av_default_item_name,
+    .option         = ac4_options,
+    .version        = LIBAVUTIL_VERSION_INT,
+};
+
+const FFOutputFormat ff_ac4_muxer = {
+    .p.name            = "ac4",
+    .p.long_name       = NULL_IF_CONFIG_SMALL("raw AC-4"),
+    .p.mime_type       = "audio/ac4",
+    .p.extensions      = "ac4",
+    .priv_data_size    = sizeof(AC4Context),
+    .p.audio_codec     = AV_CODEC_ID_AC4,
+    .p.video_codec     = AV_CODEC_ID_NONE,
+    .init              = ac4_init,
+    .write_packet      = ac4_write_packet,
+    .p.priv_class      = &ac4_muxer_class,
+    .p.flags           = AVFMT_NOTIMESTAMPS,
+};
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 70fa7f1460..f64b0870aa 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -35,6 +35,7 @@ extern const AVInputFormat  ff_aax_demuxer;
 extern const AVInputFormat  ff_ac3_demuxer;
 extern const FFOutputFormat ff_ac3_muxer;
 extern const AVInputFormat  ff_ac4_demuxer;
+extern const FFOutputFormat ff_ac4_muxer;
 extern const AVInputFormat  ff_ace_demuxer;
 extern const AVInputFormat  ff_acm_demuxer;
 extern const AVInputFormat  ff_act_demuxer;
diff --git a/libavformat/version.h b/libavformat/version.h
index 35d796d318..1b079ebce8 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR   8
+#define LIBAVFORMAT_VERSION_MINOR   9
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \