diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
index 2dffe021f9..c9801f966c 100644
--- a/doc/bitstream_filters.texi
+++ b/doc/bitstream_filters.texi
@@ -186,6 +186,27 @@ ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
 Add an MJPEG A header to the bitstream, to enable decoding by
 Quicktime.
 
+@section mod_mpeg_seq_header
+
+Given an MPEG1/2 stream, this bitstream filter can be used to modify
+the sequence headers. The most common use would be to change the
+aspect ration without the need for re-encoding. Some MOD files have
+the aspect ratio incorrectly set to 4:3 (see 
+@url{https://en.wikipedia.org/wiki/MOD_and_TOD}).
+
+To set widescreen format in a mod file do this:
+
+@example
+ffmpeg -i in.mod -bsf:v mod_mpeg_seq_header=aspect_ratio=3 -codec copy out.mpeg
+@end example
+
+@table @option
+@item aspect_ratio
+Common values are 2 for 4:3 format and 3 for 16:9 (widescreen).
+@item frame_rate
+Use 2 for 24 fps and 3 for 25 fps.
+@end table
+
 @anchor{mov2textsub}
 @section mov2textsub
 
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 357fa1a361..e275eb6062 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1002,6 +1002,7 @@ OBJS-$(CONFIG_TEXT2MOVSUB_BSF)            += movsub_bsf.o
 OBJS-$(CONFIG_VP9_RAW_REORDER_BSF)        += vp9_raw_reorder_bsf.o
 OBJS-$(CONFIG_VP9_SUPERFRAME_BSF)         += vp9_superframe_bsf.o
 OBJS-$(CONFIG_VP9_SUPERFRAME_SPLIT_BSF)   += vp9_superframe_split_bsf.o
+OBJS-$(CONFIG_MOD_MPEG_SEQ_HEADER_BSF)    += mod_mpeg_seq_header_bsf.o
 
 # thread libraries
 OBJS-$(HAVE_LIBC_MSVCRT)               += file_open.o
diff --git a/libavcodec/bitstream_filters.c b/libavcodec/bitstream_filters.c
index ce34de640d..dfe46e3e0c 100644
--- a/libavcodec/bitstream_filters.c
+++ b/libavcodec/bitstream_filters.c
@@ -44,6 +44,7 @@ extern const AVBitStreamFilter ff_text2movsub_bsf;
 extern const AVBitStreamFilter ff_vp9_raw_reorder_bsf;
 extern const AVBitStreamFilter ff_vp9_superframe_bsf;
 extern const AVBitStreamFilter ff_vp9_superframe_split_bsf;
+extern const AVBitStreamFilter ff_mod_mpeg_seq_header_bsf;
 
 #include "libavcodec/bsf_list.c"
 
diff --git a/libavcodec/mod_mpeg_seq_header_bsf.c b/libavcodec/mod_mpeg_seq_header_bsf.c
new file mode 100644
index 0000000000..824197746b
--- /dev/null
+++ b/libavcodec/mod_mpeg_seq_header_bsf.c
@@ -0,0 +1,102 @@
+/*
+ * Modify MPEG Sequence Headers bitstream filter
+ * Copyright (c) 2017 David Griffiths <david.griffiths@gmail.com>
+ *
+ * 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
+ * Modify MPEG Sequence Headers bitstream filter
+ */
+
+#include "avcodec.h"
+#include "bsf.h"
+#include "internal.h"
+
+#include "libavutil/opt.h"
+
+typedef struct ModifySeqHeaderContext {
+    const AVClass *class;
+    int aspect_ratio;
+    int frame_rate;
+    int done_log;
+} ModifySeqHeaderContext;
+
+/**
+ * This filter can be used to modify the sequence headers for aspect ratio
+ * and/or frame rate without the need for transcoding.
+ */
+static int mod_mpeg_seq_header_filter(AVBSFContext *ctx, AVPacket *out)
+{
+    ModifySeqHeaderContext *s = ctx->priv_data;
+    AVPacket *in;
+    int ret;
+
+    ret = ff_bsf_get_packet(ctx, &in);
+    if (ret < 0)
+        return ret;
+
+    if (in->data[0] == 0 && in->data[1] == 0 && in->data[2] == 1 && 
+      in->data[3] == 0xb3) {
+        if (!s->done_log)
+            av_log(ctx, AV_LOG_INFO, "old aspect byte was %x\n", in->data[7]);
+        if (s->aspect_ratio != 0) {
+            in->data[7] = (s->aspect_ratio << 4) | (in->data[7] & 0xf);
+        }
+        if (s->frame_rate != 0) {
+            in->data[7] = s->frame_rate | (in->data[7] & 0xf0);
+        }
+        if (!s->done_log)
+            av_log(ctx, AV_LOG_INFO, "new aspect byte is %x\n", in->data[7]);
+        s->done_log = 1;
+    }
+
+    av_packet_move_ref(out, in);
+    av_packet_free(&in);
+
+    return 0;
+}
+
+static const enum AVCodecID codec_ids[] = {
+    AV_CODEC_ID_MPEG1VIDEO,
+    AV_CODEC_ID_MPEG2VIDEO,
+    AV_CODEC_ID_NONE,
+};
+
+#define OFFSET(x) offsetof(ModifySeqHeaderContext, x)
+static const AVOption options[] = {
+    { "aspect_ratio", NULL, OFFSET(aspect_ratio), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 14 },
+    { "frame_rate", NULL, OFFSET(frame_rate), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 8 },
+    { NULL },
+};
+
+static const AVClass mod_mpeg_seq_header_class = {
+    .class_name = "mod_mpeg_seq_header",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+
+const AVBitStreamFilter ff_mod_mpeg_seq_header_bsf = {
+    .name   = "mod_mpeg_seq_header",
+    .priv_data_size = sizeof(ModifySeqHeaderContext),
+    .priv_class     = &mod_mpeg_seq_header_class,
+    .filter = mod_mpeg_seq_header_filter,
+    .codec_ids = codec_ids,
+};
