diff --git a/libavformat/Makefile b/libavformat/Makefile
index 903b3ee9ce..ca4ceef54f 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -85,7 +85,7 @@ OBJS-$(CONFIG_FOURXM_DEMUXER)            += 4xm.o
 OBJS-$(CONFIG_FRAMECRC_MUXER)            += framecrcenc.o
 OBJS-$(CONFIG_FRAMEMD5_MUXER)            += md5enc.o
 OBJS-$(CONFIG_GIF_MUXER)                 += gif.o
-OBJS-$(CONFIG_GSM_DEMUXER)               += rawdec.o
+OBJS-$(CONFIG_GSM_DEMUXER)               += gsmdec.o
 OBJS-$(CONFIG_GXF_DEMUXER)               += gxf.o
 OBJS-$(CONFIG_GXF_MUXER)                 += gxfenc.o audiointerleave.o
 OBJS-$(CONFIG_G722_DEMUXER)              += rawdec.o
diff --git a/libavformat/gsmdec.c b/libavformat/gsmdec.c
new file mode 100644
index 0000000000..291e2c56aa
--- /dev/null
+++ b/libavformat/gsmdec.c
@@ -0,0 +1,135 @@
+/*
+ * RAW GSM demuxer
+ * Copyright (c) 2011 Justin Ruggles
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/mathematics.h"
+#include "libavutil/opt.h"
+#include "avformat.h"
+
+#define GSM_BLOCK_SIZE    33
+#define GSM_BLOCK_SAMPLES 160
+#define GSM_SAMPLE_RATE   8000
+
+typedef struct {
+    AVClass *class;
+    int sample_rate;
+} GSMDemuxerContext;
+
+static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    int ret, size;
+
+    size = GSM_BLOCK_SIZE * 32;
+
+    if (av_new_packet(pkt, size) < 0)
+        return AVERROR(ENOMEM);
+
+    pkt->pos = avio_tell(s->pb);
+    pkt->stream_index = 0;
+
+    ret = av_get_packet(s->pb, pkt, size);
+    if (ret < GSM_BLOCK_SIZE) {
+        av_free_packet(pkt);
+        return ret < 0 ? ret : AVERROR(EIO);
+    }
+    pkt->size     = ret;
+    pkt->duration = ret      / GSM_BLOCK_SIZE;
+    pkt->pts      = pkt->pos / GSM_BLOCK_SIZE;
+
+    return 0;
+}
+
+static int gsm_read_header(AVFormatContext *s, AVFormatParameters *ap)
+{
+    GSMDemuxerContext *c = s->priv_data;
+    AVStream *st = avformat_new_stream(s, NULL);
+    if (!st)
+        return AVERROR(ENOMEM);
+
+    st->codec->codec_type  = AVMEDIA_TYPE_AUDIO;
+    st->codec->codec_id    = s->iformat->value;
+    st->codec->channels    = 1;
+    st->codec->sample_rate = c->sample_rate;
+    st->codec->block_align = GSM_BLOCK_SIZE;
+    st->codec->bit_rate    = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;
+
+    av_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE);
+
+    return 0;
+}
+
+static int gsm_read_seek2(AVFormatContext *s, int stream_index, int64_t min_ts,
+                          int64_t ts, int64_t max_ts, int flags)
+{
+    GSMDemuxerContext *c = s->priv_data;
+
+    /* convert timestamps to file positions */
+    if (!(flags & AVSEEK_FLAG_BYTE)) {
+        if (stream_index < 0) {
+            AVRational bitrate_q = { GSM_BLOCK_SAMPLES, c->sample_rate * GSM_BLOCK_SIZE };
+            ts     = av_rescale_q(ts,     AV_TIME_BASE_Q, bitrate_q);
+            min_ts = av_rescale_q(min_ts, AV_TIME_BASE_Q, bitrate_q);
+            max_ts = av_rescale_q(max_ts, AV_TIME_BASE_Q, bitrate_q);
+        } else {
+            ts     *= GSM_BLOCK_SIZE;
+            min_ts *= GSM_BLOCK_SIZE;
+            max_ts *= GSM_BLOCK_SIZE;
+        }
+    }
+    /* round to nearest block boundary */
+    ts = (ts + GSM_BLOCK_SIZE / 2) / GSM_BLOCK_SIZE * GSM_BLOCK_SIZE;
+    ts = FFMAX(0, ts);
+
+    /* handle min/max */
+    while (ts < min_ts)
+        ts += GSM_BLOCK_SIZE;
+    while (ts > max_ts)
+        ts -= GSM_BLOCK_SIZE;
+    if (ts < min_ts || ts > max_ts)
+        return -1;
+
+    return avio_seek(s->pb, ts, SEEK_SET);
+}
+
+static const AVOption options[] = {
+    { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
+       AV_OPT_TYPE_INT, {.dbl = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
+       AV_OPT_FLAG_DECODING_PARAM },
+    { NULL },
+};
+
+static const AVClass class = {
+    .class_name = "gsm demuxer",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVInputFormat ff_gsm_demuxer = {
+    .name           = "gsm",
+    .long_name      = NULL_IF_CONFIG_SMALL("raw GSM"),
+    .priv_data_size = sizeof(GSMDemuxerContext),
+    .read_header    = gsm_read_header,
+    .read_packet    = gsm_read_packet,
+    .read_seek2     = gsm_read_seek2,
+    .extensions     = "gsm",
+    .value          = CODEC_ID_GSM,
+    .priv_class     = &class,
+};
diff --git a/libavformat/rawdec.c b/libavformat/rawdec.c
index fb3336d37c..db8a0cd62b 100644
--- a/libavformat/rawdec.c
+++ b/libavformat/rawdec.c
@@ -186,18 +186,6 @@ AVInputFormat ff_g722_demuxer = {
 };
 #endif
 
-#if CONFIG_GSM_DEMUXER
-AVInputFormat ff_gsm_demuxer = {
-    .name           = "gsm",
-    .long_name      = NULL_IF_CONFIG_SMALL("raw GSM"),
-    .read_header    = ff_raw_audio_read_header,
-    .read_packet    = ff_raw_read_partial_packet,
-    .flags= AVFMT_GENERIC_INDEX,
-    .extensions = "gsm",
-    .value = CODEC_ID_GSM,
-};
-#endif
-
 #if CONFIG_LATM_DEMUXER
 AVInputFormat ff_latm_demuxer = {
     .name           = "latm",