diff --git a/libavformat/wvenc.c b/libavformat/wvenc.c
index d225ed4280..3cc0a50c2d 100644
--- a/libavformat/wvenc.c
+++ b/libavformat/wvenc.c
@@ -19,19 +19,21 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/intreadwrite.h"
 #include "avformat.h"
 #include "internal.h"
 #include "avio_internal.h"
 #include "apetag.h"
 
+#define WV_EXTRA_SIZE 12
+#define WV_END_BLOCK  0x1000
+
 typedef struct{
     uint32_t duration;
-    int off;
 } WVMuxContext;
 
 static int write_header(AVFormatContext *s)
 {
-    WVMuxContext *wc = s->priv_data;
     AVCodecContext *codec = s->streams[0]->codec;
 
     if (s->nb_streams > 1) {
@@ -46,7 +48,6 @@ static int write_header(AVFormatContext *s)
         av_log_missing_feature(s, "remuxing from matroska container", 0);
         return AVERROR_PATCHWELCOME;
     }
-    wc->off = codec->channels > 2 ? 4 : 0;
     avpriv_set_pts_info(s->streams[0], 64, 1, codec->sample_rate);
 
     return 0;
@@ -55,18 +56,61 @@ static int write_header(AVFormatContext *s)
 static int write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     WVMuxContext *wc = s->priv_data;
+    AVCodecContext *codec = s->streams[0]->codec;
     AVIOContext *pb = s->pb;
+    uint64_t size;
+    uint32_t flags;
+    uint32_t left = pkt->size;
+    uint8_t *ptr = pkt->data;
+    int off = codec->channels > 2 ? 4 : 0;
 
+    /* FIXME: Simplify decoder/demuxer so bellow code can support midstream
+     *        change of stream parameters */
     wc->duration += pkt->duration;
     ffio_wfourcc(pb, "wvpk");
-    avio_wl32(pb, pkt->size + 12 + wc->off);
+    if (off) {
+        size = AV_RL32(pkt->data);
+        if (size <= 12)
+            return AVERROR_INVALIDDATA;
+        size -= 12;
+    } else {
+        size = pkt->size;
+    }
+
+    if (size + off > left)
+        return AVERROR_INVALIDDATA;
+
+    avio_wl32(pb, size + 12);
     avio_wl16(pb, 0x410);
     avio_w8(pb, 0);
     avio_w8(pb, 0);
     avio_wl32(pb, -1);
     avio_wl32(pb, pkt->pts);
-    avio_write(s->pb, pkt->data, pkt->size);
-    avio_flush(s->pb);
+    ptr += off; left -= off;
+    flags = AV_RL32(ptr + 4);
+    avio_write(pb, ptr, size);
+    ptr += size; left -= size;
+
+    while (!(flags & WV_END_BLOCK) &&
+            (left >= 4 + WV_EXTRA_SIZE)) {
+        ffio_wfourcc(pb, "wvpk");
+        size = AV_RL32(ptr);
+        ptr += 4; left -= 4;
+        if (size < 24 || size - 24 > left)
+            return AVERROR_INVALIDDATA;
+        avio_wl32(pb, size);
+        avio_wl16(pb, 0x410);
+        avio_w8(pb, 0);
+        avio_w8(pb, 0);
+        avio_wl32(pb, -1);
+        avio_wl32(pb, pkt->pts);
+        flags = AV_RL32(ptr + 4);
+        avio_write(pb, ptr, WV_EXTRA_SIZE);
+        ptr += WV_EXTRA_SIZE; left -= WV_EXTRA_SIZE;
+        avio_write(pb, ptr, size - 24);
+        ptr += size - 24; left -= size - 24;
+    }
+    avio_flush(pb);
 
     return 0;
 }